functions of GI
digestion
absorption
excretion
endocrine
what are the two secretions in the mouth
salivary amylase - breaks down carbs and starches
lingual lipase - breaks down fat
what are the 3 gastric glands
mucosal or neck cells - secrete mucus and gastrin
chief cells - produce pepsinogen
parietal cells - produce HCL and intrinsic factor
what cells secrete gastrin
what does it do
mucosal/neck cells - G cells
stimulate HCL gastric secretions
what cells secrete pepsinogen
what does it do
chief cells
HCL converts pepsinogen to activated pepsin which breaks down proteins and collagen
what cells secrete HCL and intrinsic factor
what does it do
parietal cells
HCL - destroy bacteria and activate pepsinogen
intrinsic factor - absorbs B12 in terminal ileum
mixture of food and gastric secretions is called
chyme
chyme is propelled through SI by
peristaltic waves
presence of chyme in the SI stimulates release of what
secretin
what cells and where is secretin secreted
what does it do
S cells found in duodenum
stimulates pancreatic acinar cells to secrete bicarbonate and water
also decreases gastric motility
what glands secrete bicarbonate
where
what does it do
brunners glands in duodenum
neutralizes the gastric acid
makes PH more alkaline in SI
what protects the duodenal wall from digestion from highly acidic gastric juices
bicarbonate
the presence of fat in the duodenum stimulates the release of what
CCK
what cells release CCK
where
what does it do
I cells in the duodenum
causes gall bladder to contract
causes sphincter of oddi to relax - allows bile excretion into the duodenum
stimulates pancreas to secrete enzymes
what pancreatic enzyme completes the break down of of starches into maltose
what is it secreted by
pancreatic amylase
exocrine cells / acinar cells
what does maltase do
breaks down maltose to 2 molecules of glucose
what does lactase do
breaks down lactose to glucose and galactose
what does sucrase do
breaks down sucrose into glucose and fructose
where are maltase, surcase, and lactase found
brush border of enterocytes
starches break down into what
maltose
some digested fat is absorbed into the lacteals and drain into what
thoracic duct
what enzymes digest polypeptides to produce amino acids
intestinal peptidases
what are the final products of breaking down fat, starch, and protein in the SI
fats - fatty acids and glycerol
starch, sucrose, lactose - glucose, fructose, galactose
proteins - amino acids
breakdown products (fat, starches, proteins) are __ by the small intestine and transported to the __ except what
absorbed
liver
except some fat travels in lacteals to thoracic duct
is the pancreas an endocrine, exocrine, or both gland
both
what are the endocrine cells of the pancreas
what are the exocrine cells of the pancreas
endocrine - islets of langerhans
glucagon - alpha cells
insulin - beta cells
somatostatin - delta cells
exocrine - acinar cells trypsinogen chyotrypsin carboxypolypeptidase proelastase pancreatic amylase lipase
what creates the bulk of the pancreas
exocrine cells - acinar cells
trypsinogen is activated by __ and converted to __
where is the activation enzyme secreted
activated by enterokinase - secreted from enterocytes
converted to trypsin
most of the water and food is absorbed where
large intestine
what produces vitamins in the large intestine
and what vitamin
bacteria produce vitamin k in large intestine
the large intestine contains many __ which secrete mucus to aid in passage of feces
goblet cells
carbs and amino acids are absorbed where
fats are absorbed where
bile salts are absorbed where
duodenum and jejenum
ileum
distal ileum
where is vitamin K produced in the GI
colon or large intestine by bacteria
water soluble vitamins are absorbed how
fat soluble vitamins are absorbed how
water soluble - secondary active transport using Na amino acid co transporters - then exit enterocytes via passive diffusion
fat soluble - same as fat
iron is absorbed where
jejunum
iron combines with __ in the blood to form __
iron combines with __ in the cells to form __
apotransferrin –> transferrin
apoferritin –> ferritin
what does transferrin do
transfers iron to liver, spleen, bone marrow
iron is released by cells to form what
hemoglobin and myoglobin
vitamin B12 and intrinsic factor form a complex that is delivered to the ____ where it is bound to __ receptors on the enterocytes and transported to portal vein
terminal ileum
cubulin receptors
what is the livers role in fat, protein, and carb metabolism
makes fat and cholesterol
builds proteins
carbohydrate metabolism
what substances and vitamins does the liver store
glycogen
vitamin A, D, and B12
what organ detoxifies toxic substances such as drugs and alcohols
liver
where does bilirubin conjugation occur
liver
what liver cells are associated with immune function
kupffer cells
what organ makes clotting factors and forms red blood cells in the fetus
liver
bilirubin is a byproduct of ___ breaking down in the ___
RBC
spleen
how long do RBCs live
120 days or 4 months
old RBCs are broken down into __ and __
heme and globin
heme is broken down into __ and __
biliverdin and iron
biliverdin is converted to __ which is carried in the blood by __
bilirubin
albumin
the unconjugated form of bilirubin is __ soluble
the conjugated form of bilirubin is __ soluble
fat soluble
water soluble
where is bilirubin conjugated in the body
bilirubin is conjugated to what by what enzyme
liver
glucoronide by glucuronyl transferase
once bilirubin is conjugated it is secreted into the ___ , where __ (bilirubin + bile salts) is released that saponifies fat to make it more digestable
gall bladder or biliary tree
bile
bilirubin in the gut is converted to what
urobilinogen
urobilinogen is converted to __ which is then excreted in the __
the rest of the urobilinogen in the gut is converted to __ which is oxidized to __ which is excreted in the __
urobilin (gives urine its color)
urine
stercobilinogen
sterobilin (gives stool its color)
stool
what percent of bile salts are reabsorbed and sent back to the liver through enterohepatic circulation
95%
what are the roles of the gall bladder?
when is bile secreted from gall bladder?
stores bile - 50 cc
concentrates bile
excretes bile when fat is present in duodenum (CCK)
what is the gall bladder controlled by
CCK - released when fat is present in duodenum
causes contraction of gallbladder which releases bile
what causes the gall bladder to contract and secrete bile
CCK
what are the endocrine secretions for the gut in charge of
gastrin somatostatin gastric inhibitory peptide CCK secretin glucagon like peptide 1 ghrelin motilin
gastrin - G cells in pyloric antrum of stomach - HCL secretion, gastric motility, delay gastric emptying - stimulated by vagal and alcohol
somatostatin - D cells in stomach and delta cells in islet of langerhans in pancreas - inhibits HCL secretion, gallbladder contraction, pancreatic secretion - stimulated by acidic PH
gastric inhibitory peptide - K cells in SI - decreases HCL secertion, increases insulin secretion - stimulated by glucose and fat in duodenum
CCK - I cells in SI - increase bile release from gallbladder, pancreatic enzymes, contraction of gall bladder, relax sphincter of oddi and lower (cardiac esophageal sphincter - stimulated by fat in duodenum
secretin - S cells in crypts of lieberkuhn in intestine - increase bicarbonate release from pancreas, decrease HCL secretion - stimulated by acidic PH
glucagon like peptide 1 - K cells in duodenum and jejunum - inhibits gastric emptying
ghrelin - P cells in stomach - increased before meals and decreased after meals - stimulates hunger
motilin - M cells in duodenum - controls cyclical movement of the gut and increases during fasting state