Chapter 11 – Blood Vessels:The Structure & Function of Blood Vessels

Question 1

Vascular disorders—and their downstream sequelae—are responsible for more morbidity and
mortality than any other category of human disease.

The most clinically significant lesions typically involve arteries only.

T or F

Answer 1

FALSE

Although the most clinically significant
lesions typically involve arteries, venous diseases also occur.

Question 2

Vascular pathology results in
disease via two principal mechanisms:

Answer 2

• (1) Narrowing (stenosis) or complete obstruction of vessel lumens, either progressively (e.g., by atherosclerosis) or precipitously (e.g., by thrombosis or embolism); and
• (2) weakening of vessel walls, leading to dilation or rupture.

Question 3

The general architecture and cellular composition of blood vessels are not the same throughout the
cardiovascular system.

T or F

Answer 3

FALSE

However, certain features of the vasculature vary with and reflect
distinct functional requirements at different locations ( Fig. 11-1 ). To withstand the pulsatile flow
and higher blood pressures in arteries, arterial walls are generally thicker than the walls of
veins. Arterial wall thickness gradually diminishes as the vessels become smaller, but the ratio
of wall thickness to lumen diameter becomes greater

Question 4

Answer 4

FIGURE 11-1 Regional specializations of the vasculature. Although the basic organization of
the vasculature is constant, the thickness and composition of the various layers differ
according to hemodynamic forces and tissue requirements

Question 5

What are the basic constituents of the walls of blood vessels ?

Answer 5

• endothelial cells and smooth muscle cells, and
• extracellular matrix (ECM), including elastin, collagen, and glycosoaminoglycans

Question 6

What are the three concentric layer of the blood vessel?

Answer 6

• intima,
• media, and
• adventitia—

are most clearly defined in the larger

vessels, particularly arteries.

Question 7

In normal arteries, what is the appearance of intima?

Answer 7

In normal arteries, the intima consists of a single layer of
endothelial cells with minimal underlying subendothelial connective tissue

Question 8

What separates the intima of a bv from the media?

Answer 8

a dense elastic membrane called the internal elastic lamina.

Question 9

How does the smooth muscle cell layer of the media near the vessel lumen receive oxygen and nurtrientS?

Answer 9

direct diffusion
from the vessel lumen, facilitated by holes in the internal elastic membrane.

Question 10

Since diffusion
from the lumen is inadequate for the outer portions of the media in large and medium-sized vessels, therefore how are they nourished?

Answer 10

are nourished by small arterioles arising from outside the vessel
(called vasa vasorum, literally “vessels of the vessels”) coursing into the outer one half to two
thirds of the media.

Question 11

The outer limit of the media of most arteries is a what?

Answer 11

is a well-defined external elastic lamina.

Question 12

What is external to the media?

Answer 12

adventitia,

consisting of connective tissue with nerve
fibers and the vasa vasorum.

Question 13

Based on their size and structural features, arteries are divided into three types:

Answer 13

• (1) large or elastic arteries
• (2) medium-sized or muscular arteries,
• (3) small arteries

Question 14

What are your large or elastic arteries?

Answer 14

• including the aorta,
• its large branches (particularly the innominate, subclavian, common carotid, and iliac),
• and pulmonary arteries;

Question 15

What are your medium-sized or muscular arteries?

Answer 15

medium-sized or muscular arteries,
comprising other branches of the aorta (e.g., coronary and renal arteries);

Question 16

What are your small arteries?

Answer 16

small
arteries (less than approximately 2 mm in diameter) and arterioles (20 to 100 μm in diameter),
within the substance of tissues and organs.

Question 17

The relative amount and configuration of the basic constituents differ along the arterial system
owing to local adaptations to mechanical or metabolic needs.

T or F

Answer 17

True

Question 18

The relative amount and configuration of the basic constituents differ along the arterial system
owing to local adaptations to mechanical or metabolic needs.

These structural variations, from
location to location, are principally in the __________

Answer 18

media and in the ECM

In the elastic arteries the media
is rich in elastic fibers.

This allows vessels such as the aorta to expand during systole and recoil
during diastole, thus propelling blood through the peripheral vascular system. With aging, the
aorta loses elasticity, and large vessels expand less readily, particularly when blood pressure is
increased.

Question 19

What is the reason for the elastic arteries the media to be rich in elastic fibers?

Answer 19

This allows vessels such as the aorta to expand during systole and recoil during diastole, thus propelling blood through the peripheral vascular system.

With aging, the aorta loses elasticity, and large vessels expand less readily, particularly when blood pressure is increased.

Question 20

What is the composition of muscular arteries media?

Answer 20

• *predominantly of circularly or**
• *spirally arranged smooth muscle cells**.

Question 21

How do the muscular arteries and arterioled gets regulated?

Answer 21

In the muscular arteries and arterioles (see below),
regional blood flow and blood pressure are regulated by changes in lumen size through smooth
muscle cell contraction (vasoconstriction) or relaxation (vasodilation), controlled in part by the
autonomic nervous system and in part by local metabolic factors and cellular interactions.

Since
the resistance of a tube to fluid flow is inversely proportional to the fourth power of the diameter
(i.e., halving the diameter increases resistance 16-fold), small changes in the lumen size of small arteries caused by structural change or vasoconstriction can have a profound effect.

Thus, arterioles are the principal points of physiologic resistance to blood flow .

Question 22

Why do arterioles are the principal points of physiologic resistance to blood flow .

Answer 22

Since the resistance of a tube to fluid flow is inversely proportional to the fourth power of the diameter
(i.e., halving the diameter increases resistance 16-fold), small changes in the lumen size of small arteries caused by structural change or vasoconstriction can have a profound effect.

Thus, arterioles are the principal points of physiologic resistance to blood flow .

Question 23

Describe the capillaries.

Answer 23

• approximately the diameter of a red blood cell (7 to 8 μm),
• have an endothelial cell lining but no media.

Question 24

Why do have a very large total cross-sectional area; within the capillaries, the flow rate slows dramatically?

Answer 24

With thin walls only and slow flow, capillaries are ideally suited to the rapid exchange of diffusible substances between blood and tissues.

As

normal tissue function depends on an adequate supply of oxygen through blood vessels, and since diffusion of oxygen in solid tissues is inefficient over distances of greater than approximately 100 μm, [1] the capillary network of most tissues is very rich.

Metabolically highly
active tissues, such as the myocardium, have the highest density of capillaries.

Question 25

What has the highest density of capillaries?

Answer 25

• *Metabolically highly**
• *active tissues**, such as the myocardium, have the highest density of capillaries.

Question 26

What is the sequence of blood from capillary beds?

Answer 26

Blood from capillary beds flows initially into the postcapillary venules and then sequentially
through collecting venules and small, medium, and large veins.

In many types of inflammation,
vascular leakage and leukocyte exudation occur preferentially in postcapillary venules

Question 27

In many types of inflammation,
vascular leakage and leukocyte exudation occur preferentially where?

Answer 27

postcapillary venules

Question 28

Why do veins are predisposed to irregular dilation, compression, and easy penetration by tumors and inflammatory processes.

Answer 28

Relative to arteries, veins have larger diameters, larger lumens, and thinner and less well organized walls (see Fig. 11-1 ).

Thus, because of their poor support, veins are predisposed to irregular dilation, compression, and easy penetration by tumors and inflammatory processes.

Question 29

Relative to arteries, veins have what?

Answer 29

• larger diameters,
• larger lumens, and
• thinner and less well organized walls (see Fig. 11-1 ).

Question 30

The venous system collectively has a large capacity; approximately two thirds of all the blood is
in veins.

T o F

Answer 30

True

The venous system collectively has a large capacity; approximately two thirds of all the blood is
in veins.

Question 31

How do veins get protected from reverse flow in the extremities?

Answer 31

Reverse flow is prevented by venous valves in the extremities, where blood flows against gravity.

Question 32

Describe the lymphatics.

Answer 32

Lymphatics are thin-walled, endothelium-lined channels that serve as a drainage system for
returning interstitial tissue fluid and inflammatory cells to the blood.

Lymphatics constitute an
important pathway for disease dissemination through transport of bacteria and tumor cells to
distant sites.