Pancreas And Liver Flashcards
Decsribe the chyme in the duodenum
Low pH Hypertonic Partially digested
What are the glands in the duodenum
Duodenum - Brunner’s glands
(secrete alkaline mucosa, protecting cells lining duodenum from acidic chyme
Why is chyme in the duodenum hypertonic
-• Initial digestion of food in stomach creates solutes that make the chyme hypertonic
• Stomach wall largely impermeable to water
– Water cannot move into stomach to dilute chyme
Describe chyme as it exits teh duodenum
• Duodenum relatively permeable to water
– Hypertonic chyme draws movement of water from ECF/circulation into duodenum
• Chyme release must be controlled so as not to overwhelm duodenum!
What are the secretions from the pancreas and liver
PanceaS: enzymes, bicarbonate
Liver: bile, bicarbonate
Helps with low pH and proteins, fats and CHOs in chyme
What is released by the duodenum in response to presence of chyme
Secretin acts on pancreas to stimulate release an aqueous bicarbonate (HCO3-) component of the pancreatic secretion
CCK acts on pancreas to stimulate release of enzyme component of pancreatic secretion
CCK also acts on gallbladder (contracts) and relaxes sphincter of oddi ( see slide for location) - important it can open so secretions an be secreted in
cholecystokinin (= bile sack move)-released from duodenum in response to hypertonicity/small peptides/fats within chyme in duodenum
What is the major pancreatic function
• 90% pancreas is exocrine function
– vs much smaller proportion for endocrine function
• Pancreatic secretions (exocrine function) stimulated via gut hormones (secretin and CCK) but also autonomics
– Sympathetic inhibits
– Parasympathetic (vagus) stimulates
Decsribe the structure of the pancreas
See slide Acinar cells secrete enzymes. Duct cells secrete aqueous bicarbonate solution.mixed up in one solution once reached duct
What are the enzymes severe by the acini
• CCK (& vagus) stimulate acini (singular = acinus) to produce enzymes – Amylases and lipases (active- ready to go!) – Proteases (inactive) • Proteases (when activated) include. (Stored inactvely in zymogen granules) – Tr y ps i n – Chymotrypsin – Elastase – Carboxypeptidase
Why are Pancreatic Proteases Released in Inactive Forms?
So they do no act on pancreas itself and cause pancreatitis Protease enzymes (inactive) produced within acinar cells are concentrated and stored in zymogen granules Zymogen granules contain zymogen (in active proteases e.g. trypsinogen) which is converted to active proteases (e.g. trypsin) in intestinal lumen
What do duct cells secrete
• Duct cells secrete
– Aqueous component (isotonic)
– Bicarbonate • Will act to neutralise the acidic
chyme
What is bile
• Liver secretes bile (stored in gallbladder) into the duodenum
– Secretion of bile (250mL- 1000 mL/day)
• Bile consists of
– Bile acids and bile pigments
– Alkaline solution
• Bile plays a key role in emulsifying fat (lipids) in duodenum so that they can be readily digested by lipases secreted by pancreas
Describe the liver
Liver is largest single organ (many hugely important functions!)
• Hepatocytes are chief functional cell of liver
• Liver is highly metabolically active producing proteins and lipids for export
– Lots of rough/smooth ER
– Stacks of golgi membranes
• Contains lots of glycogen
• All blood from gut drains into liver
– Portal vein
• Bile drains from liver into gut
What are teh lobes of the liver
See slide - purely anatomical nto functionally
What are lobules
Hexagonal arrangement of cells, bile ducts and blood vessels Sheets of hepatocytes arranged towards a central hepatic venule At the 6 cornet - triad • Hexagonal arrangement • Triad of structures at each corner - Portal vein (branch) - Hepatic artery (branch) - Bile duct (branch) • Central vein in middle • Blood enters a lobule via hepatic artery and portal vein (branches of)
