Q.) Carefully study the diagram of the human
respiratory system with labels (i), (ii), (iii)
and (iv). Select the option which gives
correct identification and main function
and /or characteristic.
(a) (i) Trachea: It is supported by bony rings for conducting inspired air.
(b) (ii) Ribs: When we breathe out, ribs are lifted.
(c) (iii) Alveoli: Thin-walled sac like structures for exchange of gases.
(d) (iv) Diaphragm: It is pulled up when we breathe in.
Ans. (c) (iii) Aveoli: Thin-walled sac like structures for exchange of gases.
Explanation: Trachea is supported by rings of cartilages to prevent it from collapsing when there is not air present in it. When we breathe out, the muscles of diaphragm and ribs relax and the diaphragm and muscles attached to ribs contract when we breathe in.