This module is deliberately lopsided, and the shape is not an editorial preference. Two of its six lessons are the liver, two are the upper gut, one is the intestine and one is the organisation that the other five assume. Everything the module teaches is taught to the depth the physiology needs; what the weighting decides is how much room each part gets, and the room follows what the subject actually turns on. The liver is the organ the rest of the abdomen drains through, and the lower oesophageal sphincter is the reason a fasted patient is not necessarily a safe one.
Orientation
What this module covers, and how to work through it
Alimentary and hepatobiliary physiology is one syllabus line covering two organs that behave nothing alike. The gut is a tube with a nervous system of its own, running a set of mechanical and secretory programmes that anaesthesia interrupts at almost every step. The liver is a chemical plant with a circulation unlike any other organ’s: a quarter of the cardiac output arriving down two pipes at different pressures and different saturations, one of which can compensate for the other and one of which cannot.
The module is built to be used two ways. Read straight through, it follows a meal: how it is swallowed, what the stomach does to it, how the intestine takes it apart, and what the liver does with what arrives. Used as reference, any single lesson stands alone — it opens with what it assumes, links to those lessons, and states its own learning outcomes so you can tell when you are done with it.
Prerequisites for the module as a whole
These carry material this module builds on directly and does not repeat. Work through them first if they are not already secure:
- Cellular physiology — membranes and transport: secondary active transport, facilitated diffusion and osmosis, which every absorptive and secretory mechanism in this module applies rather than re-derives.
- Cardiovascular — the circulation: the pressure-flow-resistance relationship, capacitance and venous return, which the splanchnic and hepatic circulations specialise.
- Pharmacokinetics — clearance and the extraction ratio: the clearance equation and the high- against low-extraction distinction. Lesson 5 uses them as circulatory physiology and does not re-derive the kinetics.
Syllabus
MMed syllabus mapping
| Syllabus area | Lessons | What is covered |
|---|---|---|
| Organisation and control of the gut | Lesson 1 | The layers of the wall; the enteric nervous system and its two plexuses; the extrinsic autonomic supply; the gastrointestinal hormones and their two families; paracrine and immune signalling; the splanchnic circulation and its capacitance role |
| The upper gastrointestinal tract | Lessons 2-3 | Deglutition and airway protection; the two oesophageal sphincters; barrier pressure and the physiological factors preventing reflux; the parturient; the parietal cell and acid secretion; the three phases of secretion; mucosal protection; gastric motility, emptying, volume and pH |
| The intestine | Lesson 4 | Segmental and propulsive motility and the migrating motor complex; pancreatic exocrine secretion; digestion and absorption of carbohydrate, protein and fat; water, electrolyte and vitamin handling; the colon, continence and defaecation; ileus and obstruction |
| The liver | Lessons 5-6 | Lobule, acinus and zonation; the sinusoid and the space of Disse; the dual blood supply and the hepatic arterial buffer response; intrinsic and extrinsic control; ventilation, anaesthesia and surgery; clearance and extraction ratio; the metabolic, synthetic, storage, protective and excretory functions; bile and bilirubin; the role in acid-base balance; assessment; acute liver failure |
Four adjacent topics deliberately sit elsewhere. The vomiting reflex is taught in the antiemetics module, where the vomiting centre, the chemoreceptor trigger zone and the five afferent routes each get a section; lesson 3 teaches the gastric side of the problem and links out rather than re-teaching the reflex. Hepatic drug metabolism belongs to pharmacokinetics, which already carries cytochrome P450, the phase I and II reactions and the extraction-ratio arithmetic; lessons 5 and 6 give extraction ratio as circulatory physiology and phase I and II as hepatic function, and link out for the kinetics. The endocrine pancreas belongs with metabolic and endocrine physiology; the exocrine pancreas is taught here, in lesson 4, because pancreatic juice is a digestive secretion. Aspiration prophylaxis drugs are a pharmacology objective; lessons 2 and 3 teach the physiology those drugs act on and stop there. The splanchnic circulation is the one that moves the other way: it is named by the cardiovascular regional-circulations objective, and it is taught here, in lesson 1, because it is the gut’s own circulation and the capacitance argument only makes sense beside the gut.
The pathway
All 6 lessons, in order
Part I
The gut as an organ
One plan of wall, one nervous system, one set of hormones and one circulation, repeated from oesophagus to anus. Nothing later in the module works without these.
- The gut as an organ, and how it is controlled
One plan of wall repeated from oesophagus to anus, a nervous system of its own that outnumbers the spinal cord, an extrinsic supply that only modulates it, and a circulation that doubles as the body's largest reservoir of blood.
Part II
From mouth to colon
A meal, followed through: how it is swallowed without entering the airway, what the stomach does to it and how fast it lets it go, and how the intestine takes it apart and takes it up.
- Swallowing, the lower oesophageal sphincter and barrier pressure
The most examined non-liver topic in the section, asked four times in four different ways: how a bolus gets past an airway without entering it, what holds the stomach shut, and what the subtraction that defines competence actually is.
- The stomach
One cell that moves a proton against a millionfold gradient, three phases that decide how much of it there is, a mucus layer that stops it digesting its own wall, and the volume and pH that decide how much an aspiration would cost.
- The small and large intestine
Two hundred and fifty square metres of absorptive surface, nine litres of fluid presented to it each day, and two hundred millilitres that leave in the stool: the arithmetic of how a meal becomes portal blood.
Part III
The liver
The organ everything absorbed from the gut passes through before it reaches anywhere else. Its circulation first, because zonation, drug handling and the pattern of injury are all consequences of it, and then what it does.
- The liver: structure, blood supply and hepatic blood flow
A quarter of the cardiac output arriving down two pipes at different pressures and different saturations, one of which can compensate for the other and one of which cannot. Asked in 2019, in October 2024 and again in April 2026.
- The liver: function, and the failing liver
The question the record asks most often, and the one candidates most often answer as an unordered list. Six headings, what each one costs when it stops, and the tests that do and do not measure it.
Objectives
The full objective wording
- Organisation and controlOrganisation of the gut wall, the enteric and extrinsic nervous supply, the gastrointestinal hormones and the splanchnic circulation
- Swallowing and the LOSSwallowing, the oesophageal sphincters, barrier pressure and the physiological factors preventing reflux
- The stomachGastric secretion and its control, mucosal protection, gastric motility and emptying
- Intestine and absorptionIntestinal motility, pancreatic exocrine secretion, digestion and absorption, and colonic function
- Hepatic circulationHepatic structure and zonation, the dual blood supply, the control of hepatic blood flow, and hepatic clearance
- Liver function and failureThe metabolic, synthetic, storage, protective and excretory functions of the liver, their assessment, and acute liver failure