Flashcards in Fluid shift across the Capillary Wall Deck (40)
What do precapillary sphincters in capillaries do?
Regulate flow in few tissues (e.g. mesentery)
What do capillaries unite to form?
What is the speed of blood flow through capillary beds?
Slow to allow time for exchange
In relation to transport across capillary walls, how do lipid-soluble substances pass through?
The endothelial cells
In relation to transport across capillary walls, how do small, water-soluble substances pass?
Through the pores
In relation to transport across capillary walls, how are exchangable proteins moved?
Across the endothelial cells by vesicular transport
What substances generally, cannot cross the capillary wall?
In relation to transport across the capillary wall, what does fluid movement follow?
Pressure gradient (bulk flow)
What is transcapillary flow passively driven by?
Pressure gradients across the capillary wall
What si ultra-filtration?
What is exchange across the capillary wall of essentially protein free plasma?
What is Net Filtration Pressure proportional to?
Forces favouring filtration - forces opposing filtration
What also affects net fluid filtration?
A filtration coefficient
What are forces called that are involved in transcapillary fluid flow?
Give two forces favouring filtration?
1. Capillary hydrostatic pressure
2. Pi(i) - interstitial fluid osmotic pressure
Give two forces opposing filtration?
1. Pi(c) - capillary osmotic pressure
2. Pe - interstitial fluid hydrostatic pressure
What is the equation for NFP?
NFP = (PC +Pi(i)) - (PiC + Pi)
Give the value of Capillary hydrostatic pressure (Pc) in arterioles and venules?
35 mmHg - arterioles
17 mmHg - venules
Give the value of Intersitital fluid osmotic pressure Pi(i)?
Give the value for capillary osmotic pressure Pi(c)?
Give the value for interstitial fluid hydrostatic pressure (Pi)
Give the equation for NFP arteriolar end ?
NFP arteriolar end = (35 + 1) - (25 + 1) = +10 mmHgq
What is the equation for NFP venular end?
NFP venular end = (17 + 1) - (25 + 1) = -8 mmHg
What do Starling forces favour?
Favour filtration at arteriolar end, reabsorption at venular end
Name forces favouring filtration, in major forces involved in systemic transcapillary fluid flow?
Pc - Capillary hydrostatic pressure (35 mmHg arterioles, 17 mmHg veules)
Name forces opposing filtration, in major forces involved in systemic transcapillary fluid flow?
Pi(c) - capillary osmotic pressure (25 mmHg)
During a day what exceeds reabsoprtion by 2 - 4 litres?
What happens to hte excess fluid after a days filtration exceeding reabsorption?
Returned to the circulation via the lymphatics as lymph
In the pulmonary capillaries, what is the osmotic pressure?
What increases the diffusion distance and compromises gas exchange?
What are two factors making up raised capillary pressure, which is a cause of oedema?
1. Arteriolar dilatation
2. Raised venous pressure
What does left ventricular failrue cause?
What does right ventricualr failure cause?
What way does heart failure shift the Frank-Starling curve?
To the right
What is a cause of oedema, relating to plasma osmotic pressure?
Reduced plasma osmotoic poressure
What is the value of normal plasma protein, and what is the value of occuring oedema?
65 - 80 g/l
Give two factors of lymphatic insufficiency in causing oedema?
1. Lymph node damage
2. Filariasis - elephantiasis
Give two factors which could lead to changes in capillary permeability, causing oedema?
Histamine increases leakage of protein
Where can pitting oedema occur?
Ankles and sacrum