blood vessel biology

Blood vessels are part of the circulatory system, acting as channels that carry blood throughout the body. They consist of three main types: arteries, which carry oxygen-rich blood from the heart; veins, which return oxygen-poor blood back to the heart; and capillaries, tiny vessels where nutrient and gas exchange occurs between blood and tissues. Blood vessels are lined with cells called endothelium, which help regulate blood flow, blood pressure, and immune responses. They also have smooth muscle layers that allow them to constrict or dilate, adjusting blood flow as needed for different tissues and activities.