Blood Vessels
Once the blood leaves your heart, it goes through a complex network of blood vessels. There are two types of blood vessels: veins and arteries. Veins are the blood vessels that carry blood back to the heart (oxygen poor blood). Arteries carry blood away from the heart (oxygen rich blood). The blood circulates throughout your body and is pumped to every cell in your body in less that a minute.
Capillaries are also very important. They are the smallest blood vessels in your body. Capillaries are so thin that they allow diffusion to occur through there walls allowing the exchange of nutrients and waste. Capillaries are located throughout the tissues and connect to the arteries and veins.
Arteries and veins are structurally identical. They both have three layers. The outer layer is the tunica externa, the middle layer is the tunica media, and the innermost layer is the tunica interna. The tunica media is the expandable layer which allows different amounts of blood to flow through. Although they both have these three layers, arteries do not have valves as veins do.
Capillaries are also very important. They are the smallest blood vessels in your body. Capillaries are so thin that they allow diffusion to occur through there walls allowing the exchange of nutrients and waste. Capillaries are located throughout the tissues and connect to the arteries and veins.
Arteries and veins are structurally identical. They both have three layers. The outer layer is the tunica externa, the middle layer is the tunica media, and the innermost layer is the tunica interna. The tunica media is the expandable layer which allows different amounts of blood to flow through. Although they both have these three layers, arteries do not have valves as veins do.