Ch. 21 – Circulation (just a small portion of the chapter)

21.1 Compare and contrast arteries to veins Artery – away from heart ▫Most pressure ▫Aorta = 1” diameter Arteriole – small branches of arteries ▫Pressure ▫1 million Capillary – site of diffusion ▫10 billion ▫Width of RBC ▫Over 25, 000 miles total Venuole – small and collect into veins Vein – return to heart ▫Have valves to counter gravity

DIFFUSION Gaseous and chemical exchange Between interstitial fluids and blood DIFFUSION ! DIFFUSION ! DIFFUSION ! Most cells are < 125  m from a capillary Movement through caps is very slow

Pressure gradient High in arteries Low in veins Vasoconstriction = vessels narrow, smaller diameter Vasodilation = vessels enlarge, larger lumen

Patterns found in arteries and veins 1.Veins and arteries usually run parallel to each other, similar on right and left sides of the body 2.Frequently have multiple names as they pass through boundaries in the body – external iliac artery becomes the femoral artery as it leaves pelvis and goes into leg 3.Complexes of veins and arteries called anastomoses service tissues and organs – reduces risk if vessel is blocked (occluded)