Give Reasons: (a) Rings of cartilage are present in the trachea. (b) Lungs always contain a residual volume of air
(a) The walls of trachea have rings of cartilage on them which prevent it from collapsing. (b) The volume of air left behind in the lungs even after forceful breathing out of air is called as residual volume. This helps to provide sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.
