Exchange and the lymphatic system Flashcards
what are the 3 different structures of capillaries?
continuous
fenestrated
discontinuous
describe continuous capillaries.
may have no clefts or channels
may have no channels but clefts only
where is a continuous capillary with no channels or clefts found?
brain
where is a continuous capillary with clefts found?
muscle
describe fenestrated capillaries.
contain clefts and channels
where can a fenestrated capillary be found?
intestine
describe a discontinuous capillary.
clefts and massive channels
where can a discontinuous capillary be found?
liver
what is the action of thrombin?
thrombin converts fibrinogen into fibrin
fibrin is involved in clot formation
does prostacyclin increase or inhibit platelet aggregation?
prostacyclin inhibits platelet aggregation
does NO inhibit or increase platelet aggregation?
inhibits platelet aggregations
what are the different anti-clotting mechanisms of the endothelium?
stops blood contacting collagen
produces prostacyclin and NO
Produced tissue factor pathway inhibitor (TFPI)
expresses thrombomodulin
expresses heparin
secretes tissue plasminogen activator (t-PA)
what is the role of tissue plasminogen activator?
activates plasminogen.
activated plasminogen is converted to plasmin which lyses and breaks down clots
what is the role of tissue factor pathway inhibitor?
stops thrombin production
what are the benefits of diffusion?
self regulation
non-saturable
non-polar substances can cross membrane
polar substances can travel through clefts and channels
as you go along from arteries to venules, does the hydrostatic pressure increase or decrease?
decreases because pressure is higher in arteries thus higher hydrostatic pressure
does the oncotic pressure increase or decrease as you move from arteriole to venules?
and why?
increases
as the water is lost due to increasing hydrostatic pressure, the proteins remain in the capillaries therefore increasing the concentration.
the increase in concentration builds up the oncotic pressure which draws more water into the capillaries.
what is the volume of fluid lost and gained each day through the capillaries?
20l lost
17l regained
remaining 3l drained by lymphatic system
what can increase capillary permeability?
inflammation e.g rheumatism
