lecture 18 Flashcards
pepsin function as
a active proteolytic enzyme in high acid medium. HCL is as necessary as pepsin for protein digestion
pepsinogen is converted to it active form
through the contact HCl acid to form pepsin
the secretion of histamine by the ECL is
due to the direct contact of ECL with parietal cells
how is ECL stimulated
1 through the production of gastrin by the g cell
2 by the acetylcholine released from the stomach vagal nerve ending , or an hormonal substance secreted by the enteric nervous system.
gastrin is secrete by the
the gastric cells or G cells in the pyloric gland located in the distal end of the stomach
there are two form off gastrin
G 34 and G 17 , G 17 is more abundant
the main stimulus or trigger for the production of G34 and G17
is the presence of amino acid.
regulation of chief cells is by
the release of acetylcholine from the vagus nerve and stimulation of chief cell in response to acid in the stomach, affected by the intrinsic nervous system plexus
the pancreas lies
parallel to and beneath the stomach
pancreatic acini
secretes pancreatic digestive enzyme
small ductules and larger duct from the pancreatic acini secret
large volumes of sodium bicarbonate
pancreatic duct
where the combination of pancreatic enzyme and sodium bicarbonate flow through that then links with the hepatic duct before emptying into the duodenum through the ampulla vater surrounded by the sphincter of oddi
pancreas has two region
endocrine region: islet of langerhans compose of a and B cells produces insulin and glycogen
Exocrine: produces digestive enzyme called pancreatic juices
sphincter of oddi
a sphincter regulates the opening of ampulla of vater that empties into the duodenum
bicarbonate has the role of
in acidify the chyme from the stomach into the duodenum
the three most important pancreatic juices
trpsin, chymotrpisn, carboxypolypeptidase, these work in the small intestine but are produced by the pancreas
The pancreatic amylase function is
is digesting carbohydrates by hydrolyzing starch, glycogen, and other carbohydrate except cellulose
pancreatic lipase
hydrolyzes neutral fats into fatty acids and monoglycerides
all the pancreatic juices are produced in the pancreas but function in the
small intestine
Basic stimuli that cause the pancreatic secretion
acetylcholine; released by the PNS vagus nerve ending and other cholinergic nerves in the enteric nervous system .
cck: which is secreted by the duodenal and upper jejunal mucosa when foo enters the the small intestine.
secretin: secreted by the duodenal and jejunal when highly acid food enters the small intestine
acetylcholine and cck stimulate
the acinar cells causing production of pancreatic juice
secretin stimulate
secretion of large quantities of water solution of bicarbonate
Bile formation occurs in the
liver
bile contain two compounds
bile salts and bile acid, which helps to emulsify the large fat particles to be attacked by lipase, and aids in the absorption of fat end product through the intestinal mucosa membrane.
first stage of bile secretion
the hepatocyte initial secretion contains large amount of bile acids and cholesterol and substance, it is secreted into the bile canaliculi
2 stage of bile secretion
the bile flows through the canaliculi and empties into the terminal bile duct, then reaches the hepatic duct and common bile duct, from here the bile empties into the duodenum or divert through the cystic duct into the gallbladder
the function of the gallbladder is to
store to the bile produced by the liver
bile salt aids in
the digestion of fats and absorption of fats, formation of micelles , breakdown of red blood cells to form bilirubin
Jaundice
is caused by the deposit of bilirubin, free or conjugate bilirubin in the extracellular fluid, this lead to the yellowness of body tissues and skin
gallstone happen due
to the absorption of too much water
cck and the gall bladder
it induces the contraction, causing the gallbladder to empty in the duodenum that is stimulated by fatty food
Bile salt precursor is
cholesterol which can be converted to cholic acid or chenodeoxycholic acid, then conjugate with amino acid glycine and tauroine
role of bile salt
- act as a detergent or emulsifying function to decrease the surface tension, 2. helps with the absorption of fat through the formation of micelles
first stage of secretion of bicarbonate ion
CO2 diffuses to the interior of the cell from the blood and, under the influence of carbonic anhydrase , combines with water to from carbonic acid, by dissociation of result in bicarbonate and h+ion then bicarbonate is actively transported with sodium through the luminal border of the cell into the lumen of the duct
2 stage of secretion of bicarbonate ion
the hydrogen ion formed by dissociation of carbonic acid are exchanged for Na ion by secondary active transport, the Na is take to the pancreatic duct to provide electric neutrality for bicarbonate ions
3 stage of secretion of bicarbonate ion
the overall movement of sodium and bicarbonate ions from the blood into the duct lumen creates an osmotic pressure gradient that casue osmosis forming an almost completely isomotic bicarbonate solution
Brunner’s gland
is located in duodenum, it secrete alkaline mucus due to response of due to tactile or irritating stimulus on the duodenal mucosa , vagal stimulation cause increase secretion of the gland , and GI hormone( secretin)
gland of lieberkuhn
located over the entire surface of the small intestine are small pits called the crypts of lieberkuhn that lie between the villi and are cover with epithelium composed of two types of Globlets cells( mucus) and enterocytes that secretes large amount of water and electrolyte.
