Capillary blood has the slowest blood flow, which is beneficial to

The blood flow rate in capillaries is relatively slow, which helps the exchange of substances between blood and tissue cells. Capillaries are the smallest blood vessels in the cardiovascular system. This type of blood vessel can only be observed through a microscope. It is very important to human health. If there is a problem with the capillaries, it often leads to the occurrence of some diseases. Let us learn about capillaries below.

Capillary blood has the slowest blood flow rate, which is beneficial

The capillaries are very thin and only allow red blood cells to pass through in a single file. They are very thin and consist of only a layer of epithelial cells. The blood flow rate in the capillaries is very slow, which is conducive to the exchange of substances between blood and tissue cells.

Capillaries

Microvessels refer to the tiny blood vessels in the cardiovascular system, which can only be seen under a microscope. Microvessels refer to the tiny blood vessels connecting arterioles and veins. They are distributed in various tissues and organs, and their branches are connected to form a network, so they are also called terminal vascular beds. In the order of vascular branching, microvessels mainly include arterioles, capillaries and venules; some also have two short circuits directly connecting arterioles and venules: direct pathway and arteriovenous anastomosis.

Capillary composition

In tissues and organs, one or several arterioles and venules and the capillaries between them constitute the basic unit of microcirculation. Because the structures and functions of various tissues and organs are different, the distribution and composition patterns of their microvessels are unique.

① Arteriole → capillary → venule, which is a common pattern;

② Arteriole → capillary → venule, but there is an arteriovenous anastomosis between arteriole and venule;

③ Capillaries → veins → capillaries. The vein connecting the two groups of capillaries is called the portal vein. This type is rare and is found in the liver and hypothalamus-pituitary gland.

④ Input arteriole → capillary → output arteriole → capillary, seen in kidney and pancreatic islets.

Function

The functions of microcirculation in various tissues and organs are different. Some are mainly for supplying nutrition and excreting metabolic products; some are mainly for regulating or maintaining the local environment constant, such as regulating body temperature, gas exchange, excretion and hormone transport. The function of microvessels is regulated by neural and humoral factors. Some microvessels have rich vasomotor nerves, while others are sensitive to substances released by nearby cells.