Exchange and the Lymphatic System Flashcards
Capillaries are specialised for
exchange
What cell type are capillaries composed of?
Endothelial
What feature of capillaries presents a small diffusion barrier?
Thin walls (one cell)
Other than thin walls, what feature of capillaries allows fast diffusion?
Large surface area
Give a distinguishing factor of fenestrated capillaries
Presence of large pores
What is the function of endothelial cell junctions?
To control which molecules leave the capillary
What type of capillary allows larger structures such as proteins and cells to leave?
Discontinuous
Capillaries are composed of one endothelial layer and
it’s concordant basement membrane
In what type of capillary are there no clefts or channels?
Continuous
In what type of capillary are there clefts and channels? (not massive channels)
Fenestrated
Fibrin monomers are cleaved from
fibrinogen
Fibrin monomers are cleaved by
thrombin
When the lining of a blood vessel breaks and endothelial cells are damaged, what fibres are exposed?
Collagen fibres
What component of the blood adheres to damaged endothelium?
Platelets
What is formed in the adherence of platelets to damaged endothelium?
Platelet plug
What is haemostasis?
The process of keeping blood inside a damaged blood vessel to stop bleeding
What happens to platelets when they stick together and to the proteins in the vessel wall which stimulates further platelet activation?
Platelets degranulate
If platelets alone are not enough to stop the bleeding from a vessel, what protein is released to strengthen the platelet plug?
Fibrin
What two substances act as chemical messengers and inhibit platelet aggregation and formation of the platelet plug?
Prostacyclin and nitrous oxide
What substance stops thrombin production?
Tissue factor pathway inhibitor (TFPI)
What substance binds and inactivates thrombin?
Thrombomodulin
What substances are expressed by TFPI to inactivate thrombin?
Thrombomodulin and Heparin
What is the function of plasmin?
To degrade blood clots
Why do cells have a lower concentration of oxygen than capillaries?
As cells are constantly respiring and using oxygen
What is the order of the concentration gradient for oxygen, from highest to lowest, between cells, capillaries and ECF?
Capillary, ECF, cells
What effect will increased usage of oxygen by cells have on the concentration gradient, meaning diffusion is non-saturable?
Concentration gradient will increase as will the volume of oxygen diffusing
Do polar or non-polar substances cross the cell membrane in diffusion?
Non-polar
What substances pass through clefts/channels in cell membranes?
Polar substances
What is the carrier mediated transport system used in the brain?
Glucose transporter
What is the trend in hydrostatic pressure from arteriole to venule through capillaries?
Hydrostatic pressure decreases
What is the trend is osmotic pressure from arteriole to venule through capillaries?
Osmotic pressure increases
Approximately how many litres of water is pushed into the lymph capillaries every day?
3 litres
What pressure draws more water into the capillaries?
Osmotic pressure
What causes the fluid in lymph vessels to be pushed back towards the CVS?
Lymph vessels pass through contracting muscle which squeeze the lymph vessel and push fluid towards the CVS
What is an oedema?
Accumulation of excess fluid
What effect does oedema have on central/mean venous pressure?
Causes a rise in CVP
Other than raised CVP, give an effect of oedema
- lymphatic obstruction
- hypoproteinemia
- increased capillary permeability
