question_answer 48)

    Which of the following statements (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 form 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 increases surface area for exchange of gases (a) (i) and (iv)                     (b) (ii) and (iii)                    (c) (i) and (iii)                     (d) (ii) and (iv)

Answer:

                  (d) When we breathe in, we lift our ribs and flatten our diaphragm, the chest cavity becomes larger. Alveoli is balloon like structure which provides a surface where the exchange of gases occurs the walls of alveoli consist of network of blood-vessels. The air is sucked into the lungs to fill the expanded alveoli, The blood brings carbon dioxide from the rest of the body for release info the alveoli and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. In human beings, the respiratory pigment is hemoglobin which has a very high affinity for oxygen. This pigment is present in the red blood corpuscles.   The human lungs have millions of air sacs called alveoli whose surface area is many times that of the body. These are involved in exchange of gases.