Blood Vessels

Question 1

what is the purpose of the elastic recoil of arteries?

Answer 1

to convert an intermittent flow to a continuous flow

Question 2

what is the definition of elasticity?

Answer 2

reform its original shape after being stretched

Question 3

what is the definition of complicance?

Answer 3

how easy it is to stretch a material

Question 4

explain the mechanism of the wind Kessel effect?

Answer 4

systole stretches the artery walls due to the presence of elastin, and the walls being compliant
this transfers potential energy to the walls which recoil during diastole and keep the blood flow continuous, the cycle then repeats again

Question 5

what is the ratio of elastin to collagen in elastic arteries?

Answer 5

more elastin than collagen

Question 6

how do you calculate mean atrial blood pressure?

Answer 6

SP-DP/3 +DP

Question 7

what is the equation for flow?

Answer 7

flow = change in pressure / resistance

Question 8

give 5 main factors that effect blood pressure?

Answer 8

cardiac output, total peripheral resistance, elastic content of arterial walls, blood volume, blood viscosity

Question 9

what is the aortic pulse pressure?

Answer 9

the maximum increase in aortic pressure from the time the valve opens until the peak aortic pressure

Question 10

what are the main contributors of systolic pressure?

Answer 10

stroke volume, ejection velocity, arterial distensibility, diastolic pressure

Question 11

what are the main contributors of diastolic pressure?

Answer 11

total peripheral resistance, arterial elasticity, heart rate

Question 12

what are the risk factors for arteriosclerosis?

Answer 12

age (arteries lose elastin as we age), hypertension, smoking, diet

Question 13

what is arteriosclerosis?

Answer 13

walls become thickened, lose elasticity as collagen to elastin ratio increases

Question 14

what is atherosclerosis?

Answer 14

a subtype of arteriosclerosis where the walls thicken due / in conjunction with plaque build up

Question 15

what are the 3 main factors that determine blood vessel resistance?

Answer 15

tube length, blood viscosity and radius

Question 16

what effects blood viscosity?

Answer 16

haematocrit, therefore hypoxia and anaemia effect blood viscosity

Question 17

what is PAOD?

Answer 17

Peripheral arterial occlusive disease
narrowing or blockage of arteries that supply the extremities, particularly the lower limbs

Question 18

what can PAOD lead to?

Answer 18

stenosis, resulting in localised hypoxia and ischemic pain
particularly during exercise when metabolic demand can not be met

Question 19

what is lamina flow?

Answer 19

usual flow of arteries normal pattern of flow highly efficient and follows Poiseuille’s

Question 20

what is turbulent flow?

Answer 20

inefficient, high velocity flow, that is unordered doesn’t follow Poiseuille’s law

Question 21

what are the distinct histological features of large veins?

Answer 21

very thin tunica intima
moderate tunica media
extensive and large tunica adventitia containing elastin collagen and an extensive vasa vasorum
also large lumen

Question 22

where are continuous capillaries found?

Answer 22

lungs, CNS, adipose tissue

Question 23

where are fenestrated capillaries found?

Answer 23

in tissues with high exchange rates
e.g. kidneys, GI tract, endocrine glands

Question 24

where are discontinuous capillaries’ found?

Answer 24

liver, spleen, adrenal glands

Question 25

explain the structure of continuous capillaries

Answer 25

continuous layer of endothelial cells very tight junctions and a continuous basement membrane substances move between intracellular clefts (gaps between endothelial cells)

Question 26

explain the structure of fenestrated capillaries

Answer 26

as well as intracellular cleft they have 60-80nm fenestrations (holes in cells) thinner basement membrane than continuous

Question 27

explain the structure of discontinuous capillaries

Answer 27

large gaps in endothelial layer an basement membrane

Question 28

how is blood shut off to particular capillary beds?

Answer 28

pre capillary sphincters close off blood is shunted through metarteriole

Question 29

where are the receptors in the capillary for transcytosis?

Answer 29

caveola (invagination's of the lumen)

Question 30

why is starlings forces hypothesis for capillaries wrong?

Answer 30

the amount of fluid reabsorbed into the capillaries is less than expected Protein permeability studies show that capillaries are not completely impermeable to proteins Lymphatic flow is much higher than the classical hypothesis would suggest

Question 31

what are the complications of compressed tissues in oedema?

Answer 31

increased diffusion distance and extracellular fluid = slower diffusion impaired cells trafficking static fluid increases risk of infection compression of nerves can lead to pain

Question 32

what are the 4 main causes of oedema?

Answer 32

hydrostatic oedema (hypertension) oncotic oedema (loss of blood proteins e.g. loss of albumin in liver cirrhosis or more protein in interstitial fluid) permeability oedema (increase in permeability, often found in inflammation) prevention of drainage into lymph (increases interstitial hydrostatic pressure)