Week 1 - The Peripheral Circulation

Question 1

What does the peripheral circulation include?

Answer 1

capillaries, arterioles, lymphatic system and oedema

Question 2

How far is every tissue from a capillary?

Answer 2

100 micrometres

Question 3

What are 3 types of capillary?

Answer 3

continuous, fenestrated and sinusoid/discontinuous

Question 4

Where would you find a continuous capillary and what’s its structure?

Answer 4

blood brain barrier. tight junctions present so nothing gets through

Question 5

Where would you find a fenestrated capillary and what’s its structure?

Answer 5

• kidney. allows macromolecules to pass through transcytosis, via pores/vesicles or fused vesicles, forming temporary channels. clefts too.
• GI tract

Question 6

Where would you find a sinusoid/discontinuous capillary and what’s its structure?

Answer 6

• liver. large gaps in endothelium as well as clefts and pores. for large proteins
• lymph nodes
• spleen
• bone marrow
• adrenal glands

Question 7

When would you need carrier mediated transport in epithelium?

Answer 7

in the brain as a glucose transporter

Question 8

How does exchange occur in the capillaries? How much fluid?

Answer 8

bulk flow. ion conc. hydrostatic pressure pushes fluid out and osmotic/oncotic pressure drags it back in. 20L pushed out and 17L pulled in daily.

Question 9

What is the difference between capillaries and lymphatic capillaries?

Answer 9

similar structure but lymph have nodes and are blind ended, and have valves

Question 10

How does lymphatic system function?

Answer 10

fluid drains into nodes, then into larger lymphatic vessels, making its way back to the heart and draining via vena cava back into CVS/

Question 11

How does oedema occur? (4 ways)

Answer 11

• CVS isnt functioning, hydrostatic pressure increases, pushing more water out which accumulates in ISF.
• parasite like worm in lymph node, blocking drainage
• autoimmune disorder causing inflammation, which causes permeable capillaries - fluid loss
• hypoproteinaemia

Question 12

What is darcy’s law?

Answer 12

flow = change in pressure/resistance

Question 13

How does changing the arterial radius/resistance affect MAP?

Answer 13

more resistant decreases flow and thus decreases MAP.

Question 14

What is active/metabolic hyperaemia?

Answer 14

when exercising, more metabolites produces and need to diffuse into blood. so more blood is needed to create steady state. endothelium releases EDRF or NO, which causes arteriole to dilate, increasing flow, decreasing resistance.

Question 15

What are local vs central controls?

Answer 15

local controls meet the needs of selfish tissues. central controls ensure total peripheral resistance is maintained.

Question 16

What is pressure/flow autoregulation?

Answer 16

somehow mean arterial pressure is reduced. this means metabolites arent being washed away. so endothelium releases EDRF and NO to cause arteriolar dilatation and increase flow. this increases MAP

Question 17

what are the local controls of mean arterial pressure? (4)

Answer 17

• active/metabolic hyperaemia,
• pressure/flow autoregulation,
• reactive hyperaemia,
• the injury response

Question 18

What is reactive hyperaemia?

Answer 18

if blood supply is cut, e.g. by sphygmomanometer, metabolites build up and vessels dilate, so when blood is reintroduced, it flows so fast

Question 19

What is the injury response?

Answer 19

injuring part of body triggers inflammation. e.g. stubbing toe causes calor, rubor, dolor and tumor

Question 20

What are the central controls maintaining TPR (total peripheral resistance)? (3)

Answer 20

• sympathetic releases noradrenaline, binding to a1 receptors, constricting vessels, increasing TPR and MAP
• parasympathetic dont innervate vessels except genitalia and salivary glands
• adrenaline activates a1 receptors and b2 receptors dilate smooth muscle and increases contractillity. counterracted.

Question 21

What are 4 special regions of the body with mechanisms to adapt to MAP quickly?

Answer 21

coronary circulation, cerebral circulation, pulmonary circulation, renal circulation

Question 22

How is the cerebral circulation specialised?

Answer 22

has great pressure auto regulation. if MAP falls, arterioles dilate to maintain perfusion. brain NEEDS to be kept perfused

Question 23

How is the coronary circulation specialised? 2 ways

Answer 23

• heart has excellent hyperaemia. responds quickly to v small changes in metabolite conc.
• heart has many b2 receptors so smooth muscle can relax and arterioles dilate

Question 24

How is the pulmonary circulation specialised?

Answer 24

decrease in PaO2 causes arteriolar constriction, to fix ventilation-perfusion imbalance so deoxygenated blood doesnt return to the heart. called shunt.

Question 25

How is the renal circulation specialised?

Answer 25

excellent pressure autoregulation. glomeruli are protected from high pressure, which can cause kidney damage.

Question 26

What is endothelin?

Answer 26

most potent and longest lasting vasoconstrictor