lecture 4 Flashcards
What are the three types of capillaries?
Continuous, fenestrated and discontinuous
What are the continuous caplillaries?
The endothelial cells in the intima are linked by tight junctions so that transport has to occur through calveoli or intracellular clefts
What are fenestrated capillaries?
Fenestrated capillaries have a more porous structure. the fenestra have a greater permeability so substances can pass through more easily (10x more permeable than continuous capillaries)
What are discontinuous capillaries?
Discontinuous capillaries have large gaps between adjacent endothelial cells so that large proteins can pass through
Where do continuous capillaries occur?
Fat, muscle and nervous system
Where do fenestrated capillaries occur?
In intestinal villi, endocrine glands and kidney glomeruli
Where do discontinuous capillaries occur?
liver, bone marrow and the spleen
What is another name for discontinuous capillaries?
Sinusoids
What is the hydrostatic pressure?
Pressure a fluid exerts when in a confined space
What is the osmotic pressure
Pressure caused by a difference in concentration of two fluids that have been separated by a semi-permeable membrane
What is the hydrostatic pressure like between a vessel and the ISS
The ISS has a lower pressure than the vessel of 1mmHG and so arterial fluid tends to move out of the vessel.
At the arteriole end the pressure in the vessel is at 35mmHg creating a difference of 34mmHg.
At the venule end the pressure is 15mmHg, creating a difference of 14mmHg.
Therefore there is a greater tendency for fluid to more out from the arterial end into the ISS than the venule end
What is the osmotic pressure like between the vessel and ISS
Blood contains a larger amount of proteins relative to the ISS (25mmHg), so there is a tendency for fluid to move into the vessel from the ISS (3mmHg) (difference of 22mmHg)
What does the relationship between the hydrostatic pressure and osmotic pressure show?
Fluid balances between the hydrostatic and osmotic pressure.
At the arterial end the difference between the hydrostatic and osmotic pressure of 12mmHg means fluid moves out (hydrostatic > osmotic = fluid out
And at the venule end the difference between the hydrostatic and osmotic pressure of -8mmHg means fluid moves in (osmotic >hydrostatic = fluid in)
What does the lymphatic system do?
Role in regulating homeostasis, takes fluid from ISS back to venous system if there is too much fluid
