Fluid Shift across the capillary wall and systemic oedema Flashcards
what acts as the go between the blood and body cells?
interstitial fluid
how many layers of endothelial cells are there in capillaries?
1
f’s: capillaries
allow rapid exchange of gases, water and solutes with interstitial fluid
delivery of O2 and nutrients to the cells
removal of metabolites from cells
What is BF in capillaries dependent of?
the contractile state of the arterioles
f: terminal arterioles?
regulate regional BF to the capillary bed CB in most tissues
f: precapillary sphincters
regulate flow in a few tissues eg mesentery
why is the BF in CB v slow?
to allow time for exchange
what is formed when capillaries unite?
venules
How are exchangeable proteins moved across the capillary wall?
via vesicular transport
How do lipid soluble substances pass across the capillary wall?
via endothelial cells
How do plasma proteins move across the capillary wall?
they don’t
How do small water soluble substances pass across the capillary wall?
across pores
What does fluid movement follow?
pressure gradient
What does the movement of gases and solutes follow?
Fick’s Law of diffusion
What is transcapillary fluid flow passively driven by?
pressure gradients across the capillary wall
d: ultra-filtration
filtration using a medium fine enough to retain colloidal particles, viruses, or large molecules
What is net filtration pressure (NFP) directly proportional to? What is the coeffient?
forces favouring filtration-forces opposing filtration Filtration coefficient (Kf)
Name the forces favouring filtration?
capillary hydrostatic pressure
interstitial fluid osmotic pressure
Name the forces opposing filtration?
capillary osmotic pressure
interstitial fluid hydrostatic pressure
What is the equation for NFP?
(PC + pi i)-(pi C + Pi)
What can be concluded from NFP quation?
starling forces favour filtration at arteriolar end, reabsorption at end of venular end
What is the general name given for the forces involved in transcapillary flow?
starling forces
Name the major forces favouring filtration in systemic transcapillary flow?
Pc capillary hydrostatic pressure
Name the major forces opposing filtration in systemic transcapillary flow?
Pi C capillary osmotic pressure
How is the excess fluid returned to the circulation?
via lymph system as lymph
what is the value of pulmonary osmotic pressure?
25mmHg
what prevents accumulation of interstitial fluid?
efficient lymphatic drainage
d: oedema
Accumulation of fluid in interstitial space
what is the effect of oedema in the lungs?
diffusion distance increases gas exchange is therefore compromised
Name the causes of oedema
raised capillary pressure
reduced plasma osmotic pressure
lympathetic insufficiency
changes in capillary permeability
How does raised capillary pressure occur?
arteriolar dilatation
raised venous pressure
What is the effect of left ventricular failure?
pulmonary oedema
What is the effect of right ventricular failure?
peripheral oedema, ankle/ sacral
If you have a oedema and stand for a long time what can be caused?
swollen ankles
How does reduced plasma osmotic pressure occur?
Normal [plasma protein]p = 65-80 g/l Oedema if < ~ 30 g/l normal plasma protein falls if malnurished proetin malabsorption XS renal excretion of protein hepatic failure
how does lymphatic insufficiency occur?
lymph node damage filariasis-elephantiasis
How do changes in capillary permeability occur?
inflammation
histamine increases leakage of protein
what is a clinical sign of pulmonary oedema?
breathlessness
On examination how will pulmonary oedema be manifested?
crepitations in auscultation of lung bases
How will pulmonary oedema be demonstrated in CXR?
haziness in perihilar region
