Exchange and the lymphatic system Flashcards
Where do the leaks occur in continuous capillaries?
-Leaky junctions
Where can continuous capillaries with no clefts be found?
Brain
Where can continuous capillaries with leaky clefts be found?
Muscle (lots of other tissues)
Where can fenestrated capillaries be found?
Intestine
What are fenestrated capillaries specialised for?
Fluid exchange
Where can discontinuous capillaries be found?
Liver
Why are discontinuous capillaries found in liver?
Lots of proteins made in liver need to get to blood stream
What are the two parts of a clot?
- Platelet plug
- Fibrin clot
Why is blood flowing through capillaries at risk of clotting?
Because its super slow
What is the basement membrane made of?
-Collagen
What happens to platelets when they come into contact with the basement membrane?
-Form a plug
What does fibrinogen turn into when clotting?
Fibrin
What converts Fibrinogen to fibrin?
-Thrombin
How does endothelium stop clotting?
-Acts as a physical barrier between collagen and platelet
What does the endothelium produce to stop clotting and how?
- Prostacyclin and NO
- Tissue factor pathway inhibitor
What does prostacylin and NO?
-Inhibit platelet aggregation
What does TFPI
-Stops thrombin & inactivates it
What does endothelium produce to prevent clotting?
- Thrombomodulin
- Heparin
What does thrombomodulin do?
-Binds to thrombin & inactivates it
What does heparin do?
-Innactivates thrombin
What does endothelium produce to digest clot?
Plasminogen activator (t-PA)
What does plasmin do?
Converts fibrin to fibrinogen?
What are the characteristics of diffusion? (4) between capillary-ECF-cell
- Self-regulating
- non-saturable
- Non-polar substances across membrane
- Polar substances through clefts/channels
What requires carrier mediated transport?
-Glucose trasnporter
What does non saturable mean in relation to diffusion?
-No Max speed (Unlike a set number of protein pumps)
What two forces control bulk flow?
- Hydrostatic pressure
- Osmotic (oncotic) pressure
How much plasma is lost due to hydro static forces?
-20L
How much plasma is regained by oncotic pressure?
17L
How much fluid does lymph move a day?
-3L (blind ended pumps)
What is Oedema?
Accumulation of excess fluid
When does oedema happen? (4 points)
- Lymphatic obstruction
- Raised CVP
- Hypoproteinemia
- Increased capillary permeability
How can lymphatic obstruction come about?
- Filariasis (Tropical disease caused by parastic worms)
- Surgery
How does raised CVP come about?
due to ventricular pressure
How does hypoproteinemia come about?
Due to nephrosis, liver failure, nutrition
How does increased capillary permeability come about?
-Inflammation
EG rheumatism
What happens in swelling with a bee sting?
Increases permeability of capillaries so what and proteins are lost which reduces oncotic pressure. Permeability increased to let white t cells out
