Arteries
Thick, muscular, elastic walls to withstand high blood pressure.
Narrow lumen for blood to flow through.
Pressure is maintained due to the elastic walls.
Veins
Less muscular and elastic; thin walls.
Wide lumen for blood to flow through.
Contains semi-lunar valves to help maintain a one-way flow of blood.
Capillaries
Walls are one cell thick, very narrow.
As diffusion distance is short it is easier to supply oxygen and remove carbon dioxide.
Blood flows through slowly, giving more time for diffusion to occur.
ARTERIOLES
Small vessels that arteries branch out into.
Allow oxygenated blood to enter the capillaries from the arteries.
VENULES
Small vessels that are formed when capillaries come together to make a vein.
Allow deoxygenated blood to return from the capillaries to the veins.
SHUNT VESSELS
A blood vessel that links an artery directly to a vein.
Allows blood to bypass the capillaries in certain areas.
Slide 4
Lymphatic system
Tissue fluid is made up of plasma and white blood cells. It acts as a bridge in the diffusion of chemicals between the capillaries and the cells of the tissue.
Oxygen and glucose diffuse from the blood into the tissue fluid and then into the cells.
Carbon dioxide and urea diffuse from the cells into the tissue fluid and then into the blood.
When the the tissue fluid drains into the lymphatic vessels, it is then called lymph. The lymph enters the blood again through the subclavian vein. On its way from the tissues to the subclavian vein, lymph flows through several lymph nodes. This is where new white blood cells are produced, which destroy most bacteria/toxins in the lymph.
