Capillary vessel

Capillary Vessel

A capillary vessel or simply capillary is the smallest type of blood vessel in the body of mammals, including humans. Capillaries are part of the microcirculation system within the cardiovascular system, and they play a crucial role in the exchange of oxygen, nutrients, and waste materials between the blood and the body tissues.

Structure

Capillaries are extremely thin and have a diameter of about 5 to 10 micrometres, which is just large enough to allow red blood cells to pass through them in single file. The walls of capillaries are composed of a single layer of endothelial cells, which are surrounded by a thin layer of basement membrane.

Function

The primary function of capillaries is to facilitate the exchange of materials between the blood and the body tissues. This is achieved through the process of diffusion, filtration, and osmosis. Oxygen and nutrients diffuse from the blood in the capillaries into the tissues, while waste products such as carbon dioxide diffuse from the tissues into the blood.

Types of Capillaries

There are three main types of capillaries: continuous, fenestrated, and sinusoidal. Continuous capillaries are the most common type and are found in most tissues of the body. Fenestrated capillaries have pores in their walls and are found in organs that require rapid exchange of materials, such as the kidneys and the small intestine. Sinusoidal capillaries have large gaps between their endothelial cells and are found in the liver, bone marrow, and spleen.

Clinical Significance

Capillaries play a crucial role in many disease processes. For example, in diabetes mellitus, damage to the capillaries in the retina can lead to diabetic retinopathy, a leading cause of blindness. In addition, capillaries are involved in the formation of edema, which is the accumulation of fluid in the tissues.

See Also

• Blood vessel
• Microcirculation
• Cardiovascular system
• Endothelial cell