Pancreas and Liver Flashcards
What are the functions of the exocrine liver and pancreas?
Provide excretions directly into digestive lumen to:
- digest carbs, proteins, lipids in the small intestine BEFORE ABSORPTION HAS TAKEN PLACE.
- neutralize acid remaining from stomach (using HCO3-)
What is the function of the endocrine liver and pancreas ?
Regular blood borne energy substrate availability via hormones AFTER ABSORPTION HAS TAKEN PLACE.
What are examples excretions the exocrine pancreas secretes ?
Pro-enzymes, HCO3- (helps neutralise acid)
How are the digestive secretions secreted into the small intestine ?
Via pancreatic duct to the 2nd part of the duodenum.
Where is the pancreas located ?
Retroperitoneal (part of abdomen behind peritoneal cavity), close to major blood vessels. Lies in C shaped curve of duodenum (except tail)
What are the different parts of the pancreas ?
Tail, Body, Head, Neck, Uncinate Process
What other structures does the pancreatic duct connect with ?
With the common bile duct, and the 3 components of the sphincter of Oddi
How is the pancreas supplied with blood ?
Mainly by
- the splenic artery (from coeliac trunk)
- the pancreatico-duodenal artery (from coeliac trunk or Superior Mesenteric Artery)
What are the main secretory cells of the exocrine pancreas ?
Acinar cells
What substances do these cells secrete ?
Enzymes, Na+, K+, Cl-, HCO3-, serous secretions
How are acinar cell clusters connected?
By intercalated ducts
Where do these intercalated ducts converge?
In collecting duct
Which substances do the ductal cells (the cells lining the duct) add to the secretion ?
Serous and HCO3- secretions
During which phase of digestion are most of the secretions of the exocrine pancreas produced ? How are the secretions controlled in that case ?
Intestinal phase (about 65%). Secretions are controlled hormonally by secretin (in response to acid) and CCK (in response to AAs, FAs, monoacylglycerols).
How are the secretions of the exocrine pancreas regulated during the cephalic phase ? And how much pancreatic secretions are produced?
About 25%
Vagus nerve is stimulates pancreatic secretions by releasing ACh and VIP
How are the secretions of the exocrine pancreas regulated during the gastric phase ? And how much pancreatic secretions are produced?
About 10%
Mediated by vagovegal reflex
What are zymogen granules ?
- Found in acinar cells
- House mainly inactive digestive enzymes
- Secreted by exocytosis from Acinar cells into luminal space upon activation
- Secretion occurs in response to CCK, VIP and Gastric-releasing peptide
How is exocytosis of zymogen granules (for release of enzymes) exactly regulated ?
Regulated hormonally and neurally.
-CCK is released into interstitial space —> enters bloodstream —-> travels to pancreatic acinar cells —–> binds to CCKA receptors —–> stimulation of acinar cells
-CCK is released into interstitial space —> enters bloodstream —-> travels to vagal afferent —–> binds to CCKA receptors —–> gives efferent stimulation of acinar cells via VIP
How is ion secretion by Acinar cells regulated ?
Basolateral CCK and ACh binding in acinar cells —> Stimulates Cl- transport across apical membrane —> Paracellular Na+ and water movement facilitated
How is ion secretion by intercalated ductal cells regulated ?
Secretin and ACh binding in ductal cells —-> Cystic fibrosis transmembrane conductance regulators, Cl- channels, Cl-HCO3- co-transporters activated
How does the pancreatic secretion flow rate affect ionic concentration of HCO3-, Cl-, Na+ and K+ ?
With increased flow rate:
Increased HCO3-
Decreased Cl-
Unaffected Na+ (similar to plasma Na+) and K+ (slightly higher than plasma K+)
Where is the liver relative to surrounding structures ?
Across the upper abdomen, under the diaphragm, surrounded by peritoneum. May be palpable below costal margin.
What is Glisson’s capsule ?
Thin connective tissue layer sending extensions into the liver, in between the lobules. Surrounds the liver deep to its peritoneal covering
What major blood vessels are in the liver ?
Hepatic portal vein brining absorbed nutrients from stomach and gut. Hepatic artery supplying the hepatocytes with oxygen.
What are hepatocytes ?
Liver cells
How is bile drained ?
Via canaliculi which lie between the hepatocytes into bile ductules and eventually into bile ducts.
How is veinous drainage in the liver ?
By hepatic veins which enter the inferior vena cava.
How many lobes does the liver have ? What are they called ?
4
Right, left, caudate and quadrate
Where is the quadrate lobe located ?
Next to the gallbladder
Where is the caudate lobe located ?
Next to the IVC
How are the R and L lobes seperated ?
Via falciform ligament
What is the bare area (uncovered by peritoneal covering) called ?
Diaphragmatic surface
What are the functions of the liver ?
- Synthesis and storage of bile
- Storage of glucose, glycogen, proteins, vitamins, and fat
- Detoxification of metabolic waste
- Synthesis of blood clotting and anticoagulant factors (fibrinogen and prothrombin)
What is bile made of ?
Bile acids, Bile pigments (mainly bilirubin), cholesterol, phospholipids (lecithin), water and electrolytes.
Where are bile pigments derived from?
Breakdown products of haemoglobin. Kupffer cells play a role in their formation.
What is the role of bile salts/bile acids ?
- Responsible for detergent and emulsifying effect of bile on fats
- Increase absorption of fat by small intestine
How does the sphincter of Oddi control the flow of bile ?
- Closed (contracted), mainly to gallbladder
- Open (relaxed), mainly to duodenum
How can sphincter relaxation by achieved ?
Hormonally, through CCK
What is bile from the liver called ?
Hepatic bile
Describe the path of the bile from the hepatocyte to common hepatic duct.
Hepatocyte —-> canaliculi —> bile ducts —-> common hepatic duct
What is the orientation of bile flow relative to hepatic artery and portal vein ?
Bile flow is in opposite direction of blood from hepatic artery and portal vein (bile drains to the outside whilst hepatic and portal blood drain central)
How is bile concentrated ?
Na+ and Cl- are reabsorbed causing isotonic water reabsorption (hence bile concentrated). As a result gallbladder bile is more concentrated than liver bile.
How do liver bile and gallbladder bile compared in terms of molecular content ?
Gallbladder bile has more of everything except Na+ and Cl-
What is the function of the gallbladder ?
Storing and distributing bile in concentrated form
How does the gallbladder get stimulated/inhibited to distribute the stored bile ?
-Fats and proteins are sensed in the duodenum which causes I cells to release CCK which stimulates gall bladder contraction + vegal stimulation also causes contraction (mainly CCK)
Both of these also result in the sphincter of Oddi to relax and hence open to allow hepatic bile to drain into the duodenum
-Samastotin and noradrenaline inhibit bile acid secretion
What are examples of biliary functions of the liver ?
- Metabolism- of carbs, proteins, fat, certain minerals, and lipid soluble vitamins. Store vs release depending on Fed vs Fasted state (For instance stores and releases carbohydrate: glycogenesis “when high glucose levels in blood” when and glycogenolysis to “release glucose into bloodstream”)
- Detoxification- (for instance drug biotransformation, and removal of ammonia and ethanol and hormones)
- Immune system function- removal of intestinal bacteria from portal blood with Kupffer cells (engulf bacteria which may have crosses intestinal lumen into circulation). Hence produce large amounts of lymph
