Pancreas and Liver Flashcards
What is the exocrine pancreas and liver?
Accessory organ for intestines
What is the function of the exocrine pancreas and liver?
Provides excretions directly into intestine lumen to digest, lipids and proteins in the small intestine
What is the endocrine function of the pancreas and liver?
Regulate blood borne energy substrate availability by hormones. Eg. glucose, fatty acids, ketones
Properties of the pancreas?
Has both exocrine and endocrine functions
The pancreatic duct located on the 2nd part of the duodenum secretes pro-enzymes
Behind peritoneum
Close to major blood vessels making it difficult to access
Different regions of pancreas
head neck body tail uncinate
What components does the main pancreatic duct work in conjunction with?
Bile duct and the 3 components of the sphincter of Oddi
What supplies the pancreas?
The splenic artery and the pancreatico-duodenal arteries from the coeliac trunk
What are the primary functions of the exocrine pancreas?
Neutralise acid
Deliver enzymes for macronutrient digestion in duodenum
Properties of acinar cells
Main secretory cells
Clusters connected with intercalated ducts that converge on the collecting duct
What is the role of lining cells?
Add ions and secretions to acinar cells
Dependencies of pancreas regulation?
cephalic phase of digestion: vagus nerve stimulates pancreatic secretions by releasing ACh and VIP
gastric phase of digestion: regulated by vagovagal reflexes
intestinal phase of digestion: controlled by hormone secretin and CCK
What are the different enzyme secretion mechanisms in the pancreas?
zymogen granules on acinar cells
released in response to CCK
activation causing zymogen granules to exocytose from acinar cells into luminal space
What do zymogen granules do?
House inactive and active digestive enzymes
Explain how CCK regulates exocytosis of zymogen
Hormonally and neurally
CCK released into interstitial space, enters bloodstream, circulates to pancreatic acinar cells and binds to CCKA receptors
CCK can also bind to CCKA receptors on vagal afferents giving efferent stimulation of pancreatic acinar cells via VIP
Explain ion secretion in acinar cells
Basolateral CCK and ACh binding stimulates Cl- transport across apical membrane. This facilitates paracellular movement of water and Na+
Explain ion secretion in intercalated duct cells
ACh and secretin bind which activates cystic fibrosis transmembrane conductance regulators, Cl- channels and Cl-HCO3 co-transporters which recycle Cl- and HCO3
What happens with increased flow rate of ion secretion?
HCO3 increases
Cl- decreases
K+ and Na+ are unaffected
Where can the liver be palpable?
Below costal margin
What is Glisson’s capsule and where is it found?
It is a thin connective tissue layer with extensions into the organ between the lobules completely surrounding the liver
What supplies the liver?
The hepatic portal vein which brings absorbed nutrients from the gut and stomach
the hepatic artery which supplies hepatocytes with oxygen
How is bile drained from the liver?
Drained by canaliculi found between hepatocytes into bile ductules and eventually into bile ducts
Explain venous drainage of the liver?
Hepatic veins that enter the inferior vena cava
What separates the right and left lobes of the liver?
The falciform ligament
Different lobes of the liver?
Right, left and a quadrate lobe
What is the bare area of the liver?
The diaphragmatic surface with no peritoneal covering
What are the functions of the liver?
Synthesis and secretion of bile
Storage
Detoxification
Synthesis of blood clotting and anti-coagulation factors
What components are in bile?
Bile pigments, mainly bilirubin Cholesterol Phospholipids Fatty acids Water Electrolytes
What are bile pigments derived from?
Breakdown of products of haemoglobin
What are Kupffer cells and what do they do?
They are fixed phagocytes which plays a role in the formation of bile pigments
What do bile salts do?
Have a detergent and emulsifying effect of bile on fats. They also increase absorption of fats in small intestines
What does the hepatobiliary system do?
Liver produces and secretes bile by hepatocytes into canaliculi through the common bile duct into the duodenum/gallbladder until they form a common hepatic duct. Flow is in opposite direction to hepatic veins and arteries
What controls the path of bile?
Sphincter of Oddi. Contracts to deliver bile to gallbladder and relaxes to deliver to duodenum
What regulates sphincter relaxation?
CCK
What does the gallbladder do?
Stores and distributes bile
Contracts to expel bile in response to CCK
Vagal stimulation causes weak contraction
Somatostatin and noradrenaline inhibit bile acid secretion
What are the non-biliary functions of the liver?
Metabolism of CHO, protein, fat: stores and releases CHO
Detoxification: removal of ammonia, ethanol and drug transformations
Immune system: removal of intestinal bacteria from portal blood so there is none in systemic circulation
