Features and functions of human smooth muscle

In the walls of internal organs (stomach, intestines, uterus, bladder, etc.) and most blood vessels, there are smooth muscles formed by smooth muscle tissue.

The main functions of smooth muscles:

• in hollow organs (ureter, intestines, etc.), they maintain pressure;
• a slow contraction of smooth muscles causes undulating peristalsis of the hollow organs, which ensures the advancement of their contents and the emptying of organs;
• change the lumen of blood vessels, thereby regulating the pressure in them;
• smooth muscles located in the skin at the base of the hair follicles, when contracted, lift the hair and squeeze out fat from the sebaceous glands;
• in the eyes, smooth muscles provide the constriction and dilation of the pupil, determine the thickness of the lens.

A feature of smooth muscles is:

• slow contraction and relaxation (tens of seconds);
• the involuntary nature of the contraction (regardless of the will of the person).

Smooth muscle tissue is capable of prolonged tension and practically does not fatigue.
Example: smooth muscles located in the walls of arterial vessels are constantly in a state of contraction.