Question

What is the function of capillary blood vessels?

Answer 1

Hint: There are two types of circulatory systems found in the animal kingdom- the open blood circulatory system, and, closed blood circulatory system.
In the closed blood circulatory system, the blood is carried to the tissues via some special tubes and not directly poured into the body cavity. These tubes are known as vessels.

Complete answer:
The closed blood circulatory system consists of three types of vessels:
Arteries: These are the blood vessels that carry blood away from the heart, i.e., from the heart towards the different organs of the body.
Veins: These are the blood vessels that carry blood towards the heart. i.e., from the organs to the heart.
Capillaries: These are the tiniest and the narrowest of the blood vessels through which gaseous exchange between the tissues and blood along with the passage of nutrients can take place.
The walls of both the arteries and the veins are too thick to allow any exchange of gases or nutrients from the blood with the corresponding tissues that surround them. They particularly serve as a central vessel to bring blood from or to the heart (like a canal that brings water to the fields!). Now, the arteries near the tissues/organs branch off from the mainline to form narrower and thinner branches to efficiently distribute around the organs.
At first, they form smaller arterioles. With further repeated branching they become thinner and thinner and ultimately form capillaries- through which the gaseous exchange and passage of nutrients can easily take place.
Now after the gaseous and nutrient exchange, the blood becomes saturated with carbon dioxide and waste materials. These capillaries then unite to form venules which ultimately unit to form veins.

Note:
Thus, it should be noted that the capillaries are the main vessels through which gaseous exchange and nutrient supply to the tissues/organs of the body occurs. They have a very thin wall through which the diffusion of gases and nutrients is possible.