Capillaries are key components of the bloodstream. They are the thinnest and smallest of the blood vessels, and play a crucial role in the transport of nutrients, oxygen and waste products in the body.

Capillaries are located between venules and arterioles, forming "capillary beds" where blood pressure is low. Because of their fine structure and low pressure, they can easily release oxygen and essential nutrients to the cells, as well as collect metabolic waste and carbon dioxide. This process is essential to nourish the cells and remove metabolic waste.

The endothelial cells that line the walls of the capillaries are also responsible for other important functions. These cells play a role in the immune response by preventing pathogens from crossing the capillary barrier. In addition, endothelial cells can expand or contract to regulate blood pressure, ensuring proper blood flow.


Definition and Meaning

Capillaries are the smallest blood vessels in the human body, located between arterioles and venules. They have a very thin wall that allows the exchange of nutrients, oxygen and carbon dioxide between the blood and the surrounding tissues. Capillaries are present in all organs and tissues of the body and their dense network provides oxygen and essential nutrients to cells and removes waste products and carbon dioxide from their metabolism. Capillaries also play an important role in the regulation of blood pressure and the distribution of blood flow throughout the body. Exchanges between capillaries and surrounding tissues occur by diffusion, osmosis and filtration, aided by physiological processes such as vasodilation and vasoconstriction.

How capillaries work

Capillaries are organized into networks forming the "capillary beds" where pressure is lowest. They play a crucial role in the distribution of nutrients and oxygen to the cells, as well as in the evacuation of waste and CO2. Their diameter is about 8 to 10 µm, which is thinner than a hair (40 to 100 µm).


Role of the endothelial cells

The endothelial cells of the capillaries, which line the inside of the vessels, also play a role in the immune response.


Bottom line

In summary, capillaries are vital blood vessels for blood circulation, ensuring the distribution of nutrients and oxygen to cells, as well as the removal of waste products and CO2. Their thinness and distribution network make them key to the overall health of the body.