CBSE Questions for Class 11 Medical Biology Breathing And Exchange Of Gases Quiz 14 - MCQExams.com

• Inspiration leads to an increase in the volume of the lungs, which is caused due to contraction of the diaphragm. 
• The intercostal muscles lift the ribcage. During inspiration, air flows into the alveoli because atmospheric pressure is greater than alveolar pressure. 
• Increasing thoracic volume results in decreased pleural pressure, increased alveolar volume, and decreased alveolar pressure. 
• Thus, air moves into the lungs.

• The nasal septum is the thin wall of bone and cartilage that separates the right and left nostrils.
• The bones comprising the nasal septum include the maxillary crest, vomer and the perpendicular plate of the ethmoid.
• Vomer bone is thin and quadrilateral in shape.
• The vomer forms the inferior part of the nasal septum and the superior part is formed by the perpendicular plate of the ethmoid bone.
• Hence the bone which forms the inferior part of the nasal septum is vomer.
• So, the correct answer is option B. 

$$\textbf{Correct option:C}$$ 

$$\textbf{Solution:}$$

$$\textbf{Option (A)}$$

$$\bullet$$ When the trachea bifurcates into a pair of primary bronchi which are supported by cartilaginous rings ,these branched enters each lungs and divides further to give rise to various bronchioles and bronchi.

$$\textbf{Option (B)}$$

$$\bullet$$ Alveoli are tiny air sacs in the lungs  that take up the oxygen you breathe in and keep your body going.

$$\textbf{Option (C)}$$

$$\bullet$$ Bronchioles are the subdivision of tertiary bronchi which are also without cartilagnous rings, the bronchioles are numerous and its diameter keeps on decreasing and made of thinner epithelium as it goes deeper into the lungs. These gives rise to further smaller bronchioles ,lobular bronchiole enters the lung lubule and these further divides to give rise to terminal bronchioles from which respiratory bronchioles originates.

$$\textbf{Option (D)}$$

$$\bullet$$ Tertiary bronchi are the segmental bronchi which arises from the division of secondary /lobar bronchi which is in turn originated from the primary bronchus entering the lungs. These bronchi lacks cartilaginous rings.

$$\textbf{Hence, the correct option is (C)}$$

$$\textbf{Correct option:A}$$ 

$$\textbf{Solution:}$$

$$\bullet$$ Carbon dioxide of about 70% is  transported as bicarbonate ions in the plasma . When carbon dioxide diffuses across the cell membrane of erythrocytes it reacts with water to produce carbonic acid which splits the very moment in the presence of carbonic anhydrase (only present in erythrocytes) to bicarbonate ions and protons (hydrogen ions) as it is very unstable,it's a reversible process.

$$\bullet$$ Hydrogen ions released to the reaction binds to hemoglobin resulting in the initiation of Bohr effect ,thus oxygen release increases,high hydrogen ions concentration in the blood makes it acidic and results in lower ph of blood.

$$\textbf{Hence, the correct option is (A)}$$

A)      Correct Option – C
B)      Explanation for correct option -

• Tidal volume is the amount of air that can be inhaled or exhaled during one respiratory cycle, which is approximately 300-500ml.
• Residual volume is the volume of air remaining in the lungs after a maximal exhalation. The normal adult value is averaged at 1200ml.
• Expiratory reserve volume is the volume of air that can be exhaled forcibly after exhalation of normal tidal volume. The normal adult value is 700-1200ml.
• Vital capacity is the total amount of air exhaled after a maximal inhalation. The value is about 4800ml.

• Emphysema is a group of lung diseases that block the airflow and make breathing difficult. 
• As in this condition, the inner walls of the air sac get rupture and creating one larger air space. 
• This reduces the surface area of the lungs and thus, reduces the amount of oxygen to reach the bloodstream. 
• Alpha-1 antitrypsin is a protease inhibitor and it is used to treat emphysema because it protects tissues from enzymes of inflammatory cells.

Hence the correct answer is (A)

• The epiglottis is a large, leaf-shaped piece of cartilage lying on top of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally.
  
• During swallowing of food the larynx elevates, causing the epiglottis to fall on the glottis (opening into larynx) like a lid, closing it off, this prevents food from entering the windpipe (trachea). Hence The structure which prevents the entry of food particles into the respiratory passage is Epiglottis.
• So, the correct answer is 'Epiglottis'.
  

• An increase in blood CO$$_2$$ concentration leads to a decrease in blood pH, i.e. blood becomes acidic.
• At acidic pH haemoglobin will release the bind oxygen.
• This causes decreased affinity of haemoglobin molecules towards oxygen.
  
• RBC count is not directly affected by blood pH.