Structure and Function of Blood Vessels

Question 1

What are the 2 types of circulation that form the 2 pumps of the heart

Answer 1

Pulmonary circulation - the first pump properly the blood through the vessels in the lungs
Systemic circulation - the second pump propels blood through the vessels in other tissues of the body

Question 2

What are the roles of the arterioles, capillaries and venules

Answer 2

Arterioles - regulates blood flow and pressure
Capillaries - nutrient and waste exchange
Venule - allow deoxygenated blood to return to from capillaries to the veins

Question 3

What is the function of the CVS

Answer 3

• Rapid supply of oxygen and nutrients
• Rapid waste removal
• Control system of body temperature and hormone distribution

Question 4

What drives blood flow

Answer 4

• Pressure gradient (DeltaP)

- heart raises blood pressure in arteries and vein blood pressure is lower

Question 5

What is darcy’s law

Answer 5

Flow (dotted Q) = Delta P/Resistance

Question 6

What causes flow resistance

Answer 6

Resistance is due to friction between blood and the internal surface of the vessel and between blood constituents

Question 7

What is resistance inversely proportional to

Answer 7

The fourth power of the vessel radius

Question 8

How would a small increase in vessel radius affects flow resistance

Answer 8

Large decrease in resistance

Question 9

How would a small decrease in vessel radius affect flow resistance

Answer 9

Large increase

Question 10

What are the units of BP

Answer 10

Force per unit area

Question 11

Where does the main pressure drop come from in the blood vessels

Answer 11

The arterioles - the highest resistance vessels

Question 12

Describe laminar blood flow

Answer 12

All particles in the fluid are flowing parallel to the wall of the tube, particles at centre flowing fastest, particles at the edge have almost no velocity

Question 13

Describe turbulent blood flow

Answer 13

Particles follow an irregular pattern and may develop whirlpools in the blood vessels.
Sets up vibrations in the blood vessel wall and makes noises which are called murmurs

Question 14

What is the critical velocity relating to blood flow

Answer 14

This is the blood flow velocity at which there is a transition from laminar to turbulent flow

Question 15

What factors can increase the likelihood of turbulent flow

Answer 15

Increased flow velocity
Increased vessel radius
Increased blood density
Decreased blood viscosity

Question 16

What is reynolds number and what is its equation

Answer 16

This number shows the tendency towards turbulence

Re = (v x L x p(density))/n (viscosity)

Question 17

What is the main thing that determines the viscosity of the blood

Answer 17

The haematocrit, which is the percentage of blood volume that is occupied by the red blood cells

Question 18

How can viscosity be expressed

Answer 18

As relative viscosity, relative to water

Question 19

What is the relative viscosity of blood plasma and normal blood

Answer 19

Plasma = 1.3
Blood = 2.4

Question 20

What are the 3 layers of the blood vessel walls, except capillaries

Answer 20

Tunica Intima (inner layer)
Tunica Media (middle layer)
Tunica Adventitia (outer layer)

Question 21

Describe the structure and function of the Tunica Intima

Answer 21

Structure - consists of endothelial cells
Function - provides a barrier between blood and the rest of the vessel, filtration controls the passage of white blood cells

Question 22

What is the structure and function of the Tunica Media

Answer 22

Structure - Two layers of elastic tissue, the internal and external elastic laminae that sandwich a layer of smooth muscle
Function - source of mechanical strength and the smooth muscle is a means of altering the vessel diameter

Question 23

What is the structure and function of the Tunica Adventitia

Answer 23

Structure - layer of connective tissue containing fibrous tissue
Function - holds the blood vessel in place, provides mechanical strength, prevents over-expansion

Question 24

What is the vasa vasorum and where is it found

Answer 24

the small blood vessels that supply the walls of the larger blood vessels with nutrients and this runs through the connective tissue

Question 25

What are the tissues that make up large arteries and what is their use

Answer 25

Made of both fibrous (collagen) and elastic tissue.

Elastic tissue so the arteries can expand and contract during the cardiac cycle.

Question 26

What are the tissues that make up the small arteries and what are these arteries involved in

Answer 26

Less fibrous tissue but has more smooth muscle than large arteries.
More involved in circulatory control mechanisms.

Question 27

What is the main component of arterioles and what are they used for

Answer 27

smooth muscle is a major component so that contraction and blood flow can be regulated

Question 28

What are capillaries made up of

Answer 28

Single layer of endothelial cells, no tunica media or tunica adventitia

Question 29

What is the role of capillaries

Answer 29

Site of exchange of nutrients and waste products between the circulation and interstitial fluid that surrounds the cells

Question 30

What are venules made up of and what is their role

Answer 30

Have an endothelial lining together with a small amount of fibrous tissue
They are an important site of movement and water (lymphatic drainage)

Question 31

What tissues main up the veins

Answer 31

Elastic and fibrous tissues and also smooth muscle but in small amounts compared to arteries.

Question 32

What is the critical closing pressure

Answer 32

If the pressure gradient across the wall of a blood vessel falls below a certain limiting value then the vessel will collapse.
The transmural pressure at which flow ceases is the critical closing pressure.
In other words there has to be a certain pressure inside the vessel in order to keep it inflated

Question 33

In healthy individuals why are vessels constricted and dilated

Answer 33

This can be done to divert blood flow to match metabolic needs