Question

Which of the following statement(s) is (are) true about respiration?
(i) During inhalation, ribs move inward and diaphragm is raised.
(ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air.
(iii) Haemoglobin has greater affinity for carbon dioxide than oxygen.
(iv) Alveoli increase surface area for exchange of gases.

• A. (i) and (iv)
• B. (ii) and (iii)
• C. (i) and (iii)
• D. (ii) and (iv)

Answer 1

The correct option is D (ii) and (iv)

During inhalation, diaphragm contraction occurs which induces the lower ribs to move upward and forward, which also increases thoracic volume. The ribs move outward because the central tendon of the diaphragm (at the crown of the dome) pushes down onto the liver and stomach, which act like a fulcrum. Oxygen enters into the alveoli. Alveoli, is the site for gaseous exchange and they increase the surface area for facilitating the process.
Carbon monoxide has 210 times greater affinity for haemoglobin than oxygen. Thus, the correct answer is option D.