Week 6 Pancreas and Liver Flashcards
why is chyme hypertonic?
food produces lots of solutes that are dissolved in gastric juice
stomach wall is largely impermeable to water so water cannot dilute solute in chyme= >tonicity
what are the key properties of chyme?
hypertonic chyme enters duodenum from stomach
its acidic and only partially digested
how is chyme neutralised?
duodenum is relatively permeable to water- when hypertonic chyme moves in water enters from ECF/circulation into duodenum
chyme release must be controlled- too much can overwhelm duodenum
- chyme is isotonic when it leaves the duodenum
secretions from:
pancreas- enzymes, bicarbonate ions
liver- bicarbonate ions, bile
describe secreted by the exocrine pancreas acinus?
acinus- stimulated by vagus and cholecystokinin (CCK)
- hypertonicity/ fats detected in duodenum
- produces enzymes
- amylases/lipase (active)
- proteases- trypsin, chymotrypsin, elastase, carboxypeptidase (inactive)
describe secretions by the exocrine pancreas duct cells?
- aqueous component
- isotonic solution- Na, Cl, K, HCO3
- secretes HCO3- stimulated by secretin (neutralise acid chyme)
- inside cell
- CO2 + H2O -> H2CO3
- H2CO3 -> H+ + HCO3
- HCO3 moved into lumen (Cl HCO3 exchanger)
- inside cell
what are zymogen granules?
membrane bound- contain zymogen- inactive pre-cursar of an enzyme- avoids digesting pancreas
- eg trypsinogen-> trypsin (in intestinal lumen)
if pancreatic enzymes (amylase) appear in blood- signifies pancreatic damage
what does the liver do and how is this related to GI?
largest organ
- energy metabolism, detoxification, plasma protein production
- in gut- secretes bile (250ml-1L/day)
- bile acids and alkaline juice, excretion of bile pigments
what are hepatocytes and what do they do?
chief functional cell of the liver, comprise approx 80% of the lass of the liver
very active at producing proteins/lipids for export
- contains lots of rough/smooth ER, and stacks of golgi
contains lots of glycogen
within a functional unit of a liver acinus what is within a triad?
contains portal vein, hepatic artery and bile duct - feeding into central canal
where and by what does all the blood from the gut drain into?
via portal vein to liver
how are the enzymes produced and released from the pancreas?
formed by RER- moved to golgi (cis then to trans)- condensing vacuoles- concentrated in zymogen granules- released with appropriate stimulus
what proportion of the pancreas is exocrine in function, what is the basic structure and how is it innervated?
exocrine portion 90% of pancreas, 2% endocrine
- basic structure- acinus- enzymes, ducts- modifies aqueous secretions
- innervated by:
- sympathetic- inhibits
- parasympathetic- vagus- stimulated
what is flowing in and out of the liver?
blood flowing in - venous portal blood, arterial blood (hepatic arteries- flowing towards central vein- hepatic venins (vena cava)
bile flowing out- along canaliculi- bile ducts to duodenum
what are the components of bile?
bile acid dependant- secreted into canaliculi by hepatocytes- contains bile acids and pigment
bile acid independent- secreted by duct cells- similar to alkaline solution to panctreatic duct cells- stimulated by secretin
how does the microscopic structure of the liver relate to its function?
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