Canonical Question
Liver – Blood Supply
Master answer
Blood flow
| Renal | Hepatic | |
|---|---|---|
| Blood Flow | 1.25l/min Highest blood flow per tissue mass | 1.5l/min Highest blood flow per organ |
| Afferent | Renal artery (from aorta) | – Hepatic artery (30%) from coeliac trunk – Portal vein (70%) from SMV, IMV and splenic veins – Hepatic artery supplies 50% of O¬2 |
| Course | Portal system → Afferent arteriole → glomerulus → efferent arteriole → peritubular capillary (inc. vasa recta) → renal vein | Via portal triad → hepatic sinusoids → central vein → hepatic vein |
| Efferent | Renal vein to IVC | Hepatic vein to IVC |
| Liver has blood reservoir function – 400ml |
Regulation
| Renal | Hepatic | |
|---|---|---|
| Hepatic arterial tone above sBP >80mmHg | ||
| Local | Myogenic mechanism – Stretch of afferent arterioles causes contraction decreasing blood flow Tubuloglomerular feedback – Na and Cl are sensed by the macula densa causing adenosine release – Adenosine constricts the afferent arteriole reducing renal blood flow | Myogenic autoregulation – Stretch of arterioles causes contraction decreasing blood flow Semi-reciprocal relationship between portal venous and hepatic arterial blood flow – Decreased blood flow via portal vein increases hepatic arterial blood flow |
| External – Hormonal | RAAS – Juxtaglomerular apparatus secretes renin in response to decreased tubular [Na] and [Cl], as well as to β stimulation – Angiotensin II constricts both afferent and efferent arterioles reducing renal blood flow | Adrenaline – Constricts portal vein and dilates hepatic artery – increasing hepatic artery contribution to blood flow Angiotensin II – Vasoconstricts both portal vein and hepatic artery decreasing hepatic artery blood flow Vasoactive intestinal peptide and secretin – Increase hepatic artery blood flow Glucagon – Increased hepatic blood flow |
| External -Neural | – Sympathetic stimulation constricts the renal afferent and efferent arterioles reducing renal blood flow | – Sympathetic (α adrenergic) stimulation by noradrenaline causes portal venous constriction and decreased hepatic blood flow |
| External -Starling resistors | – Increased intra-abdominal pressure will decrease blood flow in starling resistor model – Increased intra-capsular pressure will decrease renal blood flow | Respiration – Inspiration decreases hepatic venous blood flow |
| External – dietary | High blood amino acid/ glucose level – vasodilation and increased renal blood flow | Post-prandial – Increased splanchnic blood flow – increased portal venous blood flow |
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2012A Q11 | Compare and contrast renal and hepatic blood flow and its regulation | historical_member | 70.00% |
| 2015B Q03 | Compare and contrast renal and hepatic blood flow, and their regulation | historical_member | 54.00% |