Arteries veins and control of PVR

Question 1

what does PVR stand for

Answer 1

peripheral vascular resistance
(resistance to blood flow)

Question 2

types of blood vessels

Answer 2

large arteries
arterioles
capillaries
venules
veins
- structure adapted for their role

Question 3

where are endothelial cells

Answer 3

line all vessels and the inside of the heart chambers

Question 4

what is the role of endothelial cells

Answer 4

important for local blood pressure control
prevent platelet aggregation and blood clot formation
angiogenesis + remodelling
permeability barrier for nutrients/ fluid between plasma and interstitial fluid

Question 5

where are vascular smooth muscles

Answer 5

present in all vessels (not in smallest capillaries)

Question 6

what is the role of vascular smooth muscles

Answer 6

determine vessel radius by contracting/ relaxing
secrete and extracellular matrix which gives the vessels their elastic properties
can multiply in some diseases - e.g. hypertension

Question 7

what is arterial elasticity

Answer 7

compliancy of arterial tissue/ vessels
- declines with age and in some diseases (can raise blood pressure)

Question 8

what does arterial elasticity prevent

Answer 8

BP falling to 0 as blood leaves arteries during diastole

Question 9

clinical relevance of arterial elasticity

Answer 9

calcification in human artery - caused by a healing response to the presence of ‘dead’ cells
reduces elasticity of the vessel - BP affected

Question 10

between which ventricles of the heart does BP fall around the body

Answer 10

LV -> RV (systemic circulation)
RV -> LV (pulmonary circulation)
- blood moves down a pressure gradient

Question 11

what is normal BP

Answer 11

120/80 (systolic/ diastolic) - varies with age, environment
- 120 = LV

Question 12

what is MAP and how is it calculated

Answer 12

MAP is the average pressure pushing blood round the system
MAP = CO x PTR
- normally quoted as mmHg than SI unit of Pa (1N/m2)
- MAP of 90mmHg is measured above atmospheric pressure

Question 13

what creates arterial BP

Answer 13

blood forcefully ejected into the arteries from the Vs
elastic artery wall stretched out by pressure
increasingly small vessels maintain high pressure (+ resistance to flow)

Question 14

aorta/ arteries structure/ function

Answer 14

contain a small amount of blood at high pressure
very thick walled/ elastic

Question 15

arterioles structure/ function

Answer 15

a variable resistance system which distributes blood
dissipate most of the pressure

Question 16

capillaries structure/ function

Answer 16

vast SA where interchange of substances w/ extracellular fluid of the tissues occurs

Question 17

venules, veins and vena cavae structure/ function

Answer 17

a collecting and reservoir system which contain most of the blood (70%) at low pressure
very distensible

Question 18

adaptation of capillaries

Answer 18

1 cell thick for rapid exchange with tissues
just wide enough for erythrocytes to squeeze through -> more SA

Question 19

what is hydrostatic pressure

Answer 19

blood in capillaries exerting pressure on the capillary wall
- tends to favour movement of fluid out of the capillary
- will decrease as BP drops (arteries -> venous)

Question 20

what is colloid pressure

Answer 20

plasma has an intrinsic osmotic pressure due to plasma proteins
- tends to favour movement of fluid into the capillary
- remains the same (arteries -> venous) as plasma proteins are too big to leave the capillary
- 28mmHg inside arteriole, 3mmHg on the outside

Question 21

what is the movement of fluid across arteries -> venous

Answer 21

moves out at the arterial end as hydrostatic pressure is ^ (35mmHg)
moves into the venous end as hydrostatic pressure is decreased (15mmHg)

Question 22

how is movement of fluid different in the pulmonary system and how is it important

Answer 22

pulmonary hydrostatic pressures are much lower than systemic pressure
colloid pressure remains equivalent
therefore -> net fluid transfer at both ends
this prevents pulmonary oedema

Question 23

what is pulmonary thrombosis

Answer 23

blood into alveoli, decreases gas change efficiency/ ability
clot causes build-up of pressure in capillary

Question 24

clinical relevance of fluid movement

Answer 24

in HF, capillary hydrostatic pressure ^ particularly in extremities
pitting oedema
pulmonary oedema caused by: high altitude (HAPE) or LH failure
RH failure - jugular distension

Question 25

drug therapies to ‘unload’ the heart

Answer 25

nitrate, ACE inhibitors, vasodilators