Compare and contrast renal and hepatic blood flow, and their regulation.
It was expected candidates would describe the salient features of the anatomy, distribution and
content of blood flow and influences on each circulation. Answers with a clear organisation and
context for the normal influences of blood flow on the functioning of each organ system scored
highly. Anatomy was often sufficiently covered, but candidates often did not take advantage of
that by linking the anatomical features to the functional concepts. Figures should be clearly and accurately labelled to score well. Many answers failed to demonstrate a depth of understanding
of key concepts. For example tubuloglomerular feedback, relationship between hepatic arterial
and portal venous flows and autoregulation within both those systems was often poorly
described.
This question is identical to Question 11 from the first paper of 2012, except with better grammar.
| Domain | Hepatic circulation | Renal circulation |
| Anatomy of blood supply | Portal vein (70%) Hepatic artery (30%) |
Renal arteries (100%) |
| Blood flow (ml/min) | total = 1500 ml/min | total = 1100 ml/min |
| Blood flow (% of CO) |
25% of cardiac output | 20% of cardiac output |
| Venous drainage | Hepatic veins | Renal veins |
| Oxygen consumption | 6ml O2/100g/min | 2ml O2/100g/min |
| Blood flow distribution | Arterial and portal venous blood mix in hepatic sinusoids | 95% of flow goes to the renal cortex, 5% to medulla |
| Capillary beds | Hepatic sinusoids (large diameter low-pressure capillaries with discontinuous endothelium) | Glomerular capillary bed; peritubular capillary bed |
| Function | Metabolic activity Blood storage reservoir |
Filtration Clearance of waste substances |
| Regulatory mechanisms | Portal venous flow regulation:
Hepatic arterial flow regulation:
|
Local arterial autoregulation:
Systemic autoregulation:
Extrarenal factors affecting flow:
|
Eipel, Christian, Kerstin Abshagen, and Brigitte Vollmar. "Regulation of hepatic blood flow: the hepatic arterial buffer response revisited." World journal of gastroenterology: WJG 16.48 (2010): 6046.
Abshagen, K., et al. "Anatomy and physiology of the hepatic circulation." PanVascular Medicine (2015): 3607-3629.
Greenway, C. V., and R. D. Stark. "Hepatic vascular bed." Physiological reviews 51.1 (1971): 23-65.
Dancygier, Henryk. "Hepatic Circulation." Clinical Hepatology. Springer, Berlin, Heidelberg, 2010. 55-
Wilkinson, Grant R., and David G. Shand. "A physiological approach to hepatic drug clearance." Clinical Pharmacology & Therapeutics 18.4 (1975): 377-390.