An inner layer of endothelial cells is found in:
a) I only
b) I and II
c) II and III
d) I, II, and III
The innermost layer of all blood vessels is made of endothelial cells. Choice d) is correct. Other characteristics commonly tested on the MCAT include: valves are found in veins only, nutrients diffuse in and out of capillaries only, a smooth muscle layer is found in arteries and veins but not capillaries.
a) I only, incorrect, Veins and capillaries both have endothelial cells.
b) I and II, incorrect, Capillaries have endothelial cells.
c) II and III, incorrect, Arteries have endothelial cells.
d) I, II, and III, correct, Endothelial cells are found in the innermost layer of all blood vessels.