Capillary Wall

The capillary endothelium is very thin, since the transfer of substances from the blood into the tissue or - e.g. in the lungs - into the breathing air takes place in the capillaries. It consists of a simple layer of endothelial cells and the basement membrane, which are supplemented by pericytes that contribute to the contraction of the capillaries. The gas and matter exchange between blood and tissue takes place through the thin capillary walls.