lecture 18 - splanchnic & hepatic circulation

Question 1

What is the purpose of auto-regulation of blood flow in the GI tract?

Answer 1

Maintains blood flow to the gut, particularly in a fed state, despite fluctuations in blood pressure due to exercise, illness, posture, etc.

Question 2

Why does the SNS sometimes override the auto-regulation of GI tract blood flow?

Answer 2

SNS will sometimes cause vasoconstriction to divert blood from the GI tract to maintain perfusion of other more vital organs when the MABP drops dramatically

Question 3

Why are villi vulnerable to hypoperfusion if blood flow to the gut is reduced?

Answer 3

The tips of the villi are prone to ischaemia when circulatory shock occurs, because they only receive 20% of blood flow due to the countercurrent bloodflow, which is insufficient in flow drops.

Question 4

What is the key risk of severe hypoperfusion of the gut during shock?

Answer 4

Villi are underperfused and become ischaemic, interrupting the mucosal barrier and allowing bacteria to enter the circulation causing sepsis.

Question 5

What is the effect on the liver during cardiac failure?

Answer 5

Right atrial pressure rises causing back flow of blood to the liver, which expands to hold more blood.

Question 6

How does cirrhosis cause portal hypertension?

Answer 6

Cirrhosis causes decreased blood flow in the portal system due to increased portal vascular resistance. this results in a back up of pressure in the portal vein