chapter 13
13.1 Blood Vessles
Arteries
From heart to capillaries
Arterioles
provide blood to capillaries
capillaries
form extensive branching networks
The structure of vessel walls
- Tunica intima : innermost layer of a blood vessel.
- Tunica media: the middle layer, contains smooth muscle tissue in a frame work of collagen and elastic fibers
- Tunica externa: forms a sheath of connective tissue around the vessel. Stabalize and anchor the blood vessel.
Blood flowing out of capillaries network first enters venules that merge into veins.
Some examples of elastic arteries (large arteries) are pulmonary trunk, and aorta and their major arterial branches
The walls of elastic arteries contain tunica media dominated by elastic fibers rather than smooth.
Muscular arteries (medium arteries) distribute blood to skeletal muscles and internal organs. The thick tunica media contains more smooth than elastic.
the only blood vessels whose walls permit exchange between the blood and the surrounding interstital fluid. (cells and the blood)
Diffusion differences are small bc the walls are thin.
Consist of a single layer of endothelial cells inside a basement membrane.
function as an interconnected network called capillary bed.
entrance is guarded by precapillary sphincter, a band of smooth muscle.
Veins
The 5 general classes of blood vessels
arteries
arterioles
capillaries
venules
veins
Collect blood from all tissues and organs and return it to the heart.
more elastic than viens
carry blood at the highest pressure
blood vessel that has only a tunica intima
hold the greatest volume of blood
highest velocity of blood flow
13.2
Factors affecting blood flow
cardiovascular pressures within the systemic circuit
resistance
pressure
vascular resistance
viscosity
turbulence
interplay between pressure & resistance
venous pressure
blood pressure (arterial pressure)
capillary pressure and capillary exchange