Exchange and the Lymphatic System

Question 1

How are capillaries specialised for exchange

Answer 1

Lots of them
Thin walled - diffusion barrier
Small diameter - large area:volume ratio

Question 2

Continuous capillaries

Answer 2

Have no clefts or pores or only clefts

Question 3

Fenestrated capillaries

Answer 3

Have clefts and pores

Question 4

Discontinuous capillaries

Answer 4

Clefts and massive pores

Question 5

By what methods to capillaries exchange material

Answer 5

Diffusion and carrier-mediated transport (blood-brain barrier)

Question 6

Diffusion in capillaries

Answer 6

Self-regulating
Non-saturable
Non-polar substances across membrane
Polar substances through clefts/channels

Question 7

Bulk-flow

Answer 7

Mass exchange of fluid

Question 8

Effect of hydrostatic pressure in capillaries

Answer 8

Pushes fluid through the leaky capillaries, building up an osmotic (oncotic) pressure

Question 9

Effect of osmotic (oncotic) pressure in capillaries

Answer 9

Draws fluid back into capillaries

Question 10

Starlings forces

Answer 10

Balance of hydrostatic and osmotic pressures

Question 11

Volume of fluid lost from capillaries per day

Answer 11

20L

Question 12

Volume of fluid regained in capillaries per day

Answer 12

17L

Question 13

Remaining fluid in capillaries

Answer 13

3L

Question 14

The excess fluid is drained via

Answer 14

The lymphatic system

Question 15

Oedema

Answer 15

Accumulation of excess fluid

Question 16

Causes of oedema

Answer 16

Lymphatic obstruction
Raised central venous pressure (CVP)
Hypoproteimemia
Increased capillary permeability

Question 17

How can resistance of vessels be controlled

Answer 17

By changing the radius

Question 18

Resistance vessels are the

Answer 18

Arterioles

Question 19

Arteriolar radius affects

Answer 19

Peripheral blood flow and total peripheral resistance so MAP

Question 20

Fundamental equation of cardiovascular physiology

Answer 20

MAP = CO x TPR

Question 21

Mean arterial pressure is important as it

Answer 21

Provides the driving force that pushes blood through useful places in the body

Question 22

Darcy’s law

Answer 22

Flow = ΔPressure/Resistance

Question 23

Intrinsic mechanisms

Answer 23

Concerned with meeting the selfish needs of each individual tissue

Question 24

Extrinsic mechanisms

Answer 24

Concerned with ensuring that the TPR and so MAP of the whole body stay in the right ball park

Question 25

Extrinsic control via sympathetic nerves

Answer 25

Release noradrenaline, binds to alpha1 receptors, causes arteriolar constriction, decreases flow through that tissue and increases TPR increasing MAP

Question 26

Extrinsic control via parasympathetic nerves

Answer 26

Usually no effect

Question 27

Extrinsic control of most tissues via hormones

Answer 27

Adrenaline released from adrenal medulla, binds to alpha1 receptors, causes arteriolar constriction, decreases flow and increases TPR so MAP

Question 28

Extrinsic control of skeletal and cardiac muscle via hormones

Answer 28

Adrenaline released from adrenal medulla, binds to beta2 receptors, arteriolar dilation, increases flow and decreases TPR so MAP

Question 29

Active (metabolic) hyperaemia is a result of

Answer 29

A build up of metabolites in blood vessels

Question 30

Intrinsic control via active (metabolic) hyperaemia

Answer 30

Release of EDRF/NO, arteriolar dilation, increase flow to wash out metabolites

Question 31

EDRF and NO are

Answer 31

Paracrines

Question 32

Pressure (flow) autoregulation is a result of

Answer 32

A decrease in MAP which causes a decrease in flow causing metabolites to accumulate

Question 33

Intrinsic control via pressure (flow) autoregulation

Answer 33

Release of EDRF/NO, arteriolar dilation, flow restored to normal

Question 34

Intrinsic control via reactive hyperaemia

Answer 34

Obstruction of blood supply causes a subsequent increase in blood flow

Question 35

Intrinsic control via the injury response

Answer 35

Mast cells release histamine, causes arteriolar dilation, increased blood flow and permeability

Question 36

Aim of the injury response

Answer 36

To aid delivery of blood born leucocytes etc to injured area

Question 37

Specialised coronary circulation

Answer 37

Blood supply is interrupted by systole, excellent hyperaemia and expression of many beta2 receptors swamp any sympathetic arteriolar constriction

Question 38

Specialised cerebral circulation

Answer 38

Needs to be kept stable, shows excellent pressure autoregulation

Question 39

Specialised pulmonary circulation

Answer 39

Decrease on oxygen causes arteriolar constriction which is opposite to most tissues, ensured blood directed to best ventilated parts of lungs

Question 40

Specialised renal circulation

Answer 40

Main function is filtration which depends on pressure so MAP would have big effects on blood volume, shows excellent pressure autoregulation