ANATOMY

Detailed explanation-1: -Lungs contain specialised structures called alveoli which are the site of exchange of oxygen and carbon dioxide between the blood and air. Hence, the alveoli are responsible for absorption of oxygen into the blood.

Detailed explanation-2: -When we breathe in, the millions of air sacs in the lungs fill with fresh oxygenated air. The oxygen then moves into the blood by passing first through the very thin walls of the air sacs and then into the capillaries, which are tiny blood vessels in a network within the lungs.

Detailed explanation-3: -Gills are made of thin tissue filaments that are highly branched and folded. When water passes over the gills, the dissolved oxygen in water rapidly diffuses across the gills into the bloodstream. The circulatory system can then carry the oxygenated blood to the other parts of the body.

Detailed explanation-4: -The circulatory system The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body.