CBSE Questions for Class 11 Medical Biology Breathing And Exchange Of Gases Quiz 2 - MCQExams.com

• Rabbit is a mammal and like any other mammal they have well developed lungs to help them in respiration.
• The respiratory system starts with a pair of external nostrils present at the anterior end of the snout. 
  
• Exchange of gases takes place between the alveoli and the blood flowing within the ducts present in the walls of the alveoli.
  

Solution:

• Transport of carbon dioxide in a chemically modified form accounts for nearly 70% of total carbon dioxide transport and is achieved by carbon dioxide conversion to bicarbonate. 
• Transport of carbon dioxide in a protein bound form accounts for nearly 20% of total carbon dioxide transport and is achieved by reversible binding of carbon dioxide to haemoglobin (carbaminohaemoglobin). 

Solution

• Correct answer is option D.
• Explanation for correct option:
• Respiratory bronchioles are the final division of the bronchioles within the lung.
• They are a continuation of the terminal bronchioles and are approximately 0.5mm in size
• The function of the bronchioles is to deliver air to a diffuse network of around 300 million alveoli in the lungs.

Solution:

• Vital Capacity (VC) is the maximum volume of air that can be exhaled following a deep inspiration.
• This is the total of Inspiratory Reserve Volume (IRV) +  Tidal Volume (TV) +  Expiratory Reserve Volume (ERV)
• Total Lung Capacity (TLC) = residual volume (RV) + vital capacity (VC)
• Hence VC = TLC - RV

• Tidal Volume (TV) is the amount of volume of air that can be inspired/expired normally.
• Vital Capacity is the maximum volume of air that can be expelled from the lungs after taking the deepest possible breath.
• Residual volume is the volume of air still remaining in the lungs after the most forcible expiration possible. 
• Hence, option A is correct.

Solution

Correct answer is option A.

Explanation for correct option:

• The wall of the alveoli is very thin and has a rich network of blood capillaries.
• The alveolar capillary membrane consists mainly of squamous epithelium, epithelial basement membrane, a thin interstitial space, capillary basement membrane and capillary endothelium.
• There are 2 layers separating the air from the blood in the lungs.
• One is the squamous layer of the epithelium of the alveolar walls of the lungs and the other is the endothelium lining (innermost) of the blood vessel.

• The presence of elevated carbon dioxide levels in the blood is the stimulant that the respiratory centre responds to, in order to signal the respiratory muscles to breathe. 
• Chemoreceptors found in carotid bodies and aortic bodies are responsible for detecting a decrease in blood pH by rising $$PCO_2$$. 

• Normally the inspired air constitutes about 20.84% of oxygen whereas the expired air constitutes about 15.7% of oxygen. And even if one holds his or her breath, it is not possible to breathe out air totally without oxygen.

• The eustachian tube is a canal that connects the middle ear to the nasopharynx. It controls the pressure within the middle ear, making it equal to the air pressure outside the body. No one can breathe out air through eustachian tubes by closing both the nose and the mouth.

• Yes, one can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.

• The lungs cannot be made fully empty by forcefully breathing out all air from them. Residual volume is always present in the lungs, even after the maximum forceful expiration effort. It is about 1500 ml of the air.
• So, the correct answer is 'One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.'

Solution:
Correct answer is option B
Explanation for correct option

• Alveoli are minute air-filled sac found in the lungs of vertebrates.
• The alveoli are regions for the exchange of oxygen and carbon dioxide gases during respiration.
• These sacs are covered in a mesh of tiny blood vessels or capillaries which connect to a network of arteries and veins.
• The cells that line the alveoli are squamous epithelium cells.

• A is the alveolar cavity where exchange of respiratory gases takes place.
• B are the red blood cells mainly involved in the transport of oxygen due to presence of hemoglobin.
• C is blood capillary that branches off from pulmonary artery (transports deoxygenated blood from heart to lungs).
• D is the one cell thick alveolar membrane made up of squamous epithelium.

• The gaseous exchange between blood and air does not occur in the conductive zone. 
• The respiratory and transitory zones including alveoli constitute about 90% of the lung volume. 
• The conducting zone of the respiratory system is made up of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles; their function is to filter, warm, and moisten air and conduct it into the lungs. 
• Thus, conducting zone + respiratory zone = respiratory tract (airway).
• The respiratory zone is found deep inside the lungs and is made up of the respiratory bronchioles, alveolar ducts, and alveoli. 
• The respiratory zone is the site of O$$_2$$ and CO$$_2$$ exchange with the blood. 

• The majority (approximately 98%) of oxygen in the body is transported by hemoglobin, which is found inside red blood cells.
  
• Transport of carbon dioxide in a chemically modified form accounts for nearly 70% of total carbon dioxide transport and is achieved by carbon dioxide conversion to bicarbonate by an enzyme called carbonic anhydrase.
• Transport of carbon dioxide in a protein bound form accounts for nearly 20% of total carbon dioxide transport and is achieved by reversible binding of carbon dioxide to haemoglobin (carbaminohaemoglobin).