Gastrointestinal tract Flashcards by asw asw

there are ___ glandular regions in the stomach, but there are ____ sections of the stomach

2 glandular regions

3 anatomical sections

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what are the 3 cell types of the gastric pits?

1) mucous neck cells
2) Chief cells
3) Parietal cells

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which gastric pit cells produce HCl (stomach acid)?

parietal cells

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in what sections of the stomach is HCl produced?

Fundus and Body

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________ cells of the gastric pits will produce intrinsic factor

parietal cells

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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

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T/F: mucous (produced by mucous neck cells) is produced throughout all sections of stomach

true

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_______ cells produce HCO3- (carbonate)

Epithelial Cells

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what do G cells produce? where are they found

G cells produce GASTRIN

found in Antrum of stomach

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Somatostatin is produced by what cell type?

D cells

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Enterochromaffin-like cells of the stomach produce what?

Histamine

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_______ is the strongest HCl stimulant for the parietal cells

Histamine

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what enzyme is essential for the production of HCl in parietal cells?

carbonic anhydrase

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T/F: the H+/K+ transporter on parietal cells does not require ATP

FALSE

it requires ATP

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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

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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

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what can trigger histamine release for parietal cells?

release can be triggered by gastrin or Ach

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T/F: Gastrin and Ach can have direct effects on parietal cells

True- they cause a release of histamine which increases HCl production

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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-

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___________ is a potent inhibitor of HCl secretion via 2 mechanisms

Somatostatin

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what 2 stomach cells does somatostatin have an effect on?

inhibits both G Cells and Parietal Cells

result- decreases gastrin and HCl production

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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).

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when the pH of chyme is < 3, _______ is produced

secretin

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T/F: the intestinal phase initially enhances HCl secretion. But, later in digestion, the intestinal phase is inhibitory.

true

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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 secretes 1,200-3,600 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