Exchange And The Lymphatic System

Question 1

How close is every tissue to a capillary

Answer 1

100um

Question 2

Continuous capillaries

Answer 2

No clefts or pores eg the brain

Or only clefts eg muscle

Question 3

Fenestrated capillaries

Answer 3

Clefts and pores eg intestine

Question 4

Discontinuous capillaries

Answer 4

Clefts and massive pores eg liver

Question 5

Facts about diffusion

Answer 5

Self regulating
Non saturable
Non polar can cross
Polar go through clefts or channels

Question 6

Carrier mediated transport in capillaries example

Answer 6

Glucose transporter

Question 7

What does hydrostatic pressure do

Answer 7

Forces fluid out of capillaries

Question 8

What does osmotic (oncotic) pressure do

Answer 8

Forces fluid out of capillaries

Question 9

How much fluid is lost and gained each day in capillaries

Answer 9

20L lost and 17L gained

The remainder is collected by lymph system

Question 10

Causes of oedema

Answer 10

Lymphatic obstruction eg surgery
Raised CVP eg ventricular failure
Hypoproteinemia eg nephrosis, liver failure, nutrition
Increased capillary permeability eg inflammation

Question 11

Equation for Mean Arterial Pressure

Answer 11

MAP=COxTPR

Difference in pressure = flow X resistance
And CVP is negligible

Question 12

How is blood flow to each vascular bed kept sufficient and keep mean arterial pressure right

Answer 12

Two levels of control over smooth muscle surrounding arterioles
Intrinsic and extrinsic

Question 13

Extrinsic (neural) control of smooth muscles on arterioles

Answer 13

Sympathetic releases noradrenaline which binds to a1 and causes arteriolar constriction, decreasing flow through that tissue and increasing TPR

parasympathetic does not much

Question 14

Extrinsic (hormonal) control of smooth muscles around arterioles

Answer 14

Adrenaline is released from the adrenal medulla and binds to a1 receptors causing arteriolar constriction

BUT in skeletal and cardiac muscles it also activates b2 receptors causing vasodilation (redirection of blood in fight or flight)

Question 15

Other hormones released in response to low blood volume

Answer 15

Angiotensin and vasopressin

Question 15

Other hormones released in response to low blood volume

Answer 15

Angiotensin and vasopressin

Question 16

Other hormone produced in response to high blood volume

Answer 16

Atrial natriuretic factor

Question 17

Local (Intrinsic) controls of smooth muscle surrounding arterioles

Answer 17

Active hyperaemia
Pressure autoregulation
Reactive hyperaemia

Question 18

Cause and response to active (metabolic) hyperaemia to control peripheral blood flow

Answer 18

More metabolic activity causes an increase in metabolite concentration (CO2, H+, K+) which causes a release of EDFR (NO)

This causes arteriolar dilation and the increased flow washes out metabolites

Question 19

Pressure (flow) autoregulation

Answer 19

A decrease in MAP causes decreased flow

Metabolites accumulate and NO is released so the arterioles dilate and flow returns to normal

Question 20

Reactive hyperaemia

Answer 20

Occlusion of blood supply causes a subsequent increase in blood flow (extreme version of pressure autoregulation)

Question 21

Injury response

Answer 21

C fibre releases substance P and mast cells produce histamine

The increase in blood flow due to arteriolar dilation and the increase in permeability aids delivery of leukocytes etc to injured area

Question 22

Coronary circulation flow characteristics

Answer 22

Blood supply is interrupted by systole but still has to cope with increased demand during exercise

Shows excellent hyperaemia (can dilate to have lots of blood)
n d lots of B2 receptors that swamp the sympathetic arteriolar constriction\\

Question 23

Cerebral circulation

Answer 23

Needs to be kept very stable so shows excellent pressure autoregulation

Question 24

Pulmonary circulation

Answer 24

Decrease in O2 causes arteriolar constriction (opposite to normal) so blood is directed to the best ventilated parts of the lung

Question 25

Renal circulation

Answer 25

The main function is filtration which depends on pressure and so changes in MAP would have big effects
Therefore shows excellent pressure autoregulation