Arteries, Veins and Control of Peripheral Vascular Resistance

Question 1

What types of blood vessels are in the CV system?

Answer 1

• Large arteries
• Capillaries
• Arterioles
• Venules
• Veins

Question 2

Is the structure of blood vessels in the CV system adapted to their role?

Answer 2

YES

Question 3

What are the components of blood vessels?

Answer 3

• Endothelial cells
• Vascular smooth muscle
• Elastin and collagen

Question 4

What does endothelial cells do in blood vessels and why are they important?

Answer 4

• Line all vessels and inside of heart chambers
• Important for local blood pressure control
• Prevent platelet aggregation and blood clot formation
• Angiogenesis and vessel remodelling
• Permeability barrier for nutrients/fluid between plasma and interstitial fluid

Question 5

What does vascular smooth muscle do in blood vessels and why are they important?

Answer 5

• Present in all vessels with exception of smallest capillaries
• Determine vessel radius by contracting and relaxing
• Secrete an extracellular matrix which gives vessels their elastic properties
• Can multiply in some diseases

Question 6

Why is elasticity important in vascular smooth muscle?

Answer 6

To allow large arteries to act as a pressure resevoir.

Prevents pressure falling to 0 as blood leaves arteries during diastole.

Question 7

What is an example of a clinical defect in vascular smooth muscle?

Answer 7

-Calcification in human artery; caused by healing response to the presence of dead cells. Reduces elasticity of vessel- BP affected.
Age also reduces elasticity of vessel.

Question 8

In what area of arteries and veins is elastin and collagen type III?

Answer 8

They have a tunica externa level composed of elastin and collagen type III.

Question 9

What is blood pressure?

Answer 9

Circulation of fluid contained within a space of definite volume.

Question 10

When does blood pressure fall during circulation?

Answer 10

Pressure falls as blood circulates from left ventricle to right ventricle (systemic circulation).
And right ventricle to the left ventricle (pulmonary circulation).

Question 11

What do we need to supply our basic metabolic demands in terms of blood?

Answer 11

We require a certain volume/min.

Question 12

What is the normal blood pressure?

Answer 12

120/80 (systolic/diastolic)

This varies with age, environment etc.

Question 13

What unit can be used to quote blood pressure?

Answer 13

mmHg.

Question 14

What is mean arterial pressure(MAP) and how can it be calculated?

Answer 14

MAP is average pressure pushing blood round the system.
Calculated as MAP=CO X TPR (total peripheral resistance)
MAP= diastolic BP + 1/3 pulse pressure (PP)

Question 15

Which feature of aorta and arteries allow them to contain a small ammount of blood at high pressure?

Answer 15

Very thick walled/elastic

Question 16

What sort of resitance does arterioles have?

Answer 16

A variable resistance system which distributes the blood - dissipates most of the pressure.

Question 17

What sort of surface area do capillaries have?

Answer 17

Have a vast surface area where the interchange of substances with the extracellular fluid of the tissues occurs (are as little as one cell thick).

Question 18

What do the venules, veins and venae cava do?

Answer 18

A collecting and resevoir system which contains most of the blood (70%) at low pressure.

Question 19

What is the function of capillaries and the features that allow this?

Answer 19

Perform exchange of nutrients/waste products in the CV system.

• Just wide enough for erythrocyte
• One cell thick to allow rapid exchange with tissues
• Flow depends on supply from arterioles

Question 20

What factors influence transport between capillaries and tissues?

Answer 20

-The blood in the capillaries exerts a pressure on the capillary wall (hydrostatic pressure)
This tends to favour movement of fluid (small molecules) out of the capillary.
-The plasma has an intrinsic osmotic pressure due to plasma proteins (colloid pressure)
Tends to favour movement of fluid into capillary

Question 21

What happens to hydrostatic pressure and colloid pressure as blood pressure drops?

Answer 21

Hydrostatic pressure decreases

Colloid pressure will remain the same as plasma protein are too big to leave capillary.

Question 22

What is the exceptions of the pressure systems in the CV system?

Answer 22

In pulmonary system

• Pulmonary hydrostatic pressures are much lower than systemic pressure
• Colloid pressure equivalent
• Therfore have a net fluid of transfer at both ends.
• Prevents pulmonary oedema.

Question 23

What is a clinical defect that may result from pressures in the pressure system in the heart?

Answer 23

Anything that increases capillary hydrostatic pressure eg. heart failure can lead to pulmonary oedema.

Question 24

What happens to tissue fluid?

Answer 24

We dont get it all back, we have net loss.
A build up in tissues would lead to oedema.
Lymphatic system move this fluid back to blood, also responsible for moving asorbed fat into the circulation.

Question 25

Where are main baroreceptors?

Answer 25

Carotid sinus and aortic arch