1. Endothelial cells: The innermost layer of the capillary wall is made up of a single layer of endothelial cells. These cells are very thin and have a large number of pores that allow small molecules, such as water, oxygen, and glucose, to pass through while blocking the passage of larger molecules, such as proteins and lipids.
2. Basement membrane: The basement membrane is a thin layer of material that lies beneath the endothelial cells. It is composed of a mixture of collagen, elastin, and proteoglycans. The basement membrane provides support for the endothelial cells and helps to maintain the integrity of the capillary wall.
3. Pericytes: Pericytes are small cells that are located outside of the basement membrane. They are wrapped around the capillaries and help to support them. Pericytes also play a role in regulating the flow of blood through the capillaries.
The capillary wall is a semipermeable membrane, which means that it allows some substances to pass through while blocking others. This property is essential for the proper functioning of the capillaries, as it allows the exchange of nutrients and waste products between the blood and the surrounding tissues.