Capillaries II Flashcards
Fluid exchange
How is hydrostatic pressure exerted? [2 marks]
- Fluid moves across membrane to interstitial space
- Due to blood flow
How is osmotic pressure exerted? [2 marks]
- Fluid moves into capillaries
- Due to plasma proteins
What is Πp and Πi? [2 marks]
Πp = osmotic pressure due to plasma proteins Πi = osmotic pressure due to interstitial proteins
What is Pc and Pi? [2 marks]
Pc = hydrostatic pressure due to capillary blood pressure Pi = hydrostatic pressure due to capillary blood
What does Jv mean? [1 mark]
Movement of fluid (flux)
What does Lp mean? [1 mark]
Hydraulic conductance of endothelium i.e. how leaky it is to fluid
What does σ mean? [2 marks]
Reflection coefficient i.e. fraction of osmotic pressure that is exerted
σ = 1 = reflected
σ = 0 = leaks out
What are Lp and A in normal conditions? [1 mark]
CONSTANT
What happens to hydrostatic pressure as you go down a capillary? [1 mark]
Decreases
What happens to osmotic pressure as you go down a capillary? [1 mark]
Nothing
What can excess filtration be caused by? [2 marks]
- Decreased osmotic pressure
- Increased hydrostatic pressure
What does control of extracellular fluid balance depend on? [3 marks]
- Capillary filtration
- Capillary reabsorption
- Lymphatic system
Which Starling factors determine change in fluid balance? [3 marks]
- Circulation
- Interstitial fluid
- Lymphatic system
What happens to osmotic pressure in hypovolemia? [1 mark]
Nothing
What happens to hydrostatic pressure in hypovolemia? [1 mark]
Decreases
What happens to cardiac output in hypovolemia and what happens next? [2 marks]
- Decreases
- Causes BP to decrease (BP = CO x TPR)
How is hypovolemia restored? [4 marks]
- Sympathetic vasoconstriction
- Reabsorption of fluid
- Higher CO
- Higher BP
What are the causes of oedema? [4 marks]
- Increased Pc (due to increased pressure at venous end)
- Decreased πp (due to less albumin)
- Inflammatory response (leady capillaries)
- Lymphatic problems (e.g. elephantitis and lymphoedema)
Which clinical scenarios can cause increased capillary pressure? [3 marks]
- Dependent (gravitational) oedema
- DVT
- Heart failure
Which clinical scenarios can cause decreased plasma osmotic pressure? [3 marks]
- Malnutrition/malabsorption
- Nephrotic syndrome (loss of urinary protein)
- Liver disease (less albumin made)
