Question

How can arteries contract and expand?

Answer 1

Hint: Arteries are the part of the circulatory system. The blood vessels which carry oxygenated blood from the heart to all the parts of the body is called the artery. The arteries are responsible for maintaining the pH of the blood.

Complete answer:
To solve this question, we must know about the structure of arteries.
The arteries and arterioles carry blood away from the heart. The artery is composed of many layers which is capable of expansion and contraction. This expansion and contraction help in maintaining regular blood pressure and also regulate the flow of blood from the heart.

Walls of Artery-
The outermost layer is called tunica externa which is made up of collagen and elastic tissues. It is connected with the connective tissue.
The middle layer is known as tunica media which is made up of smooth muscles which are involuntary in nature.

The innermost layer called the tunica intima is made up of elastic tissues and endothelial cells. The blood flows through the hollow cavity called the lumen.
Contraction and expansion of artery-
The expansion of the blood vessels is called vasodilation. The vasodilation takes place when the smooth muscles in the walls of the artery relax. This makes blood vessels open. As a result, the flow of blood through the vessel increases therefore the blood pressure decreases.

When the blood flow in the organ decreases, the arterioles dilate to reduce friction. The smooth muscles are responsible for the contraction. When the perfusion of blood increases, the smooth muscles expand which leads to the contraction of the artery. When the artery constricts, the flow of blood is decreased. This is called vasoconstriction. This helps in retaining the body heat.

Note: The arteries have a thick layered wall so as to withstand high blood pressure in the arteries. Also, the diameter of the blood vessel is responsible for maintaining the flow of blood. Aorta is the largest artery which carries blood from heart to all parts of the body.