Give suitable explanations for the following:
(a) Breathing through the nose is said to be healthier than through the mouth.
(b) Why does gaseous exchange continue in the lungs even during expiration?
(c) Why does a person feel breathlessness at higher altitudes?
(d) Why do you shiver and why do your teeth chatter when it is very cold in winter?

(a) It is because the hair in the nostrils checks and prevents the large/tiny dust particles from entering the respiratory system.

(b) It is because expiration is the outcome of reverse movements of the diaphragms and ribs. As a result of the movements of the diaphragm and the ribs, the thoracic cavity shrinks and the lungs compress causing the air to be forced out of the body into the environment.

(c) A person feels breathlessness at higher altitudes because as we go up higher, the content of oxygen is lower in the air.

(d) We shiver and our teeth chatter when it is very cold in order to increase the heat production in the body. To maintain the temperature of the body constant in extremely cold conditions, the production of heat is increased through heightened metabolic rate and greater muscular activity and shivering and teeth chattering involves a lot of muscular activity.