microcirculation

Question 1

what is the oncotic pressure generated by the plasma proteins of the capillaries?

Answer 1

28mmHg

Question 2

what are the main plasma proteins?

Answer 2

albumin

Question 3

what way does water flow into/out of the capillaries by oncotoc force?

Answer 3

into the capillaries

Question 4

what is the interstitial oncotic pressure?

Answer 4

5-8mmHg

Question 5

what is the hydrostatic pressure?

Answer 5

the pressure generated on the vessel wall by the flow of blood

Question 6

what is the hydrostatic pressure at the arterial end of the capillaries?

Answer 6

30-40mmHg

Question 7

what is the hydrostatic pressure at the venous end of the capillaries?

Answer 7

10-15mmHg

Question 8

what does the differences in hydrostatic pressure between the capillaries and interstitial fluid result in a flow of fluid in which direction?

Answer 8

out of the capillaries

Question 9

what is the favour of direction of flow of water at the arteriole end of the capillary system?

Answer 9

flitration is favuorued (i.e. flow of fluid out of vessels)

Question 10

what is the direction of flow of fluid at the venous end of the capillary system?

Answer 10

absorption is favoured (i.e. flow of fluid back into the vessels)

Question 11

how much water do capillaries lose per day?

Answer 11

2-3 litres

Question 12

what is the pressure in the venous system?

Answer 12

between 3-18mmHg (low pressure system)

Question 13

what percentage of blood does the venous system hold?

Answer 13

60%

Question 14

what happens when the sympathetic nervous system constricts the veins?

Answer 14

venous pressure increases, which increases venous return to the heart and in turn increases stroke volume

Question 15

inspiratory movements cause an increase in venous return too. how do they do this?

Answer 15

• diaphragm descends and increases abdominal pressure and therefore pressure in abdominal veins
• the pressure in the thorax decreases and therefore the pressure in the intrathoracic veins and right atrium decreases too. This results in an overall pressure difference between the peripheral veins and the heart

Question 16

what postural changes cause around 500ml of blood to move fro the upper body to the legs?

Answer 16

the effect of going form supine to upright

Question 17

what happens to venous return, cardiac output and blood pressure when this happens?

Answer 17

they decrease

Question 18

what happens to counteract the sudden decrease in blood pressure caused by postural changes?

Answer 18

reflex vasoconstriction in legs and lower abdomen