Final answer:
Endothelial cells form a physical lining of the heart and blood vessels, regulate molecule transport, and are involved in angiogenesis but do not contract and relax to maintain blood flow.
Step-by-step explanation:
All of the following are functions of endothelial cells except contract and relax to maintain blood flow. Endothelial cells have several important functions:
- They provide a physical lining in the heart and blood vessels.
- They regulate the transport of molecules in and out of the capillaries, such as gases, nutrients, and wastes.
- They play a major role in the process of angiogenesis, which is the development of new blood vessels.
However, they do not contract and relax. The contraction and relaxation to regulate blood flow is a function of the smooth muscle surrounding the blood vessels, not the endothelial cells themselves.
Endothelins secreted by endothelial cells are potent vasoconstrictors; they help establish a balance with vasodilators and have a role in the regulation of blood pressure. But again, the endothelial cells do not contract and relax as muscles do.