Unit 2: Blood Flow and Pressure Part B

Question 1

Basic vessel structure

Answer 1

depending on the vessel, they will have some or all of the following components:

a. Tunica intima
b. Elastica interna
c. Tunica media
d. Elastica externa
e. Tunica externa

Question 2

Walls of blood vessels:

Answer 2

layers of smooth muscle, elastic CT, & fibrous CT
- inner lining is a thin layer of ENDOTHELIUM

Question 3

Tunica intima

Answer 3

(innermost)

i. Single layer of endothelial cells.
ii. Continuous with endothelial lining (endocardium) of heart.
iii. These cells can secrete paracrines that regulate blood flow.

Question 4

Elastica interna

Answer 4

Made of elastic protein fibers (elastin) that are capable of stretch and recoil

Question 5

Tunica media

Answer 5

Smooth muscle - contraction and relaxation changes vessel radius.
Contraction = vasoconstriction; relaxation = vasodilation

Question 6

Elastica externa

Answer 6

layer of elastin

Question 7

Tunica externa

Answer 7

outer layer of connective tissue

Question 8

Arteries

Answer 8

a. Thick walls with lots of elastic tissue.
b. Large elastic arteries like aorta have very large diameters
(radii) that offer little resistance to blood flow (F = ∆P/R)
c. Are a pressure reservoir that helps to maintain:
i. the driving force of of blood flow during ventricular
relaxation (diastole).
ii. the constant flow of blood toward capillaries.
d. Elasticity of arterial walls allows them to stretch out (expand)
to accommodate blood coming from the ventricle during
ejection, but also acts to maintain pressure on that blood
due to the thickness of the wall and the passive elastic recoil
that occurs, pushing excess blood downstream.
e. These are low compliance (aka low capacitance) vessels. I.e.
the ability of the vessel to stretch and increase volume with
increasing transmural pressure is low (∆ volume / ∆
transmural pressure = low). Like trying to blow up a tire vs a balloon.