Excretory Products And Their Elimination - Class 11 Medical Biology - Extra Questions

What is excretion? How do unicellular organisms remove their wastes?

Excretion is the process of removal of the waste, which was generated from the metabolic activities and production of energy, from the body of an organism. It is an essential process for all forms of life. 
In unicellular organisms, since they do not have any specialized organs for the removal of waste materials, their wastes are removed directly through the cell membrane by the process of diffusion.


Name the basic filtration unit present in the kidney.

The basic filtration unit present in the kidney is Nephron. Each kidney has large number of these filtration units and they are packed close together.


Differentiate between the following pairs on the basis of what is mentioned in brackets:
Renal cortex and Renal medulla [Parts of the nephrons present].

 Renal Cortex Renal Medulla
A reddish brown layer of tissue between the renal capsule and the renal medullaThe innermost layer of kidney consisting of renal pyramids
Parts of nephron present in renal cortex are Malphigian corpuscle, Proximal Convoluted Tubule and Distal Convoluted TubuleParts of Nephron present in renal medulla are Medullary loop (Loop of Henle) and Collecting duct


Look at the figure given. It is a section of human kidney as seen from the front.
Is it a longitudinal section or a cross-section?

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The figure is a longitudinal section of the human kidney.


Define excretion.

The biological process involved in the removal of harmful metabolic wastes from the body is called excretion.


A loop of capillary running parallel to the Henle's loop.

The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries. A minute vessel of this network runs parallel to the Henle’s loop forming a ‘U’ shaped vasa recta. Vasa recta are absent or highly reduced in cortical nephrons.


Write the name of excretory organs and draw a labelled diagram of excretory system in humans.

The excretory organs in humans consist of the following parts:
(i) A pair of kidney
(ii) A pair of ureters
(iii) A urinary bladder
(iv) Urethra
(v) Inferior vena cava and Aorta
(vi) Renal artery and renal vein
(vii) Iliac artery and iliac vein

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What is excretion?

The process by which metabolic wastes and other non-useful, toxic wastes such as faeces are eliminated from an organism is called excretion. In vertebrates, excretion is carried out mainly by lungs, kidneys and skin.


Draw the well labelled diagram of human nephron and define haemodialysis.

In uremia blood urea level rises abnormally. It is seen in patients whose nephrons do not function properly and their metabolic wastes start accumulating in the blood. In such conditions, artificial measures are adopted for removing accumulated nitrogenous products like urea from the blood. This process is known as hemodialysis and the apparatus used is called artificial kidney or haemodialyzer.
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Fill in the blanks with appropriate words.
Desert mammals are adapted to water shortage by having nephrons with longer ..........

The desert animals have adopted the special adaptation for water retention such that more water is reabsorbed thus causing more water absorbed . The water absorption of the water is basically by the adaptation of longer henle which is useful in a absorption of more water from the cells. 
Hence the answer is henle's loop .  


Fill in the blanks with appropriate words.
The network of capillaries, enclosed in a Bowmans capsule is called ..........

The glomerulus is a network of capillaries known as tuft, located at the beginning of the nephron in the kidney. Glomerulus along with Bowman's capsule is called the malphigian body or renal corpuscle.
So the correct answer is glomerulus.


Name the different parts of a nephron.


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Very short answer type.
What are the function performed by nephrons?

Regulation of fluid balance, elimination of nitrogenous wastes, maintenance of acid-base balance.


Mark the odd one in each of the following series
Renal pelvis, medullary pyramid, renal cortex

The renal pelvis is odd one among these. 
The renal pelvis is a hollow area in the centre of each kidney. While medullary pyramid and renal cortex are part of inner and outer regions of the parenchyma of kidney respectively.


Explain the nature of excretory wastes.

The excretory wastes are mostly toxic for the body. For example, Protein metabolism leads to the production of Nitrogenous wastes like Urea in mammals, Uric acid in birds, etc.
The waste material is processed in the Liver during the Urea cycle and is eliminated from the body.


The Bowman's capsule and glomerulus together form ________ body.

The bowman's capsule and glomerulus together form  renal corpuscle


The structure and functional unit of kidney are _______.

The nephron is the microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule.


Draw a diagram to show the site of ultra-filtration and explain the process. 


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Where does Ultrafiltration process take place?

The process of ultrafiltration takes place in the Bowman's capsule of kidney. This is a cup-shaped apparatus which have podocytes at the internal surface and thus helps in the formation of the filtrate which later forms urine. 


Match the right pairs.

1. Scurvy is a disease caused by the deficiency of vitamin C.
2. Haemoglobin is the protein in Red blood cells.
3. A nephron is the basic structural and functional unit of the kidney.
4. The ovule is the seed structure that gives rise to and contains the female reproductive cell.
5. Auxin is a plant hormone responsible for apical dominance in plants.


Draw a labelled diagram of human excretory system.

The image represents the image of labelled human excretory system. 
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Draw a neat labelled diagram of the human excretory system.

This is the diagram of the human excretory system.
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Draw a labelled diagram of a nephron. State the functions of glomerulitis, distal convoluted tubule and descending limb of Henle's loop

  • The glomerulus is a capillary tuft that receives its blood supply from an afferent arteriole of the renal circulation. Here, fluid and solutes are filtered out of the blood and into the space made by Bowman’s capsule. The glomerulus is the site in the nephron where fluid and solutes are filtered out of the blood to form a glomerular filtrate.
  • The distal convoluted tubule's permeability to water is variable depending on a hormone stimulus to enable regulation of blood osmolarity, volume, pressure, and pH. Normally, it is impermeable to water and permeable to ions, driving the osmolarity of fluid even lower. However, anti-diuretic hormone (secreted from the pituitary gland as a part of homeostasis) will act on the distal convoluted tubule to increase the permeability of the tubule to water to increase water reabsorption. This example results in increased blood volume and increased blood pressure. Many other hormones will induce other important changes in the distal convoluted tubule that fulfil the other homeostatic functions of the kidney.
  • The loop of Henle consists of a descending limb and ascending limb. It transfers fluid from the proximal to the distal tubule. The descending limb is highly permeable to water but completely impermeable to ions, causing a large amount of water to be reabsorbed, which increases fluid osmolarity to about 1200 mOSm/L. 

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Name the structural and functional units of the kidney.

Nephrons are structural and functional units of the kidney. There are about 1,000,000 nephrons in each human kidney. Each nephron is composed of a renal corpuscle, the initial filtering component; and a renal tubule that processes and carries away the filtered fluid. 


The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
Name the blood vessel which contains the least amount of urea in this diagrams.
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An efferent arteriole is the blood vessel which contains the least amount of urea in this diagram.


Why do terrestrial animals excrete hypertonic urine?

Terrestrial animals need to conserve water. They lose a great amount of water because of evaporation. So, they try to get rid of their metabolic waste (urea) with a minimal amount of water lost. Hence, they excrete hypertonic urine.


The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
State the reason for the high hydrostatic pressure in the glomerulus.
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The reason for this greater pressure is that the efferent (outgoing) arteriole is narrower than the afferent (incoming) arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule.


Write short notes on ultrafiltration and selective reabsorption.

Ultrafiltration begins in the nephron in the kidney. Blood travels through a coiled structure of capillaries called the glomerulus surrounded by the Bowman's capsule. The hydrostatic pressure of the flow of blood allows small molecules within the blood to pass through the capillary membrane and through the gaps in the podocytes surrounding the Bowman's capsule. These molecules include small ions such as sodium and potassium, glucose, water, urea and amino acids. Large molecules such as erythrocytes (red blood cells) and plasma proteins cannot cross the plasma membrane due to their size. Blood is filtered so finely through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. 
Nearly 99 per cent of the filtrate has to be reabsorbed by the renal tubules. Selective reabsorption involves the reuptake of useful substances from the filtrate and occurs in the convoluted tubules (proximal and distal). The tubular epithelial cells in different segments of nephron perform this either by active or passive mechanisms. The majority of selective reabsorption occurs in the proximal convoluted tubule, which extends from the Bowman’s capsule. 


Write short notes on nephron.

Nephrons are structural and functional unit of the kidney. Each nephron in the mammalian kidney is a long tubule. At one end this tube is closed, expanded, and folded into a double-walled cuplike structure. This structure, called the renal corpuscular capsule, or Bowman’s capsule, encloses a cluster of microscopic blood vessels—capillaries—called the glomerulus. The capsule and glomerulus together constitute the renal corpuscle. Blood flows into and away from the glomerulus through tiny arteries called arterioles, which reach and leave the glomerulus through the open end of the capsule. In the renal corpuscle, fluid filters out of the blood in the glomerulus through the inner wall of the capsule and into the nephron tubule. As this filtrate passes through the tubule, its composition is altered by the secretion of certain substances into it and by the selective reabsorption of water and other constituents from it. The final product is urine, which is conveyed through the collecting tubules into the renal pelvis.


The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
Label parts 1, 2, 3, and 4.
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The parts are labelled as follows;
1. Collecting duct
2. Distal convoluted tubule
3. Loop of Henle
4. Bowman's capsule



Observe the figure :
(a) Identify A and B.
(b) How the difference in size between A and B helps in the functioning of the kidney?
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(a)
A - Afferent vessel- The afferent vessel brings blood into the glomerulus of the nephron.
B - Efferent vessel- They carry blood away from the glomerulus.
(b) The difference in the size of the two vessels causes an increase in the blood pressure in the glomerulus and enhances ultrafiltration.


List out the various excretory organs found in the following:-
a) Sponges 
b) Roundworms 
c)Annelids 
d) crustaceans 
e) Insects 
f) Flatworms 
g) Echinoderms 
h) Cnidarians 
i) Molluscs 
j) Vertebrates 

a) Sponges- Ammonia is the chief excretory product in sponges. It diffuses from cells into the water filling the canals and surrounding the sponge. From the canal system, the waste matter is carried away by the outgoing water current.
b) Roundworms -No specific excretory organ is found. Roundworms diffuse metabolic waste through there body wall.
c) Annelids- The excretory system consists of nephridia as the excretory organ which is analogous to the kidney of vertebrates.
d) Crustaceans- two types of excretory organs are found i.e antennal glands and maxillary gland.
e) Insects-Malphigian tubules.
f) Flatworms-Nephridium. 
g) Echinoderms-No specific organ, they use diffusion to get rid of there body's metabolic waste. 
h) Cnidarians- No specific excretory organ. Metabolic waste diffuses from cells into the gastrovascular cavity and then it is released to outside through mouth. 
i) Molluscs- Kidney like nephridia.
j) Vertebrates-Kidney, nephron is the structural and functional unit of the kidney.


The tube arising from the notch of the kidney on the median side and connecting behind with the urinary bladder is __________.

It is ureters that arises from the notch of the kidney on the median side and connecting behind with the urinary bladder. It carries urine. Muscle in the ureter walls constantly tighten and relax to force urine downward away from the kidneys.


Match the terms to these definitions:

(Excretion,  micturition,  hemodialysis,  ureotelic,  uricotelic,  transport maximum,  glomerular filtration rate,  osmoregulation,  renal threshold,  nephron,  countercurrent system,  ultrafiltration)

.......... is the functional unit of a kidney

Nephrons are the functional unit of a kidney. Its chief function is to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine. 
A nephron eliminates wastes from the body, regulates blood volume and blood pressure, controls levels of electrolytes and metabolites, and regulates blood pH.


What is Juxtaglomerular apparatus?

The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole.

It is located near the vascular pole of the glomerulus and its main function is to regulate blood pressure and the filtration rate of the glomerulus.

The juxtaglomerular apparatus consists of three cell types. They are the maculadensa, a part of the distal convoluted tubule of the same nephron. juxtaglomerular cells, which secrete renin, specialized smooth muscle cells of the afferent arteriole, which supplies blood to the glomerulus.



Draw a neat diagram of excretory system of human beings and label it:

(i) Left kidney

(ii) Urinary bladder


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________ is the basic functional unit of the kidney.

Nephrons is the basic functional unit of kidney. It helps in formation of urine.


A loop of capillary running parallel to the Henle's loop is known as

A loop of the capillary that runs parallel to Henle’s loop is known as vasa rectae. Vasa rectae, along with Henle’s loop, helps in maintaining a concentration gradient in the medullary interstitium.


Indicate whether the given statement is true or false. Protein-free fluid is filtered from blood plasma into the Bowman's capsule.

The statement is true. The blood enters into the glomerulus by afferent arteriole at very high pressure which filters the component of the blood. This process of filtration of the blood in the Bowman's capsule is ultrafiltration. The filtrate leaving the Bowman's capsule is very similar to blood plasma (filtrate or glomerular filtrate is composed of blood plasma minus plasma protein, i.e., it contains all the components of blood plasma except the proteins) in composition as it passes into the proximal convoluted tubule.


Match the items of column I with those of column II:
Column IColumn II
(a) Ammonotelism(i) Birds
(b) Bowman's capsule(ii) Water reabsorption
(c) Micturition(iii) Bony fish
(d) Uricotelism(iv) Urinary bladder
(e) ADH(v) Renal tubule

Answer-

Column I

Column II

(a) Ammonotelism

(iii) Bony fish

(b) Bowman’s capsule

(v) Renal tubule

(c) Micturition

(iv) Urinary bladder

(d) Uricotelism

 (i) Birds

(e) ADH 

(ii) Water reabsorption
A. Ammonotelism is a process of excretion of body wastes in the form of ammonia. Ammonia requires more amount of water to be excreted from the body. So this type of excretion is mostly seen in water living organisms like bony fishes.
B. Bowman's capsule is a cup-like sack at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine.
C. Micturition is the process of voiding of urine from the urinary bladder through the urethra. 
D. Uricotelism is a process of excretion of body wastes in the form of uric acid. Uric acid requires less amount of water to get excreted from the body. This type of excretion is seen in reptiles and birds.
E. ADH is the antidiuretic hormone that helps in increased reabsorption of water and Na+ from DCT and decreases their excretion in urine.


Copy the picture.
(a) Label the parts A, B and C.
(b) Note down the functions of B, C and D.

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(b) Function of B (Renal Vein): The deoxygenated blood is taken away from kidneys by renal vein.
Function of C (Ureters): A pair of ureters carries urine from kidneys to the urinary bladder.
Function of D (Renal Artery): This blood vessel carries oxygenated blood to the kidney.  

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Draw well labelled diagram of L.S. of human kidney.

The labelled diagram of L.S. of human kidney.


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Draw a labelled diagram of the malpighian tubules transfer section.

This is the labelled diagram of the Malpighian tubules.
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Describe the structure of renal tubule with neatly labeled diagram.

The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system.

The components of the renal tubule are:
  • Proximal convoluted tubule: The filtrate in the Bowman's space enters the first duct in the renal tubule. This duct is called the proximal convoluted tubule, which is a section of the renal tubule located in the kidney's cortex that is responsible for the reabsorption of the majority of ultrafiltrate.=
  • The next duct of the renal tubule in line to collect the scraps left by the proximal tubule is called the loop of Henle. The loop of Henle is a long duct mainly located in the kidney's medulla that creates a concentration gradient, called a countercurrent exchange system, that allows for the reabsorption of water. While the majority of water, like the rest of the ultrafiltrate, was reabsorbed by the proximal convoluted tubule, the loop of Henle is involved in absorbing even more water in order to create concentrated urine.
  • Once the filtrate passes through the thick ascending limb of Henle, it enters the distal convoluted tubule, which is a duct of the renal tubule located in the kidney's cortex that reabsorbs calcium, sodium, and chloride and regulates the pH of urine by secreting  protons and absorbing bicarbonates.

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State the exact location of the following structures.
Proximal convoluted tubule.

Proximal convoluted tubule is the part of nephron present between Bowman's capsule and the loop of Henle in the renal cortex.


Write the functions of Bowman's capsule.

The Bowman' capsule is the part of the nephron in the human kidney. Bowman's capsule carries out the function of ultra-filtration by allowing the water molecules a small molecules of other substances to pass through its selectively permeable wall. It thus forms glomerular filtrate.


a) The diagram below shows the excretory system of a human being. Study the same and then answer the questions that follow.
i) Name the parts labelled 1, 2, 3 and 4.
ii) Give the main function of the parts labelled 5, 6, 7 and 8.
iii) Name the endocrine gland which could be added in the diagram and state its location/position.
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i) 1- Posterior Vena Cava, 2- Aorta, 3. Renal artery, 4. Renal Vein
ii) Part 5 - Ureter carries urine from kidneys to the urinary bladder.
    Part 6 - Urinary bladder contains the urine until it is released out.
    Part 7 - Sphincter muscles guards the urethra.
    Part 8 - Urethra is the passage through which urine is given out of the body.
iii) The adrenal gland is located above each kidney in the form of a cap.


Draw labelled diagram of a nephron. Explain the process of urine formation.

The process of urine formation in kidneys include the following steps:
(i) Glomerular filtration - Urine formation begins when the blood is filtered by the glomerulus and enters the Bowman's capsule and the glomerular filtrate is formed. The afferent arteriole entering the glomerulus is wider than the efferent arteriole in diameter. This increases the blood pressure within the glomerulus helps in the filtration. Glomerular filtrate is formed of all blood constituents except corpuscles and plasma proteins.
(ii) Tubular reabsorption - When the glomerular filtrate comes to the proximal tubule then the essential nutrients are reabsorbed. Glucose, amino acids, water, ions like sodium, potassium, chloride, bicarbonate, magnesium, calcium are reabsorbed from the glomerular filtrate. When the filtrate finally comes to the collecting duct ADH (anti-diuretic hormone) acts and reabsorbs the excess water and decreases the urine volume.
(iii) Tubular secretion - When the glomerular filtrate is in the proximal tubule cretinine, uric acid are secreted in it. When the filtrate goes to the distal part urea, potasium ion and some hydrogen ions are secreted in it.
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Give the biological technical term for the pigment providing colour to urine.

Urochrome is the yellow pigment, derived from breakdown of heme, which is deposited in blood and then is excreted by kidney with urine. It gives colour to urine. 


If there is a fault in the function of the 'Bowman's capsule, what will happen?

Bowman's capsule is the part of the nephron. If there is a fault in the function of the Bowman's capsule, the blood will not be filtered properly. This would lead to accumulation of the nitrogenous waste products in the body. This may ultimately lead to renal problems and kidney failure. 


Draw a neat and well labelled diagram of human excretory system.


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Draw the given diagram of L.S of kidney and label the following parts.
(a) Medullary pyramid
(b) Ureter
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The image represents the two parts of the kidney. 
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Draw the diagram and label any two parts mentioned below.
(a) Bowman's capsule
(b) Glomerulus
(c) Loop of Henle
(d) Collecting duct
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The image represents the structure of the nephron and the parts are labelled. The four parts mentioned are labelled in the diagram. 
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'Master chemists' of our body are kidneys. Give reasons.

The principal excretory organs of our body are the kidneys which maintain the chemical composition of the blood. The blood is filtered by the kidney. The wastes are removed from the body by excretion. This structure is responsible for maintaining the chemical composition of the blood by removal and absorption od the various salts, amino acids, glucose and ions. Thus, the kidney is called as master chemist of our body.


What are the different stages in Urine formation? Explain what happens in those stages.

There are three different stages in the formation of urine by the filtration of blood through the nephrons. The process of urine formation in kidneys include the following steps:
(i) Glomerular filtration - Urine formation begins when the blood is filtered by the glomerulus then enters the Bowman's capsule and the glomerular filtrate is formed. The afferent arteriole entering the glomerulus is wider than the efferent arteriole in diameter. This increases the blood pressure within the glomerulus helps in the filtration. Glomerular filtrate is formed of all blood constituents except corpuscles and plasma proteins.
(ii) Tubular reabsorption - When the glomerular filtrate comes to the proximal tubule then the essential nutrients are reabsorbed. Glucose, amino acids, water, ions like sodium, potassium, chloride, bicarbonate, magnesium, calcium are reabsorbed from the glomerular filtrate. When the filtrate finally comes to the collecting duct ADH (anti-diuretic hormone) acts and reabsorbs the excess water and decreases the urine volume.
(iii) Tubular secretion - When the glomerular filtrate is in the proximal tubule creatinine, uric acid are secreted in it. When the filtrate goes to the distal part urea, potasium ion and some hydrogen ions are secreted in the form of urine.
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What are the columns of Bertini?

There are two regions in the kidney, outer cortex and the inner medulla region. The medulla contains structures like conical masses. These are known as the medullary pyramids. The pyramids project outward to form the calyces. The cortex region is extended in between the medullary pyramids to form the renal columns called as the columns of Bertini.


Which organ is known as 'Master Chemist'? Why?

The principal excretory organs of our body are the kidneys which maintain the chemical composition of the blood. The blood is filtered by the kidney. The wastes are removed from the body by excretion. This structure is responsible for maintaining the chemical composition of the blood by removal and absorption of the various salts, amino acids, glucose and ions. Thus, the kidney is called as master chemist of our body.


Define glomerular filtration.

Urine formation begins when the fluid portion of the blood is filtered by the glomerulus and enters the Bowman's capsule as glomerular filtrate. The afferent arteriole entering the glomerulus is wider than the efferent arteriole in diameter. This increases the blood pressure within the glomerulus helping in the filtration. Glomerular filtrate is formed of all blood constituents except corpuscles and plasma proteins.


Define homeostatic mechanism in a living organism.

Homeostatic mechanisms are the ability to maintain a stable condition inside the body. It is achieved by several biophysical, biochemical processes, hormonal secretions and related metabolic modifications.
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Choose the correct answer from the four alternatives given in the brackets:
The process in which metabolic wastes are removed is
(Conduction, Excretion, Respiration, all of these)

Excretion is the process by which waste products of metabolism and other non-useful materials are eliminated from an organism. It eliminates the toxic substances from the body and helps in metabolic activity. Urea is considered as the major excretory product.


Observe the chart depicting the structure of a nephron.
(i)  Mention the structures A to F
(ii) Explain the main function of a nephron.
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A. Glomeru­lus  -  Blood enters from afferent arteriole and leave through efferent arteriole. 

B. Bowman’s capsule 

C. Proximal Convoluted Tubule

D. Loop of Henle

E. Distal Convoluted Tubule

F. The Juxtaglomerular Apparatus (JGA)

The basic function of the nephron is to filter blood and remove waste substances while retaining essential substances for various biochemical processes. In the process, the nephron can also influence the pH (acid-base balance) of the blood, regulate blood pressure, maintain the blood volume and control the level of electrolytes in the body fluids.

The functions of the nephron can be discussed with regard to each part :

  • Bowman’s capsule
Collects the incoming fluid from the glomerular capillaries.
  • Proximal tubule
Sodium, chloride, water, glucose and amino acids are reabsorbed (removed from the tubules).
    Organic acids and bases like bile salts, oxalate and urate are secreted into the proximal tubule.
    • Loop of Henle
    Water is reabsorbed mainly in the descending limb and thin segment of the ascending limb.
      Sodium, calcium, chloride, magnesium and potassium are actively reabsorbed in the thick segment of the ascending limb.
      • Distal tubule
      Controls the blood flow through the glomerular capillaries and glomerular filtration of the nephron to which it belongs.
        Sodium, potassium and chloride reabsorption.
        • Collecting tubule
        Sodium, potassium and chloride reabsorption.
          Hydrogen ion secretion.


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          Draw the diagram of human excretory system and label it.


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          Draw the L.S of kidney and label the parts.


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          (i) What are the structural and functional units of kidney?
          (ii) Arrange the organs of the human excretory system in the correct order, based on the passage of urine.
          Ureter, Urethra, Kidney, Urinary bladder.

          (i) The nephrons are the structural and functional units of the kidney. Each kidney has about 1.2 million nephrons.
          (ii) Urine is formed in the kidney. Urine flows into ureters from the kidney. Then the ureter transports urine into the urinary bladder. The urethra is a long tube which connects urinary bladder to the urinary meatus for removal of urine from the body. In males, urethra travels through the penis and meet the urethral meatus located at the tip of the penis. In females, urethra connects to the urethral meatus above the vagina. The urethra is also known as the urinary opening.
          So the correct pathway or passage of urine is Kidney -->Ureter -->Urinary Bladder --> Urethra.


          Give significance of podocyte.

          The podocytes are the specialised cells with the foot like structures at the base of the Bowman's capsule. These cells provide spaces for the passage of the filtrate and formation of the glomerular filtrate. These pores allow only the solutes and smaller molecules to pass. The blood cells are prevented from flowing into the filtrate. 


          Draw a labelled diagram of excretory system of human.

          The image represents the labelled image of the human excretory system.
          662677_626736_ans_4e3740a6f5604abf8d0e177c4399b022.png


          Match the columns and find out the correct combination

          (A) Nephridia - (2)Leech -Leeches belong to the phylum Annelida.they have nephridia as excretory organs. Nephridium is functionally similar to kidneys.
          (B) Malpighian tubules - (5)Cockaroach -Malpighian tubules are excretory organs present in the cockroach. They lie freely in hemolymph. They remove excretory products from the hemolymph and open in the alimentary canal at the junction of the midgut and hindgut. In each cockroach, they are about 150 in number. 
          (C) Protonephridia- (4)Roundworm -In Roundworm pronephros are present. Proenphrons is a paired organ, consisting of a single giant nephron that processes blood filtrate produced from glomeruli. The filtrate is deposited into the coelom.
          (D) Kidneys - (3) shark -There is a pair of kidneys present as the excretory organ in the shark. The nephron is the structural and functional unit of the kidney.


          Match the columns and choose the correct combination

          (A) Ultrafiltration - Malpighian corpuscle - Malpighian corpuscle or Renal corpuscle is an initial component of the nephron. It is composed of Glomerulus and surrounding Bowman's capsule. The glomerular blood is filtered through minute pores called filtration slits present in the wall of Bowman's capsule. This phenomenon is called glomerular filtration. It is also called as ultrafiltration because relatively larger molecules like blood proteins cannot be filtered through filtration slits.
          (B) Concentration of urine - Henle's loop - Henle's loop is the component of nephron which is responsible for the concentration of urine through the countercurrent mechanism.
          (C) Transport of urine - ureter - Ureter is a long tube that connects kidney with urinary bladder. The ureter transports the urine from kidney to urinary bladder
          (D) Storage of urine - Urinary bladder - The urinary bladder is a muscular sac which receives urine through the ureter. The urinary bladder stores urine, allowing urination to be infrequent and controlled.


          Match

          the columns 

          (A) Cockroach - (2)Malphigian tubules -These are slender tubes found in the posterior region of the body
          (B) Clarias - (3) Kidneys -It helps excrete waste materials and also maintain salt and water balance.
          (C) Earthworm - (1) Nephridia -These are long thin coiled tubes found in all segments except first two.
          (D) Balanoglossus - (5) - Proboscis gland-Elongated appendage of the head used for feeding and suckling
          (E) Flatworm - (4) Flame cells -They work like a kidney and remove excretory wastes from the body.


          Select the proper option

          A) In the PCT, filtrate is isotonic to blood plasma as there is an equal exchange of ions. $${ H }^{ + }$$ and $${ NH }_{ 3 }$$ are secreted into the PCT while $${ K }^{ + }$$, $${ HCO }_{ 3 }^{ - }$$ and $${ NaCl }$$ are reabsorbed into the interstitial cells.
          B) The ascending limb of Henle's loop opens into the DCT.
          C) In the descending limb of the loop of Henle, the fluid is hypertonic to blood plasma as there is a greater concentration of ions and a lesser concentration of water.
          D) The ascending limb of the loop of Henle is impervious to water, so all the electrolytes diffuse out and the filtrate gets diluted.
          So the correct answer is 'A-4, B-1, C-2, D-3'.

          1011008_671153_ans_6a155aac6b0446f2b7193f14616580d4.jpg


          Match the items of Column I with Column II

          A. Ammonotelism is a process of excretion of body wastes in the form of ammonia.Ammonia requires more amount of water to be excreted from the body. So this type of excretion is mostly seen in water living organisms like bony fishes.
          B. Bowman's capsule is a cup-like sack at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine.
          C. Micturition is the process of voiding of urine from the urinary bladder through the urethra. 
          D. Uricotelism is a process of excretion of body wastes in the form of uric acid. Uric acid requires less amount of water to get excreted from the body. This type of excretion is seen in reptiles and birds.
          E. ADH is the antidiuretic hormone that helps in increased reabsorption of water and Na+ from DCT and decreases their excretion in urine.


          What is glomerular filtration? What is the normal filtration force in humans?

          The first step in the urine formation is the filtration of blood. which is carried out by the glomerulus and is called glomerular filtration. The amount of the filtrate formed by the kidneys per minute is called the glomerular filtration rate (GFR). The net filtration pressure is the outward pressure minus the inward pressure i.eGlomerular(blood) hydrostatic pressure-(Blood colloidal osmotic pressure+Capsular hydrostatic pressure) =55mm Hg - (30 mm HG +15 mmHg) = 10 mm Hg. Therefore the normal filtration force in humans is 10 mm Hg.


          Define Glomerular Filtration Rate (GFR)

          Glomerular filtration rate is defined as the volume of plasma filtered by all the glomeruli in a given period of time. The GFR determines the volume of fluid available to the nephron for filtration. 
          In the normal adult male , the GFR is equal to 125ml/min. In a normal adult female the GFR is 10% less.


          What is a uriniferous tubule? How does it function?

          Explanation :
          The structural and functional unit of kidney is nephron or uriniferous tubule. A nephron consists of glomerulus, Bowman's capsule ,PCT, Henle's loop, DCT , Collecting duct.
          Function of tubules in kidney:
          Proximal convoluted tubule (PCT):  Absorption of all essential nutrients,  and 70-80% of electrolytes and water helps to maintain the pH and ionic balance of body fluids by selective secretion of hydrogen ions, ammonia and potassium ion into the filtrate.
          Henle's loop -Reabsorption in this segment is minimum, it plays a significant role in maintenance of high molarity of medullary interstitial fluid.
          Distal convoluted Tubule (DCT):  conditional reabsorption of sodium ions and water take place here, and selective secretion of potassium ions and hydrogen ions to maintain the pH and sodium potassium balance in blood.
          Collecting duct :  Large amount of water is absorbed from this region to produce concentrated urine, it plays a role in maintenance of pH and ionic balance of body by selective secretion of hydrogen and potassium ions.


          Look at the figure given. It is a section of human kidney as seen from the front.
          Name the parts numbered 1-5.

          843039_7aeba83622ad46198f010db525b2f838.JPG

          The parts represented by numbers 1-5 are:

          1 represents a renal artery

          2 represents renal vein

          3 represents ureter

          4 represents cortex

          5 represents pelvis



          The diagram given is that of a structure present in a human kidney. Study the same and answer the question that follow.
          Mention the three main steps involved in the formation of the fluid from part 2.

          827224_59d16d42dfeb485cb899ee1d6b668482.jpg

          The structure represented in the diagram is of Nephron. Part 1 shows Bowman's capsule which encapsulates the glomerulus and part 2 shows collecting duct. The fluid that comes to part 2 i.e. collecting duct, is called urine.
          The three mains steps involved in the formation of urine are:
          1. Glomerular filtration or Ultrafiltration: The blood passes through glomerulus which is a bunch of capillaries encapsulated by Bowman's capsule and due to high blood pressure in the capillaries of the glomerulus, the blood pressure forces out the water and dissolved blood components through the filtration membrane. The resulting fluid is called filtrate or glomerular filtrate
          2. Selective reabsorption: From the Bowman's capsule, the glomerular filtrate enters the Proximal Convoluted Tubule or PCT. About 65% of the glomerular filtrate is reabsorbed in the PCT. These include glucose, amino acids, vitamins, hormones, sodium, potassium, chlorides etc.
          3. Tubular secretion: The substances that are not reabsorbed in the selective reabsorption excrete into the filtrate by the process of secretion. Tubular cells secrete substances like H+, K+ and ammonia into the filtrate.
          Urine is mainly formed by the tubular secretion of urea, creatinine and mineral ions.


          The diagram given is that of a structure present in a human kidney. Study the same and answer the question that follow.
          a. What is the fluid that comes to part 2 called?
          b. Name the main nitrogenous waste in it.

          827217_eed7d17998f448b5ade17da43d41990f.jpg

          The structure represented in the diagram is of Nephron. Part 1 shows Bowman's capsule which encapsulates the glomerulus and part 2 shows collecting duct.
          a. The fluid that comes to part 2 i.e. collecting duct, is called urine.
          b. The main nitrogenous waste in urine is Urea.


          The diagram given is that of a structure present in a human kidney. Study the same and answer the question that follow.
          a. What is the liquid entering part 1 called?
          b. Name two substances present in this liquid that are reabsorbed in the tubule.

          827214_bf2383fa20b5490a9ff7843d25bd23a9.jpg

          The structure represented in the diagram is of Nephron. Nephrons are the functional unit of kidney. In the given diagram of Nephron, Part 1 shows Bowman's capsule which encapsulates the glomerulus and part 2 shows collecting duct.
          a. The liquid entering part 1 i.e. Bowman's capsule is called Glomerular filtrate which is formed by the ultrafiltration of blood through glomerulus (a bunch of capillaries encapsulated by Bowman's capsule)
          b. From the Bowman's capsule, the glomerular filtrate enters the Proximal Covulated Tubule or PCT. About 65% of the glomerular filtrate is reabsorbed in the PCT. These include glucose, amino acids, vitamins, hormones, sodium, potassium, chlorides etc.


          Correct the following statement by changing the underlined word/s.
          Normal pale yellow color of the urine is due to the presence of pigment Melanin.

          Normal pale yellow colour of the urine is due to the presence of pigment urochrome. It is also called as urobilin.  


          The diagram given is that of a structure present in a human kidney. Study the same and answer the question that follow.
          Name the structure represented in the diagram.

          827212_46e75ec80e3644e9ae6ae81a01827a7e.jpg

          The structure represented in the diagram is of Nephron. Nephrons are the functional unit of kidney. A human kidney contains about 1 million nephrons. Nephrons are thin, long and much convulated tubules. Several collecting ducts from different nephrons open into main collecting duct which is called duct of Bellini. In the given diagram of Nephron, Part 1 shows Bowman's capsule which encapsulates the glomerulus and part 2 shows collecting duct.


          Name the main nitrogenous metabolic waste excreted out by mammals including humans.

          The main nitrogenous metabolic waste excreted out by mammals including humans are urea, creatinine, and uric acid.


          Define the following terms:
          (a) Ultrafiltration
          (b) Micturition
          (c) Renal pelvis
          (d) Urea
          (e) Osmoregulation

          (a) Ultrafiltration: The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent arteriole is narrower than the afferent arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultrafiltration.

          (b) Micturition: Urine is expelled from the urinary bladder through the urethra by relaxation of the sphincter muscles located at the opening of the urinary bladder into the urethra under impulse from the nervous system such a process is called micturition.

          (c)Renal pelvis: The front end of the ureter is somewhat expanded into the kidney and is called the renal pelvis.

          (d) Urea:Urea is the chief excretory product  in terrestrial animals which is excreted in the urine.

          (e) Osmoregulation: The kidney while removing wastes like urea from the blood also regulates its composition, i.e., the percentage of water and salts. This function is called osmoregulation – it implies the regulation of osmotic pressure of the blood.


          Draw a well-labelled diagram of a human excretory system. Write the functions of
          (a) Kidney
          (b) Ureter
          (c) Urinary bladder

          (a) Kidney- Kidneys filter the blood and remove nitrogenous wastes and other toxic substances from the blood and help in urine formation.
          (b) Ureter- The ureters are the tubes that carry urine from kidneys to the urinary bladder.
          (c) Urinary bladder- It is the reservoir of urine and stores urine until it is excreted out.

          807435_838042_ans_d31761b171af469d93cdf074c07d3de2.png


          Fill in the blanks in the following passage to make it a meaningful description.

          In a nephron, the ________ flows through the ________ under great pressure. The reason for this great pressure is that the __________ (outgoing) _________ is narrower than the ___________ (incoming). This high pressure causes the ___________ part of the blood to filter out from the __________ into the __________ capsule.

          In a nephron, the blood flows through the glomerulus under great pressure. The reason for this great pressure is that the efferent (outgoing) arteriole is narrower than the afferent arteriole (incoming). This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal capsule.


          Explain the terms ultrafiltration and selective absorption.

          Explanation:
          • Ultrafiltration: In this process filtering the small molecules from blood via glomerular filtrate at the site of  glomerular capsule. 
          • Selective absorption:  In selective reabsorption body reabsorbed the essential component which filtered during ultrafiltration and the body needs back them in the bloodstream so reabsorption occur example: ions, glucose and amino acids. 


          Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow:
          Name the two main organic constituents of the fluid that flows down the part labelled '3'.

          843048_d1b728f0867845f5abd6f4f5bd1c3d00.png

          Urea and creatinine are the two main organic constituents of the fluid that flows down part 3, the ureter.


          Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow:
          Name the parts numbered 1 to 5.

          843044_f4c953c38f394860a846c6a9c947a8e0.png

          The respective parts designated by numbers are as follows:

          Number 1 represents Kidney

          Number 2 represents Renal artery

          Number 3 represents Ureter

          Number 4 represents Urinary bladder

          Number 5 represents Urethra



          Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow:
          Name the structural and functional unit of the part marked '1'.

          843046_e55c436da4c949519c415f7e8ff96095.png

          The nephron is the structural and functional unit of the part 1, the kidney.


          Look at the figure given. It is a section of human kidney as seen from the front.
          Which area/part (give its name and the number given on the diagram) contains the following respectively:
          (i) Malpighian capsule
          (ii) The pyramids
          (iii) Freshly collected urine

          843040_543b28879ab946a4bcf1c9c0f89b8205.JPG

          The area or part contained are as follows:
          (i) Number 4 cortex contains the Malpighian capsule.
          (ii) Medulla contains the pyramids
          (iii) Number 5 pelvis contains freshly collected urine.


          Study the diagram given alongside and then answer the questions that follow:
          What is the technical term given to the process occurring in 2 and 3? Briefly describe the process.
          843943_dac5640f8a4b4d07be2e9bd0406adfda.JPG

          Ultrafiltration is the technical term given to the process occurring in 2 and 3.

          The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent arteriole is narrower than the afferent arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultrafiltration.



          Given alongside is the figure of certain organs and associated parts in the human body. Study the same and answer the questions that follow:
          Name all the organ-systems shown completely or even partially.

          843042_509a32c6c65245108c44320ab1a49958.png

          The organ systems shown are - the excretory system and the circulatory system.


          The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
          Name the part of the nephron which lies in the renal medulla.
          844308_16ddc2b3d28d44e480108785814c02c8.png

          Henle’s loop and collecting tubules are the parts of the nephron that lie in the renal medulla.


          The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions:
          Name the two main stages of urine formation.
          844307_171063f433614885b465c24aba632092.png

          Ultrafiltration and reabsorption are the two main stages of urine formation.


          Fill in the blanks with appropriate words.
          The yellow colour of urine is due to ..........

          Urine gets its color from a pigment called urochrome, which is created as a result of the breakdown of the dead blood cells. Urine is a yellow that varies from pale to straw-colored under normal and healthy circumstances.


          Fill in the blanks with appropriate words.
          Kidney of a mammal resembles contractile vacuole of amoeba in expelling out..........

          Contractile vacuoles are responsible for maintaining homeostasis by osmoregulation. It is a membrane-enveloped cellular organelle found in many microorganisms that periodically expands, filling with water, and then contracts to expel its content to the cell exterior. Its function is analogous to the kidney.
          So the correct excrete water ( or cellular content).


          Fill in the blanks with appropriate words.
          A condition in which the kidneys fail to form unine is called ..........

          Anurea sometimes called anuresis, is nonpassage of urine, in practice is defined as the passage of less than 100mililitres of urine in a day. Anuria is often caused by kidney failure.
          So the correct answer is anurea.


          In which part of the nephron, does filtration take place?

          The first step in urine formation is the filtration of blood, which is carried out by the glomerulus and is called glomerular filtration. 
          The glomerular capillary blood pressure causes filtration of blood through 3 layers, i.e., the endothelium of glomerular blood vessels, the epithelium of Bowman’s capsule and a basement membrane between these two layers. The epithelial cells of Bowman’s capsule called podocytes are arranged in an intricate manner so as to leave some minute spaces called filtration slits or slit pores. Blood is filtered so finely through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. 


          Very short answer type.
          Name the yellow coloured pigment present in urine.

          Urochrome, urobilin and uroerythrin are the yellow coloured pigments present in urine.


          Fill in the blanks with appropriate words.
          Glycosuria is a condition that involves the excretion of large amount of..........

          Glycosuria or glucosuria is the excretion of glucose into the urine. Ordinarily, urine contains no glucose because the kidneys are able to reabsorb all of the filtered glucose from the tubular fluid back into the bloodstream.
           So the correct answer is glycosuria.


          Write short notes on glomerular filtration rate.

          The amount of the filtrate formed by the kidneys per minute is called the glomerular filtration rate (GFR). GFR in a healthy individual is approximately 125 ml/minute, i.e., 180 litres per day. The kidneys have built-in mechanisms for the regulation of glomerular filtration rate. One such efficient mechanism is carried out by juxtaglomerular apparatus (JGA). JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.


          Mark the odd one in each of the following series
          Afferent arteriole, Henle's loop, vasa recta, efferent arteriole.

          Henle's loop is odd one among these.
          The glomerulus is a tuft of capillaries formed by the afferent arteriole – a fine branch of the renal artery. Blood from the glomerulus is carried away by an efferent arteriole. The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries. A minute vessel of this network runs parallel to the Henle’s loop forming a ‘U’ shaped vasa recta. 
          While loop of Henle is part of the renal tubule.


          Mark the odd one in each of the following series
          glomerular filtration, antidiuretic hormone, hypertonic urine, collecting duct

          Glomerular filtration is odd one among given terms.
          Antidiuretic hormone is concerned with the production of hypertonic urine. It allows reabsorption of water from latter part of tubules ( including collecting duct) for production of hypertonic urine.


          What are the different stages of urine formation? Explain the role of glomerulus of nephron-in the formation of urine.

          Urine formation involves three main processes namely, glomerular filtration, reabsorption and secretion, that takes place in different parts of the nephron. The first step in urine formation is the filtration of blood, which is carried out by the glomerulus and is called glomerular filtration. Nearly 99 per cent of the filtrate has to be reabsorbed by the renal tubules which is known as reabsorption. The tubular epithelial cells in different segments of nephron perform this either by active or passive mechanisms. Also, during urine formation, the tubular cells secrete substances like H+,K+ and ammonia into the filtrate (secretion).
          Filtration of blood, which is carried out by the glomerulus and is called glomerular filtration. On an average, 1100-1200 ml of blood is filtered by the kidneys per minute which constitute roughly 1/5th of the blood pumped out by each ventricle of the heart in a minute. The glomerular capillary blood pressure causes filtration of blood through 3 layers, i.e., the endothelium of glomerular blood vessels, the epithelium of Bowman’s capsule and a basement membrane between these two layers. The epithelial cells of Bowman’s capsule called podocytes are arranged in an intricate manner so as to leave some minute spaces called filtration slits or slit pores. Blood is filtered so finely through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. 


          Describe the structure and physiology of the kidney of a mammal.

          Structure of Kidney:- 
          Internally, the kidneys have an intricate and unique structure. The renal parenchyma can be divided into two main areas – the outer cortex and inner medulla. The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
          The apex of a renal pyramid is called a renal papilla. Each renal papilla is associated with a structure known as the minor calyx, which collects urine from the pyramids. Several minor calyces merge to form a major calyx. Urine passes through the major calyces into the renal pelvis, a flattened and funnel-shaped structure. From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage.
          The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a gateway to the kidney – the renal vessels and ureter enter/exit. 
          Physiology of kidney:-
          Kidneys filter blood in a three-step process. 
           Step:1 The nephrons filter blood that runs through the capillary network in the glomerulus. Almost all solutes, except for proteins, are filtered out into the glomerulus by a process called glomerular filtration.
           Step:2 The filtrate is collected in the renal tubules. Most of the solutes get reabsorbed in the PCT by a process called tubular reabsorption. In the loop of Henle, the filtrate continues to exchange solutes and water with the renal medulla and the peritubular capillary network. Water is also reabsorbed during this step.
           Step:3Additional solutes and wastes are secreted into the kidney tubules during tubular secretion, which is, in essence, the opposite process to tubular reabsorption. The collecting ducts collect filtrate coming from the nephrons and fuse in the medullary papillae. From here, the papillae deliver the filtrate, now called urine, into the minor calyces that eventually connect to the ureters through the renal pelvis. 




          Differentiate between the following:
          Ascending and descending limbs of Henle's loop.

          The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward, it gets diluted due to the passage of electrolytes to the medullary fluid. The descending limb of the loop of Henle is permeable to water but almost impermeable to electrolytes. This concentrates the filtrate as it moves down.


          Mark the odd one in each of the following series
          Proximal convoluted tubule, distal convoluted tubule, Henle's loop, renal corpuscle.

          Renal corpuscle is odd one among these. 
          The nephron is composed of a renal corpuscle and a renal tubule. Proximal convoluted tubule, distal convoluted tubule and Henle's loop are part of the renal tubule.


          How is the structure of kidney related to the function of excretion? Describe the process of urine formation in humans.

          Nephrons are the specialised structure in the kidney that is responsible for excretory function mainly. They are the structural and functional unit of the kidney. 
          Each nephron is made up of two parts: Renal corpuscle and renal tubule. 
          The renal corpuscle is divided into the glomerular capillaries or glomerulus and the Bowman’s capsule. It is in the renal corpuscle that the blood is filtered at high pressure. The arteriole that brings blood into the glomerulus is called the afferent arteriole whereas the artery that takes blood away from the glomerulus is known as the efferent arteriole.
          Between these arterioles forms, a network of capillaries called the glomerular capillaries or the glomerulus. The Bowman’s capsule is a cup-shaped structure in which this glomerulus is located. The glomerulus along with the Bowman’s capsule achieve the filtration of blood to form urine. The renal tubule consists of :
          • The proximal convoluted Tubule(PCT)
          • The U-shaped Loop Of Henle
          • The Distal Convoluted Tubule(DCT)
          Once the blood is filtered in the renal corpuscle, the resultant fluid is called as the glomerular filtrate. This glomerular filtrate now passes into the PCT. In the PCT, substances like NaCl, K+, water, glucose, and bicarbonate are reabsorbed into the filtrate whereas urea, creatinine, uric acid are added to the filtrate. From the PCT, the filtrate enters the U-shaped Loop of Henle where reabsorption and secretion of water and various metabolites occurs. The filtrate then passes into the DCT. From the DCT, the filtrate passes into the collecting tubules, into the renal pelvis and the ureters as urine to be stored int he urinary bladder.
          Urine formation is a three-step process. 
          Step:1 The nephrons filter blood that runs through the capillary network in the glomerulus. Almost all solutes, except for proteins, are filtered out into the glomerulus by a process called glomerular filtration.
           Step:2 The filtrate is collected in the renal tubules. Most of the solutes get reabsorbed in the PCT by a process called tubular reabsorption. In the loop of Henle, the filtrate continues to exchange solutes and water with the renal medulla and the peritubular capillary network. Water is also reabsorbed during this step.
           Step:3Additional solutes and wastes are secreted into the kidney tubules during tubular secretion, which is, in essence, the opposite process to tubular reabsorption. The collecting ducts collect filtrate coming from the nephrons and fuse in the medullary papillae. From here, the papillae deliver the filtrate, now called urine, into the minor calyces that eventually connect to the ureters through the renal pelvis. 




          What happens to glomerular filtration rake (GF1t) if blood pressure in the kidneys increases?

          Glomerular filtration occurs due to the pressure gradient in the glomerulus. The rate at which kidneys filter blood is called the glomerular filtration rate. The main driving force for the filtering process or outward pressure is the blood pressure as it enters the glomerulus. Increased blood volume and increased blood pressure will increase GFR.


          The concentration of glucose in plasma is 100 mg/100 mL, and the GFR is 125 mL/min. How much glucose is filtered per minute?

          All of the glucose presents is filtered by glomerulus. Hence, all of the glucose that reaches glomerular in one minute with 125 ml of plasma (as GFR is 125ml/min ) is filtered. 
          i.e. 100 ml of plasma contains 100 mg of glucose, 125 ml of plasma that is being filtered will contain 125 mg of glucose. Hence, 125 ml of glucose is filtered per minute.


          Why is that the urine excreted during summer months is hypertonic?

          A lot of water is lost by sweating during summers. The body needs to conserve water at such times. Hence urine is produced with minimal loss of water i.e. hypertonic urine. Antidiuretic hormone (ADH) helps in this.


          Draw a labelled histological diagram of the kidney. Describe how selective reabsorption takes place in the kidney tubule.

          Selective reabsorption takes place in the proximal convoluted tubule (PCT) of the kidney. It is the process by which useful substances within the glomerular filtrate (such as glucose, amino acids, vitamins and water) are taken back into the blood after ultrafiltration. As only certain substances are reabsorbed, it is known as selective reabsorption.
          1138039_858551_ans_299bd0f0ab1f42108b2bd2c7d59f7d65.jpg


          Draw a labelled diagram of the sagittal section of the human kidney.


          1155264_858539_ans_2b53aa533e8b4b71a189d88a2d9d6464.jpg


          Value based questions.
          Imagine a water molecule has just entered the proximal convoluted tubule of the nephron
          that will eventually be part of the urine. What parts of the nephron will it travel through (in order) before it reaches the renal pelvis?

          The water molecule that enters PCT in nephron travels in the following order:

          Proximal convoluted tubule→→ descending limb of the loop of Henle→→  ascending limb of the loop of Henle→→ distal 
          convoluted tubule→→ collecting duct→→  papillary duct →→ minor calyx →→ major calyx →→renal pelvis.


          Differentiate between proximal and distal convoluted tubules. (Based on their position)

          Both proximal convoluted tubule and distal convoluted tubules are the parts of a renal tubule. The proximal convoluted tubule, arising from the Bowmans capsule, traverses within the cortex. The cells of this tubule are large and columnar and have brush borders in their apical surface. On the other hand, the distal convoluted tubule has a straight part continuous with the ascending limb of the loop of Henle and a convoluted part lying in the cortex.


          Which organs are associated with a major excretory system in mammals? Describe briefly the structure of a nephron.

          Kidneys are associated with the major excretory system in mammals. 
          The nephron is the functional unit of the kidney, with each nephron being comprised of the following components:
          • Bowman’s capsule – the first part of the nephron where blood is initially filtered (to form filtrate).
          • Proximal convoluted tubule – folded structure connected to the Bowman’s capsule where selective reabsorption occurs.
          • The loop of Henle – a selectively permeable loop that descends into the medulla and establishes a salt gradient.
          • Distal convoluted tubule – a folded structure connected to the loop of Henle where further selective reabsorption occurs
          • The blood to be filtered enters the Bowman’s capsule via an afferent arteriole and leaves the capsule via an efferent arteriole. Within the Bowman’s capsule, the blood is filtered at a capillary tuft called the glomerulus. 
          • The efferent arteriole forms a blood network called the vasa recta that reabsorbs components of the filtrate from the nephron.
          • Each nephron connects to a collecting duct (via the distal convoluted tubule), which feed into the renal pelvis.

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          Show the structure of a renal corpuscle with the help of a diagram.

          The following figure shows the structure of a renal corpuscle. It has following parts:
          Bowman's Capsule : This is a capsule - shaped structure. Filtrates from arteriole are collected in this and sent through the Proximal convoluted tubule.
          Afferent Arteriole : This arteriole brings blood to the glomerulus.
          Efferent Arteriole : This arteriole takes away blood from the glomerulus.
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          Short / Long answer type questions.
          What is feedback control? Illustrate feedback mechanism of homeostasis by an example of hormones.

          • The endocrine glands secrete hormones depending upon the need of the organism. The number of hormones secreted should be accurate. The regulation of the quantity of the hormones and the timing of its release are controlled by feedback mechanisms.
          • There are two types of feedback mechanisms - positive and negative feedback.
          1. Positive feedback: In this mechanism, the response accelerates after the feedback. The effect is further intensified in the same direction. It helps in speeding up the process occurring in various body systems. It is the opposite of negative feedback.
          2. Negative feedback: In this mechanism, the information given by the feedback causes a reverse response. It occurs when the system needs to slow down or completely stop a process.
          • For example Childbirth 
          Uterine contractions occur during the onset of labour pain. These contractions stimulate the release of a specific hormone called oxytocin (from the pituitary gland), which intensifies the contractions. The contractions further stimulate the production of oxytocin and this cycle stops only after the birth of the baby. This is an example of positive feedback.


          Give a brief account on human excretory system. Add a note on vertical section of kidney. 

          The excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to help maintain internal chemical homeostasis and prevent damage to the body. In humans, the excretory system consists of a pair of kidneys, one pair of ureters, a urinary bladder and a urethra.
          VS of the kidney: Each kidney of an adult human measures 10-12 cm in length, 5-7 cm in width, 2-3 cm in thickness with an average weight of 120- 170 g. Towards the centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter. Inner to the hilum is a broad funnel-shaped space called the renal pelvis with projections called calyces. The outer layer of the kidney is a tough capsule. Inside the kidney, there are two zones, an outer cortex and an inner medulla. The medulla is divided into a few conical masses (medullary pyramids) projecting into the calyces (sing.: calyx). The cortex extends in between the medullary pyramids as renal columns called Columns of Bertini.


          What is homeostasis?

          Explanation:
          • Homeostasis is a healthy state or stable condition, in which the internal environment of the body is maintained relatively constant despite any changes in the external environment.
          • It is the property of the cell, tissue, or organism that maintained the steady state by constant adjustment of biochemical and physiological pathways, necessary for the survival of an organism.
          • For optimal functioning, body temperature, fluid balance, blood pH, blood glucose levels, sodium, potassium, and calcium ion concentrations are regulated. 



          Name any two substances which are selectively reabsorbed from the tubules of a nephron.

          The nephron is the functional unit of the kidney. Some of the substances selectively reabsorbed from the tubules of a nephron are
          • Ions
          • Glucose
          • Amino acids 
          • Urea etc...


          What is the tube that passes urine to outside of the body?

          The urethra is the tube that carries urine from the bladder out of the body. The internal urethral sphincter prevents urine from leaving the bladder to enter the urethra. It is controlled by involuntary system. The external urethral sphincter is under voluntary control.


          How does the blood come out of the capillary and come in contact with the Bowman's capsule so as to form filtrate?

          • Bowman's capsule is also known as a glomerular capsule.
          • Its performs the first step in the filtration of blood to form urine.
          • The process of filtration of the blood in the Bowman's capsule is known as ultrafiltration.
          • The blood enters into the capsule by the afferent ateriole under high pressure.
          • The fluids from blood in the glomerulus are collected in the Bowman's capsule called the glomerulus filterate which is further processed along the nephron to form urine.
          • The filtration barrier is composed of the perforated endothelium of the glomerular capillaries.
          • This barrier permits the passage of water, ions and small molecules from the bloodstream into the Bowman's space.
          • The barrier prevents the passage of large and negatively charged proteins.


          Describe the process of ultrafilteration.

          The process of ultrafiltration occurs in the nephrons of the kidneys. The process can be described as follows:
          1. Blood flows through the glomerulus that is surrounded by the Bowman's capsule. The hydrostatic pressure forces the small molecules to leave the glomerulus and enter in the Bowman's capsule. Cells and proteins are not able to pass due to the large size.
          2. In Bowman's capsule, the plasma that has come from the glomerulus is called the filtrate.
          3. The filtrate moves to the proximal convoluted tubule where the process of reabsorption of solutes begins. Sodium, potassium, glucose, amino acids are absorbed in here, and water is also moved across the tubule.
          4. The filtrate passes on to the Loop of Henle. 


          Describe Malpighian body. Explain its role in urine formation.

          Malpighian body is made up of the glomerulus and the Bowman's Capsule. The glomerulus is a network of capillaries that receives blood from the afferent arteriole and gives it further to the efferent arteriole. From the glomerulus, the component of blood diffuse into the Bowman's Capsule through the endothelium and basement membrane of the glomerulus and the epithelium of Bowman's Capsule.
          The Bowman's Capsule receives the filtrate from the glomerulus. It is made up of a double layer called the parietal layer and the visceral membrane. The visceral membrane has special cells called the podocytes, that have spaces in between them through which the glomerular filtrate is filtered.
          The blood comes into the glomerulus through which it is diffused into the Bowman's capsule. Only the smaller solute molecules and water is allowed to pass through the membranes while the blood cells are retained within the glomerulus. Hence, the Malpighian Body allows the filtration of blood so that the waste can be separated from the blood. The filtrate further moves to tubules where fine reabsorption and secretion takes place. Both the kidneys produce approximately 180 liters of filtrate every day.


          Given is a jumbled list of the parts of a certain body structure - Loop of Henle, Bowman's capsule, convoluted tubule, glomerulus, proximal convoluted tubule.
          (i) Name the structure to which the listed parts belong.
          (ii) Rearrange the parts in their proper sequence from the starting point to where they end.

          (i) The structure to which the listed parts belong is the Kidney.
          (ii) Blood is filtered in the kidney under high pressure, a process called ultrafiltration.  Filtration is a way of separating a mixture of chemicals based on the size of the particles and this is exactly what happens to the blood in the kidney.  Red blood cells, white blood cells and platelets are all too large to cross the filtration barrier.  Blood plasma (with the exception of large plasma proteins) is filtered from the blood forming a liquid called glomerular filtrate.  The kidneys produce about 180 litres of glomerular filtrate per day. Ultrafiltration happens in the glomerulus and the glomerular filtrate (GF) passes into the Bowmans capsule.  The high pressure is generated by the blood vessel that takes blood into the glomerulus (afferent arteriole) being much wider than the blood vessel that takes blood out of the glomerulus (efferent arteriole).  The plasma of blood (minus the large plasma proteins) is squeezed out of the very leaky capillaries in the glomerulus and into the first part of the nephron.

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          Define excretion. Describe the structure of nephron. Write a note on the physiology of urine formation.

          Excretion can be defined as the process of removal of nitrogenous waste produced by the metabolic activity of the cells. In humans, urea is the major nitrogenous waste. Uric acid and creatinine are also expelled in the process of excretion.
          Nephrons are the structural and the functional units of kidneys. They perform the function of blood filtration, ionic absorption, and the formation of concentrated urine. A nephron is made up of two main parts as Malpighian Body and Renal Tubules. 
          Malpighian body is made of:
          1. Glomerulus: coiled capillaries through which blood enters for the filtration. 
          2. Bowman's capsule: the cup-like structure that encloses the glomerulus. Blood plasma is diffused into the Bowman's capsule from the glomerulus.
          Renal Tubules are made up of:
          1. Proximal Convoluted Tubule: it is situated close to the Bowman's Capsule and performs the absorption of water, electrolytes, glucose from the filtrate.
          2. The loop of Henle: it is a U-shaped tubule and has a descending limb and an ascending limb. It performs a role in counter-current mechanism.
          3. Distal Convoluted Tubule: it is the distal tubular portion which performs the absorption of electrolytes and also secretes the excessive electrolytes.
          Physiology of urine formation: It occurs in three steps as follows:
          1. Glomerular Filtration- the water, minerals, ions, and solutes are diffused out of the blood and move into the Bowman's capsule forming a filtrate.
          2. Tubular reabsorption: the necessary substances such as water, glucose, amino acids, vitamins, mineral ions in the filtrate are reabsorbed by the tubules of the nephrons. The loop of Henle regulates the water reabsorption.
          3. Tubular secretion: K$$^{+}$$, H$$^{+}$$, creatinine and excessive water are secreted out from the tubules into the filtrate. Such a filtrate is called the urine.


          Describe the human excretory system. Write a note on vertical section of kidney.

          Human excretory system is concerned with the removal of the metabolic waste produced in the cells and diffused into the blood. The excretory system is made up of the following parts: 
          1. Kidneys: A pair of kidneys located on each side of the vertebral column are the major organs that perform the filtration of the blood and produces urine. The nephrons are the coiled structure present in each kidney are the functional and structural units.
          2. Renal Artery: It brings the blood to be filtered to the kidneys.
          3. Renal vein: It carries the filtered blood away from the kidneys.
          4. Ureters: a pair of ureters, each attached to the individual kidney takes the urine from kidneys to the urinary bladder.
          5. Urinary bladder: it stores the urine and upon getting filled, it contracts and passes the urine to the urethra.
          6. Urethra: A tubular outlet through which urine goes out of the body.
          A vertical section of kidney shows the following structural details:
          1. Renal capsule; Outermost covering on the kidney, it is made up of collagen and elastin fibres. It protects kidneys from the injuries.
          2. Renal Cortex: In the kidney, the outer region is called cortex. It contains Malpighian Bodies of the nephrons.
          3. Renal Medulla: Inner region of the kidney is medulla. It is made up of 15-16 conical structures called Pyramids. The tubules of nephrons lie in the pyramids.
          4. Pelvis: It connects the pyramids with the ureter cavity and urine is passed to the ureter through the pelvis region.



          The blood vessel which-
          (a) Enters the malpighian corpuscles
          (b) Leaves the malpighian corpuscles

          (a) Afferent arteriole - The afferent arterioles are a group of blood vessels that supply the nephrons in many excretory systems. The afferent arterioles branch from the renal artery, which supplies blood to the kidneys. The afferent arterioles later diverge into the capillaries of the glomerulus.
          (b) Efferent arteriole - The efferent arterioles are blood vessels that are part of the urinary tract of organisms. Efferent (from Latin ex + Ferre) means "outgoing", in this case meaning carrying blood out away from the glomerulus. The efferent arterioles form from a convergence of the capillaries of the glomerulus and carry blood away from the glomerulus that has already been filtered. They play an important role in maintaining the glomerular filtration rate despite fluctuations in blood pressure.
          Malpighian body is constituted by


          Define excretion. Explain mechanism of urine formation.

          Excretion can be defined as the process of removal of nitrogenous waste produced by the metabolic activity of the cells. In humans, urea is the major nitrogenous waste. Uric acid and creatinine are also expelled in the process of excretion.
          Mechanism of urine formation: It occurs in three steps as follows:
          1. Glomerular Filtration- the water, minerals, ions, and solutes are diffused out of the blood and move into the Bowman's capsule forming a filtrate.
          2. Tubular reabsorption: the necessary substances such as water, glucose, amino acids, vitamins, mineral ions in the filtrate are reabsorbed by the tubules of the nephrons. The loop of Henle regulates the water reabsorption
          3. Tubular secretion: K$$^{+}$$, H$$^{+}$$, creatinine and excessive water are secreted out from the tubules into the filtrate. Such a filtrate is called the urine.


          The organs of excretion in arthropoda is __________

          Organs of excretion in arthropoda are malpighian tubules. They are slender tubes normally found in the posterior regions of alimentary canal at the junction of the midgut and hindgut.


          What is meant by excretion? Explain the process OR Describe the mechanism of urine formation. 

          Excretion is the removal of waste mainly urea with the help of urine by kidneys. Proteins are digested to form amino acids and the final by-product of the degradation of ammonia is urea. This urea containing blood (blood filtrate) is carried from the liver to the kidneys for its final excretion as urine. The formation of urine from blood filtrate is a complicated process involving thee major steps:
          1. Glomerular filtration: During this process fluid is filtered from the plasma into the Bowman's capsule at a rate of about 120ml/min. The process helps in the removal of blood cells and proteins from the filtrate. The resulting filtrate is called the ultrafiltrate.
          2. Tubular reabsorption and secretion: At various places in the proximal convulated tubule, loop of Henle, distal convulated tubule and collecting duct, sodium ions are reabsorbed actively from the filtrate into the blood vessels and chloride ions passively. During this process, water is also transported passively across the walls to maintain the osmotic balance. Substances such as potassium ions,  hydrogen ions, ammonia and toxic compounds such as dyes and drugs enter the filtrate by the process of secretion. This causes changes in the composition of the glomerular filtrate resulting finally in the formation of urine. 

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          Which part of Nephron  is not permeable for water ?
          1105348_087d26b5fc694cf99e1baa7e1e0a8578.png

          • The walls of the thick ascending limbs are impermeable to water.
          • The first part of the nephron is responsible for the water reabsorbtion is the proximal convulated tubule


          Mention the differences between egestion and excretion. 

          Difference Between Egestion And Excretion
          EgestionExcretion
          The process involves removing undigested waste products food from the body of the organism through the digestive systemThe process involves removing wastes from the cells of organisms through the excretory system
          Discharged materials are undigested food and other toxic substances leftover from digestionDischarged materials are metabolic wastes such as carbon dioxide or oxygen
          Egestion mainly happens through the anus or the mouth (in animals such as jellyfish)Excretion happens through the nose, skin and the urethra
          Only animals undergo egestionExcretion happens in both plants and animals


          Write the special characteristics/features of the human excretory system

          Example: Human excretory system
          The characteristics of the excretory system are :
          1. It is an organ system that purifies the blood and removed the waste materials from the body.
          2. Organs like kidney act as filters and remove out the toxins.
          3. The excretion is done mainly in the form of uric acid, urea, and large amounts of water.
          4. It maintains internal chemical homeostasis.
          5. It protects the body from damage from toxic materials.
          6. It is responsible for osmoregulation and maintenance of water and salt concentration in the body.

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          What happens to glucose which enters the nephron along with filterate during excretion in human beings? State two vital functions of kidney.

          The molecules of glucose are very small. Hence, when it enters the nephron along with the filtrate during excretion, it is passed into the nephron tubule along with urea. However, by tubular reabsorption, the glucose along with some water and other important ions are reabsorbed and are used by the body.
          Vital functions of kidneys include:
          1. They remove the waste products like urea and other salts from the body. 
          2. They help in maintaining homeostasis of the body by regulating the concentration and volume of body fluids like water.


          What will happen if their is no tubular reabsorption in the nephrons of kidneys?

          If there will be no tubular reabsorption in the nephrons of kidneys, the useful substances like minerals and excess water will be eliminated from the body along with the urine. Tubular reabsorption is a selective reabsorption that allows the important components to get absorbed back into capillaries for the body to use them further.


          Draw a neat and correct diagram of the of the human kidney and label it.


          1026523_1113565_ans_54a7bc7c69cf466a83d73ea4e42379f5.png


          Name the organ in man concerned with maintaining water balance in the body.

          • In man 'Kidneys' are concerned with maintaining water balance in the body this occurs in response to release of ADH or Vasopressin.


          What is meant by osmoregulation? How is it maintained in human body?

          Osmoregulation is the process by which an organism regulates the water balance in its body and maintains the homeostasis of the body. 
          Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus
          to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis. An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release to complete the feedback. ADH can also affect the kidney function by its constrictory effects on blood vessels. This causes an increase in blood pressure. An increase in blood pressure can increase the glomerular blood flow and thereby the GFR.
          The JGA plays a complex regulatory role. A fall in glomerular blood flow/glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release Aldosterone. Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR. This complex mechanism is generally known as the Renin-Angiotensin mechanism.

          1058344_1146893_ans_d354962f6dd947d4bfe2b32a5cf01616.jpg


          Which cell organelle detoxifies poisons and drugs in the liver of vertebrates?

          Smooth endoplasmic reticulum in liver cells of vertebrates helps in detoxifying poisons and drugs. It contains enzymes that catalyze a number of reactions that can make lipid-soluble drugs and metabolic wastes into water-soluble so that these can easily be expelled out from the body. To perform such processes SER increases or doubles its surface area so lots of detoxification can take place.


          Describe the structure and functioning of nephrons.

          • The nephron is the filtration unit of the kidney. 
          •  It consists of a tubule that is connected with collecting duct at one end and a cup-shaped structure at the other end. This cup-shaped structure is called ‘Bowman’s capsule’. Every Bowman’s capsule contains a cluster of capillaries, called ‘Glomerulus’, within the cup-shaped structure. The blood enters into Glomerulus through afferent arteriole of the renal artery and leaves it through the efferent arteriole. Together, the glomerulus and its surrounding Bowman's capsule are called a renal corpuscle. 
          • Blood enters the glomerulus through a small artery supplying the glomerulus with unfiltered blood called the afferent arteriole. Another vessel, a small artery carrying filtered blood away from the glomerulus, is called the efferent arteriole. These two arterioles play a key role in helping the glomeruli's capillaries perform the process of ultrafiltration.
          • Nephron starts from Bowman’s capsule and consists of the following parts: proximal convoluted tubule (in the renal cortex), the loop of Henle (in the renal medulla), and distal convoluted tubule (in the renal cortex).
          i) proximal convoluted tubules (PCT): it is a proximal part of renal tubules next to Bowman’s capsule. It is lined with microvilli. Maximum reabsorption of water, glucose, amino acids and electrolytes takes place here.
          • ii) The loop of Henle: It is U shaped middle portion of renal tubules. It is composed of ascending and descending loop. Ascending loop is thick-walled and impermeable to water while the descending loop is thin-walled and permeable to water. The countercurrent mechanism is a crucial role of the loop of Henle.
          iii) Distal convoluted tubules (DCT): It is the distal part of renal tubules that lead to collecting ducts. It is similar in structure and function with PCT.

          • Functioning of Nephron:-
          1. Filtration: Filtration of blood takes place in Bowman’s capsule from the capillaries of the glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.
          2. Re-absorption: As the filtrate flows along the nephrons, substances such as glucose, amino acids, salts, and water are selectively re-absorbed into the blood by capillaries surrounding the nephron tube the leadule.
          The amount of water re-absorbed depends on the need of the body and also on the amount of wastes to be excreted.
          3. Urine: The filtrate which remains after re-absorption is called urine. Urine contains dissolved nitrogenous waste, i.e. urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting duct to carry it to the ureter.

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          Differentiate protonephridia from metanephridia.

          Two different kinds of nephridia occur within the Bilateria, protonephridia closed up by a terminal cell and metanephridia opening into the coelomic cavity. Both initially filter and subsequently modify intercellular fluids. Whereas metanephridia are strictly correlated to a coelom, proto-nephridia occur in acoelomate as well as in coelomate organisms. Protonephridia of different bilaterian taxa correspond to each other in several structural features. 


          What is tubular secretion? Name the substances secreted through the renal tubules.

          Tubular secretion is the transfer of materials from peritubular capillaries to the renal tubular lumen; it is the opposite process of absorption. This secretion is caused mainly by active transport and passive diffusion. Renal secretion is different from reabsorption because it deals with filtering and cleaning substances from the blood, rather than retaining them. 
          The substances that are secreted into the tubular fluid for removal from the body include :
          • Potassium ions (K+)
          • Hydrogen ions (H+)
          • Ammonium ions (NH4+)
          • Creatinine
          • Urea. 


          Draw the structure of a nephron and label the following ; Glomerulus ,Bowman capsule, renal artery, collecting duct, 
          b) What happen to glucose that enters the nephron along with the filtrate

          (a) The structure of nephron is drawn above.
          (b) Glucose that is filtered during ultrafiltration is actively absorbed through the proximal convoluted tubule.


          1085211_1212866_ans_d806112412ef4d82bf474be3e7efcf07.jpg


          Give reasons for this sentence:
          Urine is formed from alkaline blood but it is acidic in nature.

          Blood has an alkaline pH of 7.35 to 7.45. As against this, urine is acidic as it removes excess hydrogen ions from the blood during filtration processes.


          Draw the structure of nephorons are also labelled

          The image above shows the labelled diagram of a nephron and its associated blood vessels.
          1156826_1214077_ans_ddff8e884d184fef89024cfcb5c1ed88.jpg


          What is malpighian body?

           The glomerulus is made up of a cluster of blood capillaries formed from afferent arteriole and efferent arteriole. Afferent arteriole carries the blood into the glomerulus and Efferent arteriole carries the blood away from the glomerulus.  Bowmen’s capsule is the cup-like structure that encloses the glomerulus. Bowmen's capsule and glomerulus are together called malpighian body or renal corpuscle. It is part of the structure of nephron. 

          1098214_1230999_ans_3085c1d8d8e74c4198275cffc1f72c8e.jpg


          Draw a labelled structure of nephron.

          Nephrons are the basic filtering units of kidneys. Each kidney possesses a large number of nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus, Bowman’s capsule, and a long renal tubule.
          1097915_1233799_ans_7aeec360349a4f2d84e4d82d1ef30621.jpg


          Draw the structure of a nephron and label glomerulus, Bowman's capsule, renal artery, collecting duct.
          b) What happen to glucose that enters the nephron along with the filtrate?

          b) Glucose present in the blood plasma enters the nephron during the filtration process and after passing through the glomerulus the filtrate enters the renal tubule.
          • Reabsorption occurs in the renal tubules where glucose and other nutrients, water etc diffuse out of the renal tubules and enter the surrounding capillaries
          • These reabsorbed substances such as glucose and other nutrients are sent back to the bloodstream.

          1074490_1212390_ans_af51f6f4c211489dbf3e7a655185ff67.jpg


          What is the unit of excretory system?

          Nephron is the basic structural and functional unit of the kidney. The main function is to regulate water and soluble substances by filtering the blood, reabsorbing what is needed and excreting the rest as urine.


          Where does the initial production of urine occurs?

          • The formation of urine is done in the kidney by the nephron. 
          • The glomerulus which is responsible for filtration of the substances from the blood thus sending pureblood, these substances are then reabsorbed in the nephron such that only waste and excess water is removed in the form of urine. 


          With the help of a well labelled diagram, describe the structure of nephron 

          Each nephron has a Bowman's capsule a proximal convoluted tubule a loop of Henle's dismal convoluted tubules that lead to collecting duct nephrons. ... Each nephron has a Bowman's capsule which is a cup-shaped structure that has a layer made of squamous epithelia. cells in the cavity of the Bowman's capsule.
          1120358_1250553_ans_5ca64293560342a7a138ea0d04e5321b.png


          Explain in your own words.
          How does excretion occur in human beings?

          The removal of waste products from the body is known as excretion. In the human body, kidneys, lungs and skin perform the function of excretion. Lungs remove carbon dioxide as waste. Skin helps in the removal of waste in the form of sweat. However, the major organ involved in excretion is the urinary system, which contains the kidneys to filter the blood and form urine. 
          In human beings, excretion is performed by the excretory system consisting of a pair of kidneys, a pair of ureters, a urinary bladder and urethra. 
          The urine is formed in kidneys and passes on to the urinary bladder via the ureters. The urinary bladder stores the urine until it is excreted through the urethra. 
          The kidney contains numerous filtration units called the nephrons. Nephron is the structural and functional unit of the kidney. The nephrons consist of a network of capillaries associated with a cup-shaped end of a tube in which the filtered urine is collected. When the blood passes through the tube, some substances such as glucose, amino acids, salts, and water are selectively reabsorbed. The final filtrate is collected in the collecting tubule and eventually enters the ureters. 
          The other organs which are involved in the excretory process include: 
          (i) Lungs: They remove $$CO_2$$ and water. About 18 L of carbon dioxide is eliminated per day with the help of lungs. 
          (ii) Liver: It excretes bile pigments (such as bilirubin, biliverdin), vitamins, cholesterols and drugs along with digestive wastes. 
          (iii) Skin: Sweat and sebaceous glands present on the skin eliminate substances such as sterols, hydrocarbons,  sebum, etc. 
          1779008_1408482_ans_1bcd94dc736b4a20890f8af5fcf5fd53.png


          What is the role of fluid filtered out in Bowman's capsule?

          Fluids from blood in the glomerulus are collected in the Bowman's capsule (i.e., glomerular filtrate) and further processed along the nephron to form urine. This process is known as ultrafiltration. The main function of Bowman's capsule and glomerulus is carrying out the process of ultrafiltration.


          Mention the functions of 

          (a) Proximal convoluted tubule
          (b) Henle's loop
          (c) Distal convoluted tubule

          Nephron- It is the basic unit structure of kidney. It contains a tubule which is connected to collecting duct at one end and Bowman's capsule on the other. It helps in filtration, re-absorption, collecting of urine.

          Glomerulus- It is a ball like structure made up of capillaries and Bowman's' capsule surrounds it. It consists of endothelial cells, glomerular basement membrane, and Epithelial calls. It helps in urine filtration.

          Bowman's capsule- It is a capsule structure. it has single layer of epithelial cells. It receives the products of glomerular filtration which is known as ultrafiltration.

          Proximal convoluted Tubule- It is present in the kidney's codex. It is the site of re-absorption of ions and water. it reabsorbs the ultrafilter.

          Loop of Henle- It is a long duct and present in medullas part of the kidney. It as three-part thin descending limb, ascending loop, thick ascending limb. It collects the remaining of water to create concentration.

          Distal convoluted Tubule- It present in the cortex of kidney. It regulates pH of urine, reabsorb calcium, sodium and chloride.


          What is glomerulus? What role does it plays during urine formation?

          The main function of glomerulus is to filter plasma to produce glomerulus filtrate, which passes down the length of the nephron tubule to form urine.


          Briefly describe the structure and functions of nephron with neat labelled diagram.

          As we know that kidneys are the main excretory organ in human beings. They consists of basic structural unit called nephrons. There are about 1 million nephrons present in one kidney. All the nephrons are kept together by connecting tissue.

           

          The basic structure of nephrons consists of four parts.

          Glomerulus

          Bowman’s capsule

          Proximal Convoluted Tubule (PCT)

          Loop of Henle

          Distal Convoluted Tubule (DCT)

           

           

          Glomerulus is a tuft of blood capillaries that arise from afferent arteriole. The capillaries join again later to form efferent arteriole.  These arteriols take the blood to the nephron and supply back to body after filtration.

           

          Bowmans capsule is a cup like structure that holds glomerulus. It collects the filterate from the glomerulus and transforms into Proximal convoluted tubule.

           

          Proximal convoluted tubule is lined by columnar epithilaial cells. Columnar epithelial cells have various microvilli that increase the surface area to absorb the essential substances back into the blood.

           

          PCT leads to a U shaped structure called Loop of Henle. It consists of ascending and descending parts. That are lined with flat and columnar epithelial cells. They act to absorb water and concentration of urine.

           

          Distal Convoluted Tubule (DCT) continues from the ascending part of loop of Henle. This leads to Collecting duct. It is a very large duct that receive the filtration from various nepharons.

           

          The collecting ducts open into urethra and helps to take urine to urinary bladder where it is kept till elimination.


           Image result for Briefly describe the structure and functions of nephron with neat labelled diagram



          What causes the liquid part of blood to filter out from the glomerulus into the renal tubule?

          The glomerulus filters the blood.
          In the glomerulus, the diameter of the atriole is reduced. This causes an increase in the pressure of blood. Due to high pressure, the nitrogenous wastes and the water comes out and falls into the Bowman's capsule through the pores present in glomerulus.


          Explain about composition of urine?

          Urine is a sterile waste product made up of water soluble products made from nitrogen.The kidneys secrete urine, a typically sterile liquid by-product of the body, through a mechanism called urination and excreted through the urethra. Urine is often used for many disease circumstances as a diagnostic function. These may b based on either physical or chemical components, that may give insight to processes within the body, often through urinalysis, a common clinical analysis of urine. Normal urine consists of water, urea, salts, and pigments.Urea is a non-toxic molecule made of carbon dioxide and toxic ammonia. Any abnormal urinary constituents are an indication of illness.Urine is an aqueous solution of greater than 95% water, with a minimum of these remaining constituents, in order of decreasing concentration:

          Urea 9.3 g/L.
          Chloride 1.87 g/L.
          Sodium 1.17 g/L.
          Potassium 0.750 g/L.
          Creatinine 0.670 g/L.
          Other dissolved ions, inorganic and organic compounds (proteins, hormones, metabolites).


          Explain excretion in human beings.

          The wastes that are produced in human body are removed by the process of excretion. Human body consists of a number of excretory organs such as liver, skin, kidneys etc. But there is a specialized system in humans that helps to purifies blood. That is called excretory system. It consists of Kidneys, ureters, urethra, urinary bladder .

          Kidneys are placed in lower abdomen and bean like shaped. They filter the blood and removes toxins from the blood. It also reabsorbs the essential ions and substances from the filtrate. The final toxins are collected and removed from the body in the from of urine.

          The urine is 95% of water in composition and rest it contains urea and other wastes. 

          Image result for explain excretion in human beings




          Draw a labelled diagram of nephron.


          1310703_1517366_ans_1cb2ee34f3314a46bbce213f98984093.jpeg


          What is mainly digested by stomach of man?

          The digestion of proteins occurs in the stomach. It is facilitated by digestive enzymes (pepsin, hydrochloric acid). 


          Read the following table and answer the following questions.
          Sl. No.StructureLocation
          1.Tricuspid valveRight auriculo-ventricular aperture
          2.Guard cellsEpidermis of leaves
          3.Glomerulus Nephron
          4. AlveoliLungs
          5.Acrosome Above the head of a sperm
          Name the part performing Excretion. 

          Part performing excretion is Glomerulus.
          The main function of the kidney is the excretion of body wastes and harmful chemicals into the urine. Each kidney contains about one million nephrons. The nephron has three primary regions that function in the renal excretion process: the glomerulus, proximal tubule, and the distal tubule. Filtration takes place in the glomerulus, which is the vascular beginning of the nephron.


          Draw and label the diagram.
          Nephron


          1779718_1827507_ans_1d7da86e732f44d5bdce181910a20dcb.png


          Unscramble the given words below to get the correct word using the clues given against them.
          RETECOXNI: Waste products are removed by this process 

          RETECOXNI: Uscrambles as - Excretion : Waste products are removed by this process 


          Name the process and the organ which helps in removing the following wastes from the body.
          a) Carbon dioxide
          b) Undigested food
          c) Urine
          d) Sweat 

          WasteProcess     Organ
          Carbon dioxideExhalation     Lungs
          Undigested food     Egestion      Anus and large intestine
          Urine Excretion         Kidney 
          Sweat Sweating      Sweat glands


           Explain the structure of kidney. 

          Kidney resembles like kidney beans and is dark brown in colour. It is protected by a double layered capsule. There is a constriction In the middle and it is called hilum. There is a funnel shaped pelvis on the inner side of hilum. The outer part of kidney is called cortex and the inner part is called medulla. Each kidney has numerous filtering units called nephrons. 
          1759535_1835408_ans_0d563cae80314eb0964acd4cd88c6c5c.png


          Arrange the terms in correct sequence:
          Glomerulus, renal vein. efferent arterioles, renal artery, afferent arterioles, secondary capillaries.

          The correct sequence is as follows:
          Afferent arteriole, Glomerulus, Efferent arteriole. Renal artery. Secondary capillaries, Renal vein.


          Explain the internal structure of the kidney?

          The internal structure of the kidney: Kidney is divided into two parts. The outer part is called cortex and the inner part is called medulla. 
          (a) Nephrons: In medulla of each kidney, there are about one million coiled tiny tubules called nephrons. These are structural and functional units of the kidney. Each nephron is differentiated into two parts. Anterior part is called Malpighian capsule and remaining part is called tubule. 
          The outer part of Malphigian capsule is a cup-shaped structure called Bowman's capsule and a knot like  mass of blood capillaries situated in it, is called glomerulus. The capsule leads into a tubule. The beginning part is called proximal convoluted part. 
          There is a U shaped thin loop of Henle, which is followed by the distal convoluted part. It opens into the main collecting tubule. It finally opens into funnel shaped pelvis of the kidney. 

          (b) Ureter: A thin and muscular tube arises from each kidney. It is called ureter. It opens into the urinary bladder, by an opening. Both these ureters open into the urinary bladder. They bring urine from kidneys. 

          (c) Urinary bladder: It is a muscular bag in which urine is stored. It stores urine, temporarily. 

          (d) Urethra: It is a membranous tube, arising from the neck of the urinary bladder. By the contraction of muscles of the urinary bladder, the urine is passed out of the body through the urethra. 
          2035381_1834800_ans_77e6bc8bd3aa4141b9e8d54eafb3dfb3.png


          Label the different components of actin filament in the diagram given below.
          1848003_a4c18aaba8ef4aadbdeb35630aca92d4.png


          2037512_1848003_ans_f61077a5f24c4bc692e4058dfeb7126e.png


          Describe the structure and functioning of nephrons. 

          Structure of nephrons: It consists of a Bowman's capsule in which glomerulus is present (cluster of capillaries). The afferent artery brings the impure blood to nephron. The cup shaped structure (Bowman's capsule) form a tubular part of nephron which leads to collecting duct. 
          Working of Nephron 
          1. Filtration: The  afferent arteriole is wider and slowly it becomes a narrow tube in the glomerulus. Due to difference in the ‘width. a difference iin pressure is caused and water with dissolved impurities are squeezed out from the tube. It is collected in the Bowman's capsule which is cup-like structure and passes into the tube. 
          2. Reabsorption: The above filtrate passes through the tubule where the major amount of water, glucose. amino acids are selectively reabsorbed by the capillaries which are surrounding the tubule. 
          3. Urine formation: The water and impurities which are not reabsorbed is sent to a collecting duct. This filtrate contains more of dissolved nitrogenous wastes i.e. urea and hence it is termed as urine. From here the urine enters the ureter and is collected in urinary bladder..
          1764409_1836908_ans_31647806bd3c4aef9a5edc1002dfb6a3.jpeg


           Explain the structure of a nephron. 

           A nephron is composed of the filtering unit and highly convoluted ducts. The filtering unit is called glomerular apparatus. It is composed of a cup-shaped structure called Bowman's capsule. There is a tuft of capillaries inside Bowman's capsule. This tuft of capillaries is called glomerulus. It filters blood, the filtrate is collected in the Bowman's capsule. The filtrate containing a large amount of water with various dissolved substances and wastes moves through the Proximal convoluted tubule, the loop of Henle, the distal convoluted tubule and finally the collecting duct, that contains the formed urine. 
          During its movement through the tube about 90% of the water is reabsorbed, certain useful ions and compounds are reabsorbed while ions of certain salts are released into this solution through tubular secretion by Distal convoluted tubule which then is the composition of urine.


          Name two actively transported substances in Glomerular filtrate.

          Glucose, Amino acids are two actively transported substances from the glomerular filtrate.


          Which is the functional unit of kidney? 

          Answer:
          The kidneys are powerful chemical factories that perform the following functions: remove waste products from the body. remove drugs from the body. balance the body's fluids. release hormones that regulate blood pressure
          The structural and functional units of kidneys are nephrons. A nephron is a microscopic unit of a kidney that facilitates waste removal from the blood. A nephron consists of two parts mainly – renal tubule and renal corpuscle.



          Explain the organs involved in excretion, other than kidney. 

          Other organs involved in excretion are as follows: 
          Lungs: Carbon dioxide is removed through lungs. 
          Skin: Some excretory products are removed from skin along with sweat. 
          Mouth: Some waste products are removed from mouth along with spit.


          Explain why the composition of glomerular filtrate is not the same as urine.

          When the volume of the filtrate is compared with that of the urine that is formed per day, which is 180 litres and 1.5. Litres respectively, most of the filtrate needs to be reabsorbed by the renal tubules, the phenomenon is referred to as reabsorption. Substances such as amino acids, Na+, glucose are actively reabsorbed in the filtrate hence, are not found in urine.


          What is Ultrafiltration? 

          The process of filtration of blood from the glomerulus into the Bowman's capsule because of increased glomerular blood pressure is called as Ultrafiltration. 


          What is the main role of kidneys in the body? 

          Removal of nitrogenous waste product (urea) from the body is the principal role of the kidney.


          Name the organs that form the excretory system in human beings.

          The organs that form the excretory system in human beings are: -
          Kidneys, Ureters, Urinary bladder, Urethra, Liver, Skin, Lungs and Large intestine.


          Write the name of the excretory unit in the kidney.

          Nephron or uriniferous tubule is the excretory unit in the kidney.


          The glomerular filtrate in the loop of Henle gets concentrated in the descending and then gets diluted in the ascending limbs. Explain.

          The descending limb of Henle's loop is more permeable to water and almost impremeable to electrolytes. As a result, filtrate gets concentrated as it moves down the descending limb of Henle's loop.
          The ascending limb of Henle's loop is impermeable to water but permeable to electrolytes. As a result, the filtrate gets diluted as it moves up the ascending limb of Henle's loop.


          What is the malpighian body?

          The anterior part of the nephron is called a Malpighian body. It includes glomerulus and Bowman's capsule. 


          Label the parts marked 2 andMention the function of part 5.

          The parts labelled are as follows;
          2 - Left Ureters
          4 - Sphincter muscle
          5 - Urine is expelled from urinary bladder through urethra. 


          Name the following:
          (a) A chordate animal having flame cells as excretory structures.
          (b) Cortical portions projecting between the medullary pyramids in the human kidney.
          (c) A loop of capillary running parallel to the Henle's loop.

          (a) Flame cell is a type of excretory and osmoregulatory system. Examples of chordate animal having flame cells as excretory structures are Amphioxus, Flatworms, etc.
          (b) The cortical portions projecting between the medullary pyramids in the human kidney are the columns of Bertini. They represent the cortical tissues present within the medulla.
          (c)  A loop of capillary that runs parallel to Henle’s loop is known as vasa rectae. Vasa rectae, along with Henle’s loop, maintain a concentration gradient in the medullary interstitium.


          Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

          $$\textbf{Solution:}$$

                     Alveoli                   Nephrons

          $$\bullet$$ air sacs present in the lungs facilitate the exchange of gases. 

          		$$\bullet$$ Filtration units of kidneys that filter blood and forms urine.
          $$\bullet$$ They belong to the respiratory system. 
          		$$\bullet$$ They are a part of the excretory system.
          $$\bullet$$ They are made of simple squamous epithelium. 
          		$$\bullet$$ They are made of simple cuboidal epithelium.
          $$\bullet$$ They are surrounded by blood vessels.$$\bullet$$ They are surrounded by blood vessels as well as made up of blood vessels (Glomerulus part).
          $$\bullet$$ Around 350 million alveoli are found in each lung.
          		$$\bullet$$  Approximately 1.5 million nephrons are present in each kidney.



          Explain the Human Excretory System with the help of suitable diagram.

          Human excretory system:
          (a) In humans, the excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra.
          (b) Kidneys are two bean shaped organs lying at the back of the abdomen, one on either side of the vertebral column. Waste products from the blood and urine are removed by the kidney.
          (c) A Nephron is the basic filtration unit of the kidney. It is a cluster of thin walled blood capillaries.
          (d) The urine produced by filtering the blood is transported to the urinary bladder. This is done by a pair of ureters. Ureters are long muscular tubes.
          (e) Urinary bladder is a muscular bag like structure which can hold urine. The urinary bladder is under the control of nerves. When the bladder is full one get urge to urinate.
          (f) This urine is thrown out of the body through urethra.
          (g) Apart from the kidney, the skin and lungs are also helpful in the excretion.

          625079_592572_ans.png


          Mention the exact location of the following structures:
          $$(i)$$ Thylakoids
          $$(ii)$$ Organ of Corti
          $$(iii)$$ Lenticels
          $$(iv)$$ Bicuspid valve
          $$(v)$$ Loop of Henle

          (i) In the grana of the chloroplast; Thylakoids are the third membrane system of chloroplasts and contain photosystems.
          (ii) Organ of corti is located in middle cochlear canal in the inner ear and has hair cells (mechanoreceptors) on its basilar membrane. 
          (iii) On older stem; Lenticels are the aerating pores formed by rupture of the epidermis of root and stem at several places after secondary growth 
          (iv) Between the left auricle and left ventricle; bicuspid (mitral) valve has two cusps.
          (v) In renal medulla; Loop of Henle is the “U” shaped region of the nephron and serves to establish an osmotic gradient in the renal medulla. 


          Differentiate between the following pairs on the basis of what is mentioned in brackets :
          (i) Photolysis and Photophosphorylation. (Definition)
          (ii) Bicuspid valve and Tricuspid valve. (Function)
          (iii) Vasectomy and Tubectomy. (Explain)
          (iv) Cerebrum and Spinal cord. (Arrangement of nerve cells)
          (v) Bowman's capsule and Malpighian capsule. (Parts included)

          (i) Photolysis: Splitting of water in the presence of sunlight by activated photosynthetic pigments.
          Phosphorylation: Formation of ATP from ADP and inorganic phosphate by the utilization of energy released by electrons emitted due to photolysis of water.
          (ii) Bicuspid Valve: It closes the opening of auriculo-ventricular valves when blood rushes from left auricle into the left ventricle.
          Tricuspid Valve: It closes the opening of auriculo-ventricular valves when blood rushes from right atrium to right ventricle.
          (iii) Vasectomy: (a) Sterilization strategy in males.
                                    (b) Surgical cutting of vasa deferens of the males and ligation of cut ends for control of fertility.
          Tubectomy: (a) Sterilization strategy in females.
                               (b) Surgical cutting of fallopian tubes of a woman and ligation of cut ends to control fertility.
          (iv) Cerebrum: Grey matter is found on the outer side contains cell bodies of the neurons whereas white matter remains towards the inner side which mainly contains the axons (nerve fibre) of the neuron.
          Spinal Cord: White matter lies towards the outer side contains the cell body of the motor (efferent and association neuron) while the grey matter remains towards inner side contains axons.
          (v) Bowman's Capsule: It is a cup-shaped structure which indicates beginning of nephron, made up of two layers outer and inner.
          Malpighian Capsule: It comprises glomerulus and Bowman's capsule.


          The diagram given shows a section of a human kidney. Study the diagram carefully and answer the questions that follow:
          $$(i)$$ Label the parts numbered $$1$$ to $$4$$.
          $$(ii)$$ Why does part '$$2$$' have striped appearance?
          $$(iii)$$ What is the fluid that passes down part '$$4$$'? Name the main nitrogenous waste present in it.
          $$(iv)$$ Mention the structural and functional units of kidneys.
          $$(v)$$ Name the two major steps in the formation of the fluid mentioned in $$(iii)$$.
          577459.PNG

          (i)  1. Cortex; 2. Medulla; 3. Pelvis; 4. Ureter.
          (ii) The medulla consists of several medullary which are striped in appearance because they contain microscopic coiled tubes called nephrons.
          (iii Fluid that passes down from the renal pelvis to the ureter is urine formed by millions of nephrons. The main nitrogenous waste present in the urine is urea.
          (iv) The nephron is the structural and functional unit. 
          (v) 1. Ultrafiltration 2. Selective Readsorption.


          Sketch a labelled L. S. of human kidney.


          625414_601647_ans_a2760840f03f479088bf7b22c792b96d.png


          Which is the basic filtration unit in the human excretory system?

          Nephron is a cluster of thin walled blood capillaries is the basic filtration unit of the human excretory system. In humans, a normal kidney contains 800,000 to 1.5 million nephrons. The nephron carries out all the functions of kidney and known as the functional unit of a kidney. It helps in filtration of blood from toxic materials.


          The Master chemists of our body are the kidneys. Justify.
          (i) Kidneys filter all chemicals in the body.
          (ii) Kidneys maintain the chemical composition of blood.
          (iii) Kidneys eliminate all chemicals absorbed by the body.
          (iv) Kidneys store the chemicals accumulated in the body.

          i ) The main fluid filtered by the kidney is blood. It filters out all the waste and extra fluid from the blood. So, kidneys don’t filter all the chemicals in the body. So, (i) Statement is false.
          ii) The kidneys play a vital role in keeping the blood composition balanced. They filter the excess water and waste products, which are secreted from the kidneys in the form of urine. So, (ii) statement is correct.
          iii) kidneys eliminate the materials or products which are not required by the body like the urea and the creatinine and also eliminates the substances which are in excess. The useful substances like glucose, fats are not eliminated by the kidneys. So, (iii) statement is false.
          iv) Normally, there is no accumulation of any substances in the kidney, it’s function is to filter the fluids. So, (iv) statement is false.


          Sketch and label structure of nephron.

          Structure of Nephron
          626655_602372_ans_e50f2d6b865440d481b4e017135d0dc5.png


          Describe the excretory system of man giving the structure of a nephron.

          Answer:

          • In humans, the excretory system consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra. 
          • A nephron is the basic filtration unit of the kidney.
          • It is a cluster of thin-walled blood capillaries. 
          • There are different parts of the nephron in which the formation of urine take place. 
          • Bowman's capsule and the glomerulus are together called the glomerular apparatus.
          • There are afferent and efferent arterioles that bring and carry the blood away. 
          • The blood is filtered by the glomerulus and enters the Bowman's capsule where the podocytes help in the filtration and the glomerular filtrate is formed. 
          • When the glomerular filtrate comes to the proximal tubule then the essential nutrients are reabsorbed.
          • There are two limbs of the loop of Henle, ascending and descending limbs. 
          • The countercurrent exchange mechanism occurs which help in the regulation of the water and ions in the blood. 
          • When the glomerular filtrate is in the proximal tubule creatinine, uric acid is secreted in it.
          • When the filtrate goes to the distal part urea, potassium ion and some hydrogen ions are secreted in it. 
          • The urine which is formed is transported by the collecting tubules to the renal pelvis.
          • The urine is transported out by the ureters to the urinary bladder to store and excrete the urine from the urethra.

          2145815_609594_ans_6fbc65b11f45445ba17bba6390ce516a.JPG


          Match column I with column II regarding human excretory system. Choose the correct option.

          A. Podocytes are the epithelial cells that line the Bowman's capsule. They have slit like pores between the cells and they help in filtration of blood and allows the excessive and waste materials from the blood to pass into the Bowman's capsule.
          B. The columns of extension of cortex in between the renal pyramids are called Columns of Bertini. Each column consists of lines of blood vessels, urinary tubes and a fibrous material.
          C. A Juxta medullary nephron is a type of nephron in which the glomerulus, PCT, DCT lie in the cortex bu the Loop of Henley is long and extends into inner medulla. Cortical nephrons have short Loop of Henley and they extend only upto outer zone of medulla.
          D. Vasa recta are a group of blood vessels that runs parallel to the Henle's loop and help in counter current mehanism.
          E. The juxtaglomerular apparatus is a specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole. Its main function is to regulate blood pressure and the filtration rate of the glomerulus.


          Study the diagram given alongside and then answer the questions that follow:
          Name the region in the kidney where the above structure is present?
          label the parts 1, 2, 3,4.

          843935_da5ba17f48114ca1983ea5ec562f06bb.JPG

          The above given diagram is the Bowman's capsule, which is a cup-like sack at the beginning of the tubular component of a nephron in the mammalian kidney.
          The labelled parts as given below:
          1: Afferent arteriole
          2: Glomerulus
          3: Bowman's capsule
          4: Efferent arteriole



          Short / Long answer type questions .
          What do you understand by Homeostasis ? Write the name of scientist who used this word for the first time.

          Homeostasis is the ability to maintain a constant internal environment in response to environmental changes. The concept of the regulation of the internal environment was described by French physiologist Claude Bernard in 1865, and the word homeostasis was coined by Walter Bradford Cannon in 1926.


          Write short notes on the renal threshold.

          The renal threshold is the concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine. When the renal threshold of a substance is exceeded, reabsorption of the substance by the proximal convoluted tubule is incomplete. Hence, part of the substance remains in the urine.
          The renal threshold varies with the substance and it is altered with different disorders. For example, the most common reason for the glucose renal threshold to exceed is diabetes.


          What are the factors that favour glomerular filtration ?

          Glomerular filtration occurs due to the pressure gradient in the glomerulus.
          The factors that favour glomerular filtration are : 
          1. Increased blood volume and increased blood pressure.
          2.Dilation of afferent arterioles going to glomerulus and constriction of efferent arterioles coming out of glomerulus.
          3. Low hydrostatic pressure in Bowman's capsule. 


          Describe the role of liver, lungs and skin in excretion.

          Role of liver in excretion : Liver is the largest gland in vertebrates. Liver changes the decomposed haemoglobin of the worn out red blood corpuscles into bile pigments bilirubin and biliverdin. It helps in detoxification of toxic chemicals and drugs. It excretes cholestrol, steroid hormones, drug metabolites and other waste materials produced in the body through bile. Urea produced in the liver (by urea cycle) is one of the major excretory product of humans.
          Role of lungs in excretion : Lungs are the respiratory organs situated in the thorax. They help in filtration of air and excretion of carbon dioxide. It also helps in excretion of volatile drugs and alcohol metabolites during expiration.
          Role of skin in excretion : Skin is the largest organ in the body that also helps in excretion through sweat glands and sebaceous glands. Sweat glands help in excretion of excess water, salts, uric acid and drug metabolites. Sebaceous glands secrete an oily secretion called sebum. 


          Given below are five groups of five terms in each. Arrange the terms in each group in their proper sequence.
           I.Renal Pelvis, Urethra, Ureter Kidney Urinary Bladder
          ii. Sodium ions move into the axon, Repolarisation. Polarisation, Stimulus, Depolarisation
          iii. ATP is produced, guard cells photosynthesise during the day guard cells become more turgid. guard cells become hypertonic, Potassium ions are actively pumped into the guard cells
          iv Efferent ducts, Network of ducts, Seminiferous tubules. Urethra, Vas deferens v. Response, Effector Brain or Spinal Cord, Receptor Stimulus

          I. Kidney, Renal Pelvis, ureter, urinary bladder, urethra.
          II. Polarisation, stimulus, Sodium ions move into axon, depolarisation, repolarization.
          III. ATP is produced, potassium ions are actively pumped into the guard cells, guard cells become hypertonic, guard cells become more turgid, guard cells photosynthesize during the day.
          IV. Seminiferous tubules, efferent ducts, the network of ducts, vas deferens, urethra.
          V. Stimulus, receptor, brain or spinal cord, effector, response.


          Mention any two substances which are selectively reabsorbed as the filtrate flows along the tubular paths of this unit.

          $$\textbf{Solution:}$$

          $$\bullet$$ Multiple substances are selectively reabsorbed from the filtrate that enters the nephron through Bowman's capsule. 

          $$\bullet$$ Most of the reabsorption takes place in the proximal convoluted tubule.

          Two substances that are selectively reabsorbed from the filtrate are $$\textbf{amino acids}$$ and $$\textbf{glucose}$$. 

          $$\bullet$$ Amino acids and glucose are both essential components of the body which is why it needs to be brought back to the blood plasma. 

          $$\bullet$$ From the tubule of the nephron, the glucose and amino acids again enter the system so that they can be metabolized and used for the production of energy. 



          Which of Maya's organs is not working properly? (brain/heart/kidneys)

          Kidney:
          The kidneys are two bean-shaped organs whose major functions are to remove waste products and excess fluid from the body and to produce hormones that regulate blood pressure, RBCs and other necessary substances.
          Kidneys play an important role in regulation of the body salt, potassium and acid content. The excess of waste products and fluids are removed in the form of urine excreted from the body.


          Cup shaped structure of renal tubule where ultrafiltration occurs.


          1339634_1471197_ans_2f6caf1dbb5543bf929aed91eb021cbe.png


          Given is an example of a certain structure and its special functional activity.
          "Kidney and excretion."

          Kidneys are bean shaped, reddish brown coloured with a tough fibrous connective tissue covering called renal capsule. The main function  of kidneys is excretion. The process of excretion or urine formation takes place in three steps:
          i) Ultrafiltration
          ii) Selective tubular reabsorption
          iii) Tubular secretion




          What is the location of kidneys in the body?


          1331858_1464771_ans_15fb1672213e40db9c8f6ab8e0a8f4af.jpg


          Describe the structure and functioning of nephrons.

          A nephron is the filtration unit of the kidney. It consists of a tubule which is connected with collecting duct at one end and a cup-shaped structure at the other end. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.
          1336201_1532614_ans_69f4da8a590f4243b25059dd1363bd23.jpg


          Name the structure help in excretion and osmoregulation in Earthworm and Cockroach.

          IN EARTHWORMS : Nephridia. 
          these structures help in excreting CO2 and nitrogenous wastes.
           they're two types of nephridia
          1. septal nephridia (present in the septa) and 
          2. integumentary nephridia (present in skin).
          In COCKROACH-
          The Malpighian tubule system is a type of excretory and osmoregulatory system found cockroaches. 


          What is the function of the kidneys in excretion? Explain with the help of a diagram.

          It is the responsibility of the urinary system to create urine and excrete or remove waste material from the body. Kidneys, ureters, and urethra are important organs of the urinary system. In the integumentary system, waste is also removed from the body through sweat glands and through the digestive and excretory systems. The primary route through the kidneys in which the body eliminates drugs. The kidney's primary role is the excretion into the urine of body waste and damaging chemicals. The nephron is the kidney's functional unit responsible for excretion. There are about one million nephrons in each kidney. In the renal excretion phase, the nephron has three main areas: the glomerulus, the proximal tubule, and the distal tubule. Three processes are involved in urinary excretion: Filtration, Secretion, Reabsorption.

          1328188_1495836_ans_17305862bd304cf89944d464b111b802.png


          A. List the three major steps involved in the formation of urine.
          B. Name the excretory unit of a kidney.
          C. State the two functions of the human kidney.
          D. What is the composition of urine?

          $$\textbf{A)}$$
          $$\textbf{Solution:}$$
          $$\bullet$$ The three major steps in the formation of urine are:
          $$\bullet$$ Glomerular filtration - Blood is filtered in the glomerulus and filtrate is formed.
          $$\bullet$$ Tubular reabsorption- When the glomerular filtrate comes to the tubule part of the nephron, the essential components like glucose, ions, water, etc. are reabsorbed.
          $$\bullet$$ Tubular secretion - Various secretions like creatinine, uric acid, etc are secreted in it to form urine.

          $$\textbf{B)}$$
          $$\textbf{Solution:}$$ Nephron

          $$\textbf{Explanation:}$$
          $$\bullet$$ Nephron is the excretory unit of a kidney.
          $$\bullet$$ There are millions of nephrons in each kidney.
          $$\bullet$$ They filter the blood and form urine.

          $$\textbf{C)}$$
          $$\textbf{Solution:}$$
          $$\bullet$$ Functions of kidneys:
          $$\bullet$$ Kidneys have small filtering units called nephrons that filter the blood and remove toxic wastes from it to produce urine.
          $$\bullet$$ Kidneys also help in regulating the water level of the body; for example, if the body needs more water, the urine is concentrated and water is reabsorbed in the tubule part.

          $$\textbf{D)}$$
          $$\textbf{Solution:}$$
          $$\bullet$$ Urine contains following components:
          $$\bullet$$ Mainly water
          $$\bullet$$ Urea
          $$\bullet$$ Inorganic salts
          $$\bullet$$ Some hormones, etc.



          Class 11 Medical Biology Extra Questions