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

  1. Tunica intima : innermost layer of a blood vessel.
  1. Tunica media: the middle layer, contains smooth muscle tissue in a frame work of collagen and elastic fibers
  1. 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