An Indiscriminate Amalgamation


Cells lining the blood vessel walls

The structure of the endothelium, the thin layer of cells that line our arteries and veins, is visible here. The endothelium is like a gatekeeper, controlling the movement of materials into and out of the bloodstream. Endothelial cells are held tightly together by specialized proteins that function like strong ropes (red) and others that act like cement (blue).

Image courtesy of Christopher V. Carman and Roberta Martinelli, Harvard Medical School, Boston.