Angiogenesis is defined as which process?

• A. Formation of new capillaries and arterioles in response to hypoxic stress.
• B. Dilation of existing arteries.
• C. Shrinkage of capillary networks.
• D. Reduction in blood vessel formation.

Answer: (D)

Angiogenesis is the growth of new blood vessels from existing ones, expanding the capillary and small-arteriole network to improve blood supply. This process is typically triggered by hypoxic stress, with signals like VEGF guiding endothelial cells to proliferate and form new vessels. It is distinct from vasodilation, which widens existing arteries, from shrinkage or pruning of vessels, and from a general reduction in vessel formation. So the defining idea is the formation of new capillaries and arterioles in response to low oxygen or other signals.