Exchange and the Lymphatic System

Question 1

Name some factors of the gross structure of the venous system and allow for exchange.

Answer 1

• lots of precapillary sphincters
• thin walls present a small diffusion barrier
• small diameter, therefore a big surface to volume ratio

Question 2

What word would you use to describe the cell junctions of continuous capillaries?

Answer 2

• leaky

Question 3

What two things in to be formed correctly in order to successfully clot blood?

Answer 3

• formation of a platelet plug

- formation of a fibrin clot

Question 4

Describe the six anti-clotting mechanisms of the endothelium.

Answer 4

• stops blood contacting collagen - not platelet aggregation
• produces prostacyclin and NO - both inhibit platelet aggression
• produced tissue factor pathway inhibitor (TFPI) - stops thrombin production
• expresses thrombomodulin - binds thrombin and inactivates it
• expresses heparin - also inactivates thrombin
• secretes tissue plasminogen activator (t-PA) - plasminogen is reduced to plasmin and digests clot

Question 5

Define oedema.

Answer 5

• accumulation of excess fluid