Blood Vessels
The Vascular System
The vascular system transports blood to the tissues and back to the heart. Vessels that carry blood away from the hart are arteries & arterioles. Vessels that return blood to the heart are veins & venues. Vessels that function to exchange nutrients, gases & waste between tissues and blood are capillaries.
Anatomy of Blood Vessels
There are three layers in all blood vessels, except capillaries, which are made of only tunica intima which is only one cell thick to allow for exchange.
- Tunica externa - outermost layer that forms protective covering, mostly fibrous
- Tunica media - smooth muscle & elastic tissue, controlled by the sympathetic nervous system
- Tunica intima - forms a friction-reducing lining inside the vessels
Arteries vs Veins
Arteries have a thicker tunica media than veins, because they have to hold up to the changes in pressure from the heart.
Veins have a thinner tunica media and operate under low pressure. Only veins have valves to prevent back flow.
The opening (lumen) of the veins is larger than that of the arteries.
Veins have a thinner tunica media and operate under low pressure. Only veins have valves to prevent back flow.
The opening (lumen) of the veins is larger than that of the arteries.
Crash Course, Blood Vessels, part 1
|
Crash Course, Blood Vessels, part 1
|