Topic 11: Cardiovascular System - Capillary Exchange Flashcards
What is capillary exchange between?
blood and ISF
What three methods allow solutes to enter and leave capillaries?
- diffusion
- vesicular transport
- Mediated Transport
What is the role of diffusion in capillary exchange?
- major route, except for brain
Which ions and molecules can diffusion occur for in capillary exchange? (6)
- CO2
- O2
- ions
- aa
- glucose
- hormones etc
Between which cells does diffusion occur?
between endothelial cells
Which molecules is vesicular transport for?
large proteins (ie antibodies)
How does vesicular transport in capillary exchange occur? (3)
- via transcytosis
- endocytosis from blood into endothelial cell
- then exocytosis from endothelial cell into ISF
What does mediated transport require? (2)
- membrane carrier protein
- important mainly for brain
Through which mechanisms does fluid (water) enter/absorb or leave/filtrate capillaries? (2)
- osmosis
- bulk flow
Why does bulk flow allow for absorption/filtration in capillaries?
- due to pressure differences
What 4 pressures are involved in bulk flow of capillaries?
1) Blood hydrostatic pressure (BHP) - blood pressure
2) blood osmotic P (BOP) - due to plasma proteins
3) ISF hydrostatic P (IFHP) - 0 mmHg
4) ISF osmotic P (IFOP) - due to ISF proteins
Net filtration pressure (NFP) diagram
What is net filtration pressure? (2)
- sum of hydrostatic and osmotic pressures acting on the capillary
- across a capillary from arteriolar to venous end
Formula for net filtration pressure
Example given of NFP important
- negative means absorption
What occurs in the body in NFP? (3)
- 90% of filtered fluid reabsorbed to blood
-10% enters lymph - therefore ISF volume remains relatively constant
One clinical application of NFP is edema. What is edema? (20
- accumulation of fluid in the tissue (ISF)
- causes swelling
What is edema due to? (4)
1) high bp (high BHP)
2) leakage of plasma proteins into ISF, causing inflammation (increased IFOP)
3) decreased plasma proteins (malnutrition, burns) (decreased BOP)
4) obstruction of lymph vessels (elephantiasis, surgery)
