State the 3 key properties of chyme leaving the stomach
3) Partially Digested
What are the bile acid dependent components of bile? Where are they secreted from?
o Secreted into canaliculi by hepatocytes
o Contains bile acids and pigments: Acids include – cholic acid, chenodeoxycholic acid conjugated to AAs
What are the bile independent components of bile? What secretes it?
o Secreted by duct cells
o Contains alkaline juice like pancreatic duct cells
What is the structural unit of the liver?
Describe the structure of a structural unit of the liver.
Central vein in the middle.
Each corner has a portal triad which contains:
1) Arteriole - branch of hepatic artery, entering liver
2) Venule - branch of hepatic portal vein, entering liver
3) Duct - leaving liver
State the dual blood supply of the liver.
• Arterial blood from the coeliac trunk – the hepatic artery proper
• Hepatic portal vein, from which nutrients and toxins taken from the small intestine are drawn to the liver.
What are the secretions of the exocrine pancreas?
• Alkaline juice – water, few ions, lots of bicarbonate
o Proteases – Trypsinogen, chymotrypsinogen, proelastase, pro-carboxypeptidase
What is the exocrine gland of the pancreas made up of? What does each part secrete? Explain how pancreatic enzymes are synthesised and secreted.
Exocrine gland is made up of acini and ducts. Acini secrete enzymes and ducts secrete alkaline juice.
1. Enzymes synthesised on ribosomes as inactive precursors and packaged into condensing Vacuoles by golgi complex
2. Forms zymogen granules ready to be secreted
3. When signal received, zymogen granules secreted by exocytosis and activated in intestine by enzymatic cleavage
State a biomarker for pancreatic disease
What hormone stimulates pancreatic acinar secretions?
acinar secretion stimulating hormone - Where is it released from and what is it stimulated by? What other functions does it have? How does this hormone allow the pancreas to begin making enzymes when food is placed into the mouth?
• CCK released from duodenal APUD cells
• Stimulated by hypertonicity and fats in duodenum.
• Receptors for CCK and gastrin are very similar and therefore can be stimulated by each other. CCK inhibits secretion of acid into the stomach
• Vagus nerve also stimulates CCK by the release of Ach – Acini are innervated by branches of vagus nerve, allows pancreas to begin to make enzymes when you first put food in your mouth.
Explain the process by which alkaline juice is made
Alkaline juice produced by duct cells:
1) HCO3 present in blood at elevated concentration due to gastric secretion of acid
2) Sodium conc gradient generated by Na-K-ATPase, with high sodium in ECF and low in cell
3) Na-H+ antiporter used to get Na into cell and H+ out of cell.
4) H+ combines with HCO3 in ECF to form h2o and co2.
5) CO2 taken into cell and combines with H2O to form H+ and HCO3
6) HCO3 enters lumen.
What hormone stimulates duct secretion? Where is it released from and in response to what? What relationship does this hormone have to the acinar secreting hormone?
Duct secretion is stimulated by secretin which is released by jejunal cells in response to low pH.
CCK allows secretin to bind more effectively to receptors.
Explain how bile acids digest fats
1) Emulsify fat into much smaller globules = Increase SA for lipases to act
2) Lipases digest the globules and release FFAs. Released fatty acids form micelles with bile acids which contain cholesterol, vitamins and phospholipids
3) Micelles carry FAs and other things to unstirred layer next to epithelial cells
4) Fatty acids etc are released slowly, entering the cells by diffusion.
5) Fatty acids are then resynthesized to lipids in epithelial cells and exported to lymphatics as chylomicrons.
Where is bile acid stored and how is it stored?
Stored in gall bladder and concentrated by reduction of volume (transport of salt and water across gall bladder epithelium)
How is bile released from its storage area?
• CCK secreted by duodenum stimulates contraction of gall bladder muscle
• Ejects concentrated bile acids
What happens to bile acids after usage?
Once used, Bile acids then continue to terminal ileum where they are actively absorbed by epithelia and return to the liver via hepatic portal blood. Hepatocytes actively take up the bile acids and re-secrete them into the canaliculi.
Some bile acids lost – unconjugated by bacterial action in gut. Hepatocytes synthesise new ones to replace.
What is the condition called where fat appears in faeces? Why would it occur?
Steatorrhea - not enough bile acids or pancreatic enzymes secreted
What is the fibrous layer that covers the liver called?
What are the 3 sections that make up the gallbladder? Which section is a gallstone most likely to be lodged?
o Fundus – Rounded end portion of gallbladder. Projects into inferior surface of liver
o Body – Mid section. In contact with transverse colon and proximal duodenum.
o Neck – Connects to the cystic duct. Common location for gallstones to become lodged
What is the relationship between the IVC and the liver?
Liver attached to IVC right through the middle
Hepatopancreatic ampulla of Varter
Label the tributaries of the hepatic portal vein
Name the arteries which supplies the pancreas.
• Supplied by splenic artery
• Head is also supplied by the superior and inferior pancreaticduodenal arteries which are branches of the gastroduodenal and superior mesenteric arteries
Name the venous drainage of the pancreas
Venous drainage of the head is by superior mesenteric vein and by the splenic veins
Name the arterial and venous drainage of the spleen
Splenic artery and vein
How does H. pylori modify gastric physiology and result in peptic ulcers?
• Bacteria colonising the pyloric antrum results in inflammation which induces G cells to secrete Gastrin
• Gastrin stimulates parietal cells to produce more acid into stomach lumen, increasing acid load damaging the duodenum and forming ulcers.