SN5
SHORT NOTE
5M
★ High-yield
Enumerate the functions of the liver.
Introduction
The liver is the largest gland in the body (1.5 kg) and performs over 500 functions. It receives a dual blood supply — portal vein (75%) and hepatic artery (25%).
Metabolic Functions
| Metabolism | Functions |
|---|---|
| Carbohydrate | Glycogenesis, glycogenolysis, gluconeogenesis — the glucose buffer of the body |
| Protein | Deamination, transamination, urea formation (the only site), synthesis of plasma proteins |
| Fat | β-oxidation, ketogenesis, synthesis of cholesterol, lipoproteins and phospholipids |
Synthetic Functions
- All plasma proteins except γ globulins — albumin (12 g/day), fibrinogen, transferrin, caeruloplasmin, haptoglobin
- Coagulation factors — all except factor VIII; including the vitamin K dependent II, VII, IX, X
- Bile salts from cholesterol
- Angiotensinogen, IGF-1, thrombopoietin
Excretory and Detoxifying Functions
- Bilirubin — conjugation by UDP-glucuronyl transferase and excretion in bile
- Detoxification of drugs — phase I (oxidation, reduction, hydrolysis by cytochrome P450) and phase II (conjugation with glucuronate, sulphate, glycine)
- Ammonia → urea via the ornithine cycle — protects the brain
- Inactivation of hormones — steroids, insulin, thyroxine, aldosterone
- Excretion of cholesterol, heavy metals and alkaline phosphatase in bile
Storage and Other Functions
- Storage — glycogen, vitamins A, D, B12 (B12 stores last 3–5 years), iron as ferritin, copper
- Haemopoiesis in the fetus (3rd–6th month)
- Destruction of RBC by Kupffer cells
- Immunological — Kupffer cells clear bacteria from portal blood
- Blood reservoir — holds 450 mL; can release it in haemorrhage
- Heat production — the greatest of any organ at rest
Applied Aspects
| Function lost | Consequence |
|---|---|
| Albumin synthesis | Hypoalbuminaemia → oedema, ascites |
| Clotting factors | Prolonged PT → bleeding tendency |
| Urea formation | ↑ Ammonia → hepatic encephalopathy, flapping tremor |
| Bilirubin conjugation | Jaundice |
| Hormone inactivation | ↑ Oestrogen → gynaecomastia, spider naevi, palmar erythema; ↑ aldosterone → oedema |
| Detoxification | Drug toxicity at normal doses |
- Prothrombin time reflects acute liver function (half-life of factor VII is 6 h); serum albumin reflects chronic function (half-life 20 days)
- The liver has an enormous reserve and a remarkable capacity to regenerate — symptoms appear only after major loss
All questions in Gastrointestinal System
- Q1Describe the composition and functions of gastric juice. Explain the mechanism of hydrochloric acid secretion and the phases of gastric secretion. ★
- Q2Describe the composition and functions of pancreatic juice. Explain the activation of its enzymes and the regulation of its secretion. ★
- Q3Describe the composition and functions of bile. Explain the enterohepatic circulation of bile salts and the functions of the gall bladder. ★
- Q4Describe the digestion and absorption of carbohydrates, proteins and fats in the gastrointestinal tract. ★
- Q5Describe the movements of the gastrointestinal tract. Explain the law of the gut and the migrating motor complex. ★
- SN1Describe the composition, functions and regulation of saliva. ★
- SN2Describe the stages and mechanism of deglutition. ★
- SN3Describe the mechanism of vomiting and the effects of persistent vomiting. ★
- SN4Enumerate the gastrointestinal hormones. Give their sources, stimuli and actions. ★
- SN5Enumerate the functions of the liver. ★
- SN6Describe the factors regulating gastric emptying.
- SN7Write a short note on peptic ulcer. ★