Capillary and lymphatics function

Question 1

lymphatic vessels are a series of chambers

• what seperates them
• what propels the lymph fluid movement

Answer 1

• made of myoepithelium - the epithelial cells of vessels can contract
• contains valves: free ends of the endothelial cells

At rest: 0mmHg

• when interstitial hydrostatic pressure greater than vessel hydrostatic pressure: valves forced open, fluid enters
• stretches the chambers: leads to contraction = force into next chamber

when filled: 25mmHg

skeletal muscle pump also helps to propel movement

Question 2

what is the main function of capillaries

Answer 2

1. to remove Co2 and waste from tissues

2. to deliver nutrients and O2 to tissues

Question 3

what 2 forces determines filtration of fluids OUT of and BACK in capillaries

Answer 3

1: capillary hydrostatic pressure forcing fluids out
2: Capillary oncotic pressure attracting fluids back in

Question 4

what is hydrostatic pressure and what determines it

Answer 4

1. Hyd pressure: when any vessels are stretched = pressure created

• degree of stretch determined by blood volume in the vessel
• blood volume determined by the flow of blood into the certain vessels
• the flow of blood is determined by:
  pressure gradient AND vascular resistance

Question 5

how does pre-capillary resistance affect capillary hydrostatic pressure

Answer 5

1. increase pre-capillary resistance - arteriole resistance

= reduces flow into capillary = reduces stretch = reduces hydrostatic pressure

Question 6

how does post-capillary resistance affect capillary hydrostatic pressure

Answer 6

1: increase post-cap resistance: reduces outflow from capillary bed = more trapped = increases capillary hydrostatic pressure
* reduced venous pressure (less leaves)

Question 7

how does increase arterial pressure affect capillary hydrostatic pressure

Answer 7

• increases the pressure gradient between arteriole and capillary = more blood flow into cap = increase Hyd pressure

Question 8

how does increase in venous pressure affect capillary hydrostatic pressure

Answer 8

Pv> Pc = blood back into capillary = increases hydrostatic pressure

Question 9

what is the starling’s hypothesis

Answer 9

states that there is a CONSTANT interstitial fluid volume: net filtration at arteriole end, net reabsorption at venous end of the capillary bed

Question 10

explain the starling’s hypothesis

Answer 10

1. constant capillary oncotic pressure (25mmHg)
2. arterial end: hydrostatic pressure higher than oncotic: filtration > reabsorption

but there is a gradual decline of capillary hydrostatic pressure along the length

2. venous end: oncotic pressure greater than capillary hydrostatic pressure:
   reabsorption > filtration

ideal in skin

Question 11

does starling’s law apply in kidneys and lungs? explain

Answer 11

kidneys: function : filtration:
high hydrostatic pressure in the glomerulus throughout

lungs: absorption only: ie GASES into blood
so capillary oncotic pressure is higher than hydrostatic pressure

Question 12

congestive heart failure and capillary hydrostatic pressure

Answer 12

• CHF = end systolic and diastolic volume increases: back flow into atria = into pulmonary veins (left atria)
  Left hear failure: increases pulmonary circulation pressure = pulmonary odema

right heart failure:
back flow into right atrium: pressure gradient for venous return decreases = increases systemic vein pressure
= increases Pv > Pc = capillary hydrostatic pressure increases
= odema in limbs