Gastrointestinal tract Flashcards
there are ___ glandular regions in the stomach, but there are ____ sections of the stomach
2 glandular regions
3 anatomical sections
what are the 3 cell types of the gastric pits?
1) mucous neck cells
2) Chief cells
3) Parietal cells
which gastric pit cells produce HCl (stomach acid)?
parietal cells
in what sections of the stomach is HCl produced?
Fundus and Body
________ cells of the gastric pits will produce intrinsic factor
parietal cells
pepsinogen is produced by what type of gastric pit cells? In what sections of the stomach is pepsinogen found?
- produced by CHIEF cells
- found in body and antrum of stomach
T/F: mucous (produced by mucous neck cells) is produced throughout all sections of stomach
true
_______ cells produce HCO3- (carbonate)
Epithelial Cells
what do G cells produce? where are they found
G cells produce GASTRIN
found in Antrum of stomach
Somatostatin is produced by what cell type?
D cells
Enterochromaffin-like cells of the stomach produce what?
Histamine
_______ is the strongest HCl stimulant for the parietal cells
Histamine
what enzyme is essential for the production of HCl in parietal cells?
carbonic anhydrase
T/F: the H+/K+ transporter on parietal cells does not require ATP
FALSE
it requires ATP
T/F: the flow of Cl- ions from parietal cells happens without the need of ATP (AKA- Cl- diffuses down its concentration gradient)
True
H+ = active Cl- = passive
what is transported to the capillaries during HCL production in the stomach? what is absorbed from the capillaries?
HCO3- is transported from the parietal cells, toward the capillaries
Cl- is taken up by the parietal cells
what can trigger histamine release for parietal cells?
release can be triggered by gastrin or Ach
T/F: Gastrin and Ach can have direct effects on parietal cells
True- they cause a release of histamine which increases HCl production
what does the activation of parietal cell receptors (for Ach or gastrin) result in?
activation of receptors results in second messenger activation that increases the ability of parietal cell to release H+ and Cl-
___________ is a potent inhibitor of HCl secretion via 2 mechanisms
Somatostatin
what 2 stomach cells does somatostatin have an effect on?
inhibits both G Cells and Parietal Cells
result- decreases gastrin and HCl production
what are cephalic phase stimuli? what do they activate?
—sight, smell, taste of food
—activation of PNS and production of Ach
(also activated by mechanical stimulation from chewing and swallowing).
when the pH of chyme is < 3, _______ is produced
secretin
T/F: the intestinal phase initially enhances HCl secretion. But, later in digestion, the intestinal phase is inhibitory.
true
what triggers the “gastric phase” of digestion?
- distention, proteins, peptides and amino acids.
- Increase in gastrin secretion.
__________ is a zymogen (i.e., it is a proenzyme that needs to be cleaved to become active)
pepsinogen
T/F: pepsinogen is converted to pepsin within chief cells
FALSE
- chief cells secrete pepsinogen
- HCl in the stomach cleaves pepsinogen into pepsin
the HCl produced by the stomach would dissolve gastric tissue, but ______ provides a barrier that protects the cells
mucus
produced by mucus neck cells
what IONS are used by gastric epithelial cells?
Na+
Cl-
K+
HCO3-
“Intrinsic factor” is involved with the absorption of what?
vitamin B12
happens later on in the intestines
In general, the same factors that affect HCl secretion also affect gastric ___________
motility/emptying
__________ are hormones produced by intestinal cells that inhibit the secretion or motility in the stomach�
Enterogastrone
what are 2 examples of enterogastrones?
Secretin, and CCK
what would be the effects on stomach motility if there were an increase in duodenum acidity, or an increase in Fats/proteins?
it would DECREASE gastric emptying
Secretin (acid) and CKK (fats/proteins) would trigger the INCREASE of enterogastrones
the pancreas is an EXOCRINE gland….. what does it excrete?
bicarbonate ions
digestive enzymes (many, many, many digestive enzymes)
what converts trypsinogen into trypsin?
membrane bound enterokinases
what is the role of trypsin?
activates enzymes (from the pancreas) in the LUMEN
both trypsinogen and inactive digestion enzymes are produced by the ________
pancreas
CCK Secretion is potentiated by ______
secretin
when there is an increase in intestinal fatty acids and amino acids, the cells of the small intestine will secrete _______. how does this effect the pancreas?
CCK
it will increase the amount of enzymes produced by the pancreas (increases digestion rate)
Bicarbonate secretion is essentially the same as _____ secretion in reverse.
HCl
how is the release of bicarbonate from the pancreas regulated?
Hormone regulation by secretin
Feedback regulation by acidity
the cell of the liver secrete bile into small ducts called bile _______
canaliculi
_________ is absorbed thanks to the help of bile salts
cholesterol
what substances are found in “Bile”?
- Bile salts
- Lecithin
- Cholesterol
- Bile pigments (like bilirubin) and other metabolic end products
- Bicarbonate ions
Bile salts are recycled through what?
through the enterohepatic circulation
how much bile salt does the liver SYNTHESIZE per day? how much does it SECRETE?
synthesizes 20-60 mg of bile salts a day
what is the end feedback result of increased fatty acids in the duodenum?
increased bile flow to duodenum
Primary role of the small intestine is _______
absorption
T/F: Contractions of the small intestine are important for absorption
true
what is Peristalsis?
progressive contractions of successive sections of circular smooth muscle
what causes the Segmentation of the small intestine
closely spaced contractions of circular muscle layer
what does the segmented nature of the small intestine allow for?
for the movement/mixing of chyme/bolus through the intestines (maximizes contact)
T/F: After most absorption has occurred, segmentation contractions occur
FALSE
peristaltic contractions occur
Peristalsis is driven by what?
by a migrating myoelectric complex
peristalsis is Initiated by the intestinal hormone ______
motilin
what makes up most of the bolus in the large intestine?
small intestine secretions or undigestable foods
what is the primary purpose of the large intestine?
to actively transport Na+ from lumen to blood
Also, bicarbonate secretion is coupled to Cl- ion absorption
peristaltic-like contractions of the LARGE intestine occur how often?
3 – 4 times per day
what is absorbed by the small intestine?
carbohydrates, proteins, fats, vitamins, minerals
