Endothelial cells line the blood vessels of the circulatory system, and are simple squamous epithelial cells. These cells will be covered in more detail in the section on the circulatory system. They are connected to each other by tight junctions.

Pericytes (Peri- around) are cells that lie close to the endothelial cells of blood capillaries and small venules into which the capillaries drain.

They are a potential source of new fibroblasts and smooth muscle cells, and help to repair damage.