3a. Gastric Acid Secretion CAMTASIA Flashcards
Generally, functions of the stomach?
It functions primarily as a reservoir to store large quantities of recently ingested food, thus allowing intermittent feedings, initiating the digestive process, and releasing its contents in a controlled fashion downstream to accommodate the much smaller capacity of the duodenum.
What are the 2 types of mucosa in the stomach?
Where is each located/what does each do?
- oxyntic gland mucosa: secretes acid, located in prox stomach (body, fundus).
- pyloric gland mucosa (antrum). secretes gastrin

what are the 5 layers of the stomach lining?
in what layer are all the functional secretory elements?
- mucosa (contains secretory elements)
- deep mucosa/lamina propria
- submucosa (connective tissue of collagen and elastin)
- muscularis propria
- serosa
Parietal/Oxyntic glands of the fundus: what cell types do they contain?
- surface mucus cells
- mucus neck cells
- parietal cells
- chief cells
- enterochromaffin-like cells

oxyntic glands: what do they secrete?
anatomy of the glands?
location?
- acid, intrinsic factor, most gastric enzymes
- straight, simple tubular glands
- located in fundus/body
anatomy of an oxyntic gland: what are the important areas/what cell types are located there?
each gland has 3 areas: isthmus, neck, base
Isthmus: surface mucous cells
Neck: parietal and mucous neck cells
Base: chief cells
Scattered throughout: D cells (somatostatin), enterochromaffin cells (histamine)

what is the process of creating these gastric exocrine cells? where do they start/where do they migrate?
- Start as stem cells (precursor cells above) in the midregion or neck of the gastric glands.
- Upward flow of the neck cells toward the surface is a rapid process, < 1 week, –> mucus cells
- Downward flow of neck cells into the gastric gland may require several weeks –> parietal cells and chief cells.

Motor functions of the stomach?
- reservoir for ingested food
- digestion: mixing, grinding, pepsinogen secretion (initial protein digestion)
- Empties into duodenum once particles are 50microns in size
What is the cephalic phase? what are the things that happen during this phase?
First phase of acid secretion
Cephalic = initial response to sight, smell, taste, thought of food
-Vagally mediated via direct stim of parietal cells & ECL cells; indirect stim of G cells
What is the gastric phase? what happens during this phase?
second phase of acid secretion in response to a meal
- distension
- buffering of gastric acid pH
- AA stimulation of the parietal cells and G cells
what is the intestinal phase? what happens?
third phase of acid secretion in response to a meal
- response to movement of food out of the stomach/low pH
- chyme components in duodenum w release of secretin & GIP
Cardia: begins at what location (anatomically)?
transition from what cell type to what?
what is function?
gastric pits are deep or shallow?
- begins at Z line
- transition from Squamous to Columnar (at GEJ)
- Protects surface of the stomach from corrosive gastric contents, prevents reflux
- Shallow gastric pits

Fundus/body
what is function?
gastric pits are deep or shallow?
what cell type?
- Accomodation of food
- Gastric acid secretion
- Deep gastric pits – parietal cells, chief cells, endocrine cells (ECL, D cells)
Antrum:
function?
gastric pit depth? cell types?
Mixing, grinding, sieving particles
Regulation of gastric secretory function via gastrin/somatostatin
-Gastric pits are intermediate: surface and neck mucus cells, endocrine cells (G cells, D cells)
LES and cardia: secretions?
Mucus
HCO3
Fundus and body: secretions?
H+
Intrinsic factor
mucus
HCO3
pepsinogens
lipase
antrum and pylorus: secretions?
mucus
HCO3
surface cells and neck cells: product? function?
mucus, HCO3, trefoil peptides
lubrication, protection
parietal cells: product? function?
H+, intrinsic factor
protein digestion, binding of cobalamin, protection from bacteria
chief cells: product? function?
pepsinogen, gastric lipase
Protein digestion, triglyceride digestion
endocrine cells: product? function?
gastrin (G cell), histamine (ECL cell), somatostatin (D cell)
regulation of acid secretion
what is a pareital cell? where is it located? what does it produce? what does it require?
Principle cell in oxycintic portion.
produces gastric acid
requires energy to concentrate H ions, gets it from ATP produced from mitochondria wihtin the cell

Describe the parietal cell in its resting state.

- Resting state: the cytoplasm of the parietal cells is dominated by numerous tubulovesicles.
- An intracellular canaliculus is continuous with the lumen of the oxyntic gland.
- Resting state: canaliculus is collapsed.
- Low flow of acid (note only one yellow pump on the canaliculus)

Parietal cell: what happens with stimulation?
After stimulation of acid secretion the tubulovesicles become microvilli and project into the canaliculus, which has become greatly expanded to occupy much of the cell.
Exchanges H for K and creates HCl which is released into the lumen
Carbonic anhydrase and H,K,ATPase (enzymes for the production and secretion of acid), are localized in the microvilli.
The activities of these enzymes increases dramatically during acid secretion. Acid secrtion begins within 10 minutes of administering a stimulant.









