CBSE Questions for Class 11 Medical Biology Breathing And Exchange Of Gases Quiz 1 - MCQExams.com

• The number of alveoli in the human lungs has been estimated to be approximately 300 million.
  
• This enormous number of alveoli are meant to increase surface area of lungs for diffusion of gases. Hence, Option D is correct.
  

• Asthma is an inflammatory disease of the lungs. In this condition, airways of the lungs become narrow and swell and produce excess mucus. Due to this, the respiratory surface decreases. Symptoms include reversible airflow obstruction, bronchospasm, wheezing, coughing, shortness of breath. 
  
  
• Emphysema is also a lung disease that results in shortness of breath is caused airways of the lungs to collapse and inflammation of bronchioles. Symptoms include coughing, wheezing, shortness of breath
  
  
• Thus, the correct answer is option B.

• Asthma may be attributed to allergic reaction of the mast cells in the lungs.
• Asthma symptoms, which include coughing, wheezing, and chest tightness, are common in an asthma attack. Sometimes asthma is called bronchial asthma or reactive airway disease. 
• Mast cells secrete the autacoid mediators histamine, prostaglandin (PG) D2, and leukotriene (LT) C4, which are capable of inducing bronchoconstriction, mucus secretion, and mucosal edema, all features of asthma.
• So, the correct answer is 'Allergic reaction of the mast cells in the lungs'
  

a) Tidal volume is the volume of air displaced between normal inspiration and expiration without an extra effort. In a healthy human, it is approximately 500-550 mL.

b) Inspiratory reserve volume (IRV) is the maximal amount of air that can be inhaled into the lungs by after normal inspiration. In a healthy human, it is approximately 2500-3000 mL.

c) Expiratory reserve volume (ERV) is the maximal amount of air that can be expelled out from the lungs after normal expiration. In a healthy human, it is approximately 1000-1100 mL.

d) Residual volume (RV) is the volume of air that remains in the lungs after the most forcible expiration. In a healthy human, it is approximately 1100-1200 mL.

Thus, the correct answer is option D.

• Tidal volume is the volume of air inspired or expired with the normal breathing because adult person contains 500 ml expired or inspired volumes of air with each normal breath.
• A healthy man can inspire or expire approximately 6000 to 8000 ml of air per minute
• So, the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'

Spirometry (meaning the measuring of breath)

A. The inspiratory capacity (IC) is the amount of air that can be inhaled after the end of a normal expiration.

B. Residual volume (RV) is the air remaining in the lungs after a maximal exhalation. Naturally, the residual volume cannot be determined directly using spirometry since it is not possible to measure the remaining air volume after maximum expiration.

C. Expiratory reserve volume (ERV) is the maximal volume of air that can be exhaled from the end-expiratory position.

D. Inspiratory reserve volume (IRV) is the maximal volume that can be inhaled from the end-inspiratory level.

So, the correct answer is ‘RV’.

• The lungs are the primary organs of the respiratory system in humans and many other animals. Human lung size is determined by genetics, gender, and height. 
• Different animals exhibit different lung capacities based on their activities. For example, cheetahs have evolved a much higher lung capacity than humans in order to provide oxygen to all the muscles in the body, allowing them to run very fast. 
• Elephants also have a high lung capacity due to their large body and their need to take up oxygen in accordance with their body size. Hence, elephants and cheetahs have higher lung capacities than humans. 
  

• Some amount of air remains behind in the various parts of the respiratory tract.
• The air in the trachea and bronchi (where no diffusion occurs) is called dead space air.
• The air remaining in the alveoli or air sacs in alveolar air. The maximum volume of air that can be exchanged in one breath in and out is called the vital capacity. It is about 5000 ml. 
  
  

 A. Tidal volume - (iii) 500 mL of air

B. Inspiratory reserve volume - (i) 2500-3000 mL of air

C. Expiratory reserve volume - (ii) 1000 mL of air

D. Residual volume - (v) 1200 mL of air

E. Vital capacity - (iv) 3400-4800 mL of air

So, the correct answer is A-(iii), B-(i),C-(ii), D-(v), E-(iv)'.