GI Physiology - Liver and Pancreas

Question 1

Describe the anatomy & blood supply of the liver

Answer 1

Largest endocrine organ, weighing approx 1.5kg

Contained within fibrous capsule, divided into 4 main lobes
Left, right (biggest), quadrate and caudate.
Each lobe formed of microscopic hexagonal lobules, containing hepatocytes, sinusoids and bila canaliculi.

Five ligaments connect it to surrounding abdominal walls and diaphragm superiorly
Round, coronary, right & left triangular, and falciform ligaments

Blood supply from hepatic portal vein & hepatic artery, supplying corners of each lobule, with the hepatic vein draining from the centre of the lobule

Takes 30% of cardiac output (~1800ml/min) - 70% from portal vein, 30% from hepatic artery.

Question 2

Describe the roles of the liver

Answer 2

Synthetic
Bile acids produced from cholesterol
Protein synthesis, particularly albumin
Globulins & clotting factors

Metabolic & excretion
Drug metabolism
Bilirubin conjugation & excretion
Enterohepatic circulation of drugs
Protein catabolism & urea production via ornithine cycle
Glycogenesis, gycogenolysis and gluconeogenesis
Fatty acid synthesis
Metabolism & breakdown of hormones (ADH, aldosterone, steroids, thyroxine)

Storage
Vitamins A, D, K, B12, Folate
Glycogen

Immune
Kupffer cells are resident macrophages

Haematological
Haematopoeisis in the foetus
Reservoir of blood
Clearance of old erythrocytes

Question 3

What is the role of the pancreas?

Answer 3

80% Exocrine enzyme production
Lipase
Amylase
Trypsin
Chymotrypsin
Other digestive enzymes
Bicarbonate

20% Endocrine function
Insulin
Glucagon
Somatostatin