What do you think of this as a starter to blood vessels and function?

Question

Arteries
•Carry oxygen rich oxygen from heart to tissues and organs around the body.
•Blood flows through arteries with great force of flow, so arterial walls are thick and flexible. They are made up of three muscle layers, combining of connective tissue and elastic-like tissues. These thicker walls help protect against damage to the artery walls from the high pressure.
•Arteries get smaller and smaller the further they get away from the heart, becoming capillaries at their smallest point.

Capillaries
•Connect arteries to veins
•Carries blood to and from every cell in the body
•Capillary walls are very thin, and are composed of only a single layer of epithelia cells. As the layer is so thin, it allows for the diffusion of molecules such as oxygen, water and lipids to enter tissues. Also, carbon dioxide and urea (and other toxins) can be diffused into the blood for removal from the body.
•The endothelium also uses active transport to transport and other substances that are to

too big to diffuse across. Vesicles in the capillaries use endocytosis and exocytosis to assist this and transport material between blood and tissues (and vice versa).

Veins
•carry deoxygenated blood back to the heart.
•Due to the lack of oxygen, the pressure is much lower, meaning walls of veins are much thinner in comparison to artery walls.
•Have a collagen outer layer, maintains blood pressure.
•Have helical bands of smooth muscle to help assist and maintain blood flow to the right atrium.
•Also have venous valves to prevent black flow of blood (as the pressure is lower).

Answer 1

I studied this greatly as a biology major, and some graduate work in human anatomy and physiology. It sounds like an excellent description of the circulatory system.

Answer 2

Great for a start!

Here’s what I would add (Entries with ** are more important)

Couple of corrections.
**Not all arteries carry oxygen rich blood. The major exception if the pulmonary artery that transports deoxygenated blood from the right side of the heart to the lungs.
Blood flows with a moderate pressure (typically 120-180 mmHg).
**Arterial walls are flexible to smooth out the flow, but the larger ones also contain smooth muscle.
**This muscle is one of the mechanisms used to regulate blood pressure.
As a general principle arteries get smaller, but there are some very small arteries that branch off directly from the aorta. (e.g. Coronaries, pulmonic, lumbars, phrenic, etc)

Capillaries:
end in beds that supply areas of tissue with oxygen, but not all tissues are in direct contact with capillary beds (e.g. the lens of the eye, most cartilage)

Veins:
**Also, pulmonary vein is the exception that carries oxygenated blood back to the heart from the lungs.
**Vein lack smooth muscle, which is part of why they are thinner. The other part is that they deal with a much lower pressure than arteries. Oxygen, itself, has nothing to do with it.
**Not all veins have valves.
The muscle pump, which is where veins in the extremities (especially the lower ext) are squeezed between muscles, assists blood in returning to the heart.
As noted above, arteries maintain blood pressure, not veins. Veins are actually designed to expand and act as a reservoir for blood in the body (60-80% of blood is in the venous side of the circulation system).

The only major part missing was any discussion about the lymphatic system. This is the sewer system that returns the fluid, that leaked out of the arteries, capillaries and veins, back into the circulation.

Answer 3

just about covers it!