Histo Phys-Stomach Flashcards
What histological region of the stomach is responsible for secreting acid?
Oxyntic gland area
How many muscle layers are in the wall of the stomach?
Some say 3, really they are all intertwined to form a thick muscularis externa
Identify the region of the stomach shown below
Gastric rugae. These folds are mostly unfolded when the stomach is completely full.
Surface epithelium of the stomach
Single layer of columnar epithelium
What cells are present as you move down the gastric pits?
1) Mucous surface cells 2) Mucous neck cells 3) Parietal cells (secrete acid) 4) Peptic cells (Chief cells that secrete peptic enzymes) 5) Enteroendocrine cells
What cells are indicated below?
Parietal cells. Note that they are located within the epithelium and have a pale pink stain.
Identify the cells indicated below
Top: Chief cell. Bottom: Parietal cell
How do you tell the difference between mucous surface cells and chief cells?
The surface mucous cells will have the nucleus all the way at the base and its cytoplasm will be more pale.
Role of HCl secreted by parietal cells
Kill bacteria, denature protein, convert pepsinogen to pepsin
Role of ion secretion in stomach
Protection of mucosa (Na, K, Cl, HCO3)
Role of chief cells in stomach
Secrete pepsinogens after vagal impulse
Role of mucous secretion in the stomach
Protection of surface epithelium
Role of intrinsic factor secretion in the stomach
Absorption of vitamin B12 complex in the ileum
Role of water secretion in the stomach
Dissolving and dilution of ingested material
By what mechanism is acid secreted from the parietal cell?
Secretagogue binds receptor -> cAMP activation or inactivation -> protein kinase turned on or off -> H+/K+ ATPase turned on to pump out H+ or turned off
What happens to the actual morphology of the parietal cell when they begin to actively secrete ions?
Expansion of canaliculi. Note the many channels surrounding the mitochondria in the image below.
Ions secreted by parietal cells? Ions secreted by mucous cells?
Parietal: H+, Cl-, K+. Mucous cells: Na+, Cl-, HCO3-X
What structure is indicated below?
Surface mucous cells in the stomach. Note the elongated cells with mucus secretory granules localized apically.
How does mucous help protect the gastric epithelium?
Trefoil factors family (TFF) help ulcers heal by promoting migration of epithelium across injured areas. Mucous also contains bicarbonate (prevents acidic damage).
Cells that secrete gastrin
G-cells (endocrine) secrete the activating factor out the basilar aspect
Cells that secrete somatostatin
D-cells (paracrine) secrete the inhibitory factor
Function of ghrelin
Increase HCl and appetite
What is the role of the ECL cell in acid secretion?
Different molecules bind receptors and increase or decrease secretion of histamine (which increases acid secretion by local parietal cells).
4 phases of gastric secretion
1) Interdigestive (basal state) 2) Cephalic (sight, smell and taste) 3) Gastric (food in stomach) 4) Intestinal (food in intestine)
3 different ways we can activate parietal cells
1) Enteric nervous system activates G-cells, gastrin activates parietal cells 2) Direct activation by vagus nerve 3) Vagal activation of ECL cells that secrete histamine and activate parietal cells
2 different ways we can inhibit parietal cells
1) D cell activation, somatostatin inhibits parietal cells and ECL cells 2) Secretin release to inhibit parietal cells
Metabolic effects from prolonged vomiting
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Drugs used to decrease gastric acidity?
H2 antagonists, anticholinergics and PPIs
