Question

Which of the following is not a function of air sacs?
(a) Act as balloons
(b) Accessory respiratory pigments
(c) Temperature regulations
(d) Storage of food

Answer 1

In birds, the process of respiration is similar to the process of respiration in mammals with some differences that is air passes through the lungs twice to absorb the oxygen in double amounts. They are endothermic in nature.

Complete answer:
Birds undergo double respiration where the lungs and air sacs are connected for enough supply of oxygen. The process by which inhaled oxygen is used twice for the process of respiration is known as double respiration. This phenomenon of double respiration exhibits in birds.
Respiratory Cycle of a Bird.
-During the first inspiration, the air travels through the nostrils, of a bird into the nasal cavity. From there it passes via the larynx into the trachea. Air moves through the trachea to the syrinx, then to the caudal (posterior) air sacs. A small amount of air will pass to the lungs through the caudal air sacs.
-During the process of first expiration, the air is moved from the posterior air sacs into the lungs. The bronchi continue to divide into capillaries. These blood capillaries flow through the air capillaries and that is the place where the oxygen and carbon dioxide are exchanged.
-The air moves to the cranial air sacs during the second inspiration.
-At the second expiration, the air moves out of the cranial air sacs, via the syrinx into the trachea, then through the larynx, finally reaches the nasal cavity and then out of the nostrils.

So, the correct answer is ‘Storage of food’.

Note:
The muscles involved in this process of double respiration are intercostal muscles, abdominal muscles, and sternum. Air sacks are unidirectional in birds and allow the flow of oxygen only during inspiration or expiration while in other mammals both take place simultaneously.