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THE PATIENT PHYSIOLOGY EXAM > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

What is microcirculation?

A

Blood flow through the smallest vessels involves capillaries and lymphatic vessels
Transport of nutrients and removal of waste

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2
Q

What are the blood vessels involved in microcirculation from the smallest to the largest?

A 
Vena cava
Aorta
small veins
small arteries
arterioles
venules
capillaries
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3
Q

What is the structure of capillaries?

A

single layer of highly permeable endothelial cells
has pores that allow diffusion
 SA= 500-700m2
 Thin walls
 Modest volume- 5% of body’s blood
 Large cross sectional area amongst all the vessels
 Slowest flow velocity- 2cm/min or 0.3mm/s

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4
Q

Why is blood flow slowest in capillaries?

A

so more time for gas and nutrient exchange

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5
Q

What is the role of the capillaries?

A

allow exchanging of solutes and fluid between plasma and interstitial fluid

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6
Q

What is starling’s law of filtration?

A

A law that governs the flow of filtration across the capillaries

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7
Q

What 4 parameters are in the starling equation?

A

Pc= capillary hydrostatic pressure
Pi= interstitial fluid hydrostatic pressure
Pi c= capillary plasma oncotic pressure
Pi i= interstitial fluid oncotic pressure

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8
Q

What does the K in Starling’s equation represent?

A

Filtration coefficient

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9
Q

What is the movement of H2O from plasma to interstitial space called?

A

filtration

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10
Q

What is the movement of H20 from interstitial space to plasma called?

A

absorption

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11
Q

What determines the net flow of fluid across a capillary?

A

The balance of the 4 starling forces

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12
Q

Why is the osmotic effect of capillary fluid greater than the osmotic effect of the interstitial fluid?

A

the capillary fluid/plasma contains more proteins which generates a higher colloid osmotic pressure and attracts more water via osmosis

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13
Q

What is colloid osmotic pressure?

A

osmotic pressure by proteins in blood plasma or interstitial fluid

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14
Q

What solutes move across capillary wall by simple diffusion?

A

O2, CO2, nutrients and metabolites

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15
Q

What 2 pathways do the solutes use to move between blood and interstitial fluid?

A

transcellular

paracellular

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16
Q

What is transcellular movement?

A

simple diffusion through endothelial cells

17
Q

What is paracellular movement?

A

simple diffusion through tight junctions or gaps of endothelial cells

18
Q

What are the types of transcellular movement?

A

simple diffusion
facilitated diffusion
transcytosis

19
Q

What are the 3 types of capillary structures?

A

continuous
fenestrated
discontinuous/sinusoid

20
Q

Describe the structure of a continuous capillary?

A

endothelial cells tightly held together
tight junctions between cells
continuous basement membrane
presence of intracellular clefts

21
Q

What types of molecules pass through continuous capillary and what route do they use?

A

small molecules- water, ions

use paracellular route via intercellular clefts

22
Q

Describe the structure of a fenestrated capillary?

A

small openings in the cells

leaky

23
Q

What route is used to cross fenestrated capillaries?

A

use fenestrations and intracellular cleft

24
Q

Describe the structure of a discontinuous/sinusoid capillary?

A 
very leaky
endothelial cells held very loosely 
large gaps between cells 
holes in the basement membrane
large intracellular gaps
25
Q

What route is used to cross discontinuous/sinusoid capillaries?

A

cross through the holes in membrane and intracellular gasp

26
Q

What is the lymphatic systems role?

A

scavenger system
Drains excess fluid, water, ions, glucose, lipid, WBC, protein, large particles and debris from interstitial space back into blood

27
Q

What is the fluid collected from interstitial space called?

A

lymph

28
Q

What are lymphatic vessels?

A

smooth muscle

29
Q

What is the role of the lymph nodes surrounding the lymphatic vessels?

A

immune function- they have lymphocytes which destroy foreign particles and bacteria present in the lymph

30
Q

What allows the one way flow of lymph from tissues to veins?

A

lymphatic valves

31
Q

Where is lymph collected from?

A

All body tissue except brain

32
Q

What are lymphatic ducts?

A

sites at which lymph empties into large veins

33
Q

What is oedema?

A
  • Swelling caused by excess fluid in tissues/interstitial space
  • Swelling of skin after damage to local capillaries
34
Q

What causes oedema?

A

High hydrostatic capillary pressure due to HF, blood clot, cardiac failure, deep vein thrombosis
imbalance of starling forces
Low blood/plasma protein due to liver failure, poor nutrition and burns
Lymphatic failure due to damaged lymphatic vessels, infected lymph nodes, protein accumulated in undrained fluid?

35
Q

What is lymphoedema?

A

accumulation of lymph which obstructs lymph system

36
Q

What cause can lead to peripheral and pulmonary oedema?

A

HF

37
Q

Describe the MOA of peripheral oedema?

A
  1. Left ventricle dysfunction= abnormal CO
  2. MAP falls due to small CO
  3. Reflexes triggered to restore MAP- baroreceptors, salt and water retention by kidneys
  4. Salt and water retained
  5. Plasma vol increases
  6. Venous pressure increases
  7. Capillary pressure increases
  8. Filtration increases
  9. Fluid lot from capillaries to tissue= swelling
38
Q

Describe the MOA of pulmonary oedema?

A
  1. Left ventricular dysfunction
  2. Reduced ejection which means reduced SV and CO- so blood is left behind instead of ejected
  3. Blood backed up into left atrium
  4. Blood build up in pul veins which return blood to heart
  5. Pul veins are engorged and swell due to lots of blood and hydrostatic pressure increases
  6. Pul capillary pressure increases
  7. Increased filtration
  8. Fluid leaves capillaries and accumulates in interstitial space of lungs

THE PATIENT PHYSIOLOGY EXAM (2 decks)

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