Capillaries: The Vessels Allowing Diffusion of Gases

Capillaries are the smallest and thinnest blood vessels in the body, with a diameter of approximately 5-10 microns (µm). They are responsible for the exchange of gases, nutrients, and waste products between the blood and the tissues. Capillaries are so thin that gases such as oxygen and carbon dioxide can diffuse through their walls.

Structure of Capillaries

Capillaries consist of a single layer of endothelial cells surrounded by a basement membrane. The endothelial cells are very thin, with a diameter of only one cell, and are tightly packed together. This creates small gaps called intercellular clefts, which allow small molecules such as gases to pass through the walls of the capillaries.

Function of Capillaries

Capillaries are the site of gas exchange in the body. Oxygen from the lungs diffuses through the walls of the capillaries and into the bloodstream, while carbon dioxide produced by the body's cells diffuses out of the bloodstream and into the lungs to be exhaled. This exchange of gases occurs via diffusion, which is the movement of molecules from an area of high concentration to an area of low concentration.

Conclusion

Capillaries are the vessels that allow the diffusion of gases through their thin walls. They are responsible for the exchange of gases, nutrients, and waste products between the blood and the tissues. Capillaries consist of a single layer of endothelial cells surrounded by a basement membrane. Gases such as oxygen and carbon dioxide can diffuse through the walls of the capillaries via small gaps called intercellular clefts.

The alveoli are surrounded by tiny blood vessels, called capillaries. The alveoli and capillaries both have very thin walls, which allow the oxygen to pass from the alveoli to the blood. The capillaries then connect to larger blood vessels, called veins, which bring the oxygenated blood from the lungs to the heart.Small molecules, such as gases, lipids, and lipid-soluble molecules, can diffuse directly through the membranes of the endothelial cells of the capillary wall.