Exchange and Lymphatics Flashcards
What are the three types of Capillaries?
Continuous
Fenestrated
Discontinuous
Give examples of where each type of capillaries are found.
Continuous= muscle & brain(no gaps) Fenestrated= Kidney, Intestines (filtration) Discontinuous= Liver (sinusoids)
Why do clots often form in the capillaries?
The blood is very slow flowing
Which element of the capillary structure is important in preventing clotting?
The endothelium
Outline the process of clot formation
Endothelium tears, platelets detect collagen and aggregate together to form a lump. A fibrin clot forms on top of this. Thrombin stimulates the conversion of fibrinogen to fibrin.
How does the Endothelium prevent clot formation?
- Physical barrier between collagen and platelets.
- Stop platelet aggregation- prostacyclin and NO
- TFPR, Heparin and Thrombomodulin inactivate Thombin.
- tPA= converts plasminogen to plasmin which destroys the clot.
Name two methods of Exchange in capillaries
Diffusion of oxygen into the cells
Bulk flow through starling forces.
List the benefits of diffusion
Self-regulating
Non-saturable
Polar molecules need to be moved via channels or pores (glucose carrier transport)
Describe Bulk Flow
Hydrostatic Pressure pushes fluid out of the capillary
Oncotic pressure pushes the fluid back in. as the protein concentration increases.
Define the quantities of fluid moved in and out.
20l out of the capillaries
17l back into the capillaries
3l drained via the lymphatic vessels.
Define Oedema
An accumulation of fluid in the Extracellular space due to a failure of lymphatic drainage or an imbalance in starling forces.
What can cause Oedema?
Blockage of Lymphatic drainage= backed up fluid
Elevated Central Venous Pressure, Low blood protein or increased capillary permeability.
