CVS

5 classes of blood vessels

arteries, arterioles, capillaries, venules, veins

single inner layer all vessels share…

endothelial cells

three main structural layers

Tunica intima (inner)

Tunica media (middle - muscle/elastic)

Tunica externa (outer - connective tissue)

tunica intima

the innermost layer of a blood vessel

Tunica media

middle layer of artery; made up of smooth muscle fibers and thick layer of elastic connective tissue

Tunica externa

outer layer of a blood vessel which connects it to surrounding tissues

arteries

Carry oxygenated blood away from the heart (except pulmonary artery).

They have thick, elastic, and muscular walls to handle high pressure.

Elastic arteries

closer to the heart; allow stretch as blood is pumped into them and recoil when ventricles relax

Muscular arteries

distribute blood to skeletal muscles and internal organs

arterioles

smallest arteries, mostly smooth muscle, control flow to capillaries.

capilleries

small vessels that carry blood from arteries to your veins. Sites of exchange: oxygen, nutrients, waste between blood & tissues.

Thin walls (single endothelial layer), slow blood flow.

Continious capillaries

tight junctions.

Fenestrated Capillaries

pores (e.g., in kidneys, intestines).

precapillary sphincters

Regulate blood flow into capillary beds.

Vasomotion

rhythmic opening/closing of sphincters to adjust blood flow based on local chemical needs.

veins

Return deoxygenated blood to the heart (except pulmonary vein).

Thinner walls and lower pressure than arteries.

Contain valves to prevent backflow.

valve

A flap of tissue in the heart or a vein that prevents blood from flowing backward.

Venules

small, collect blood from capillaries.