Gastric Digestion (lec 3) Flashcards
Orad of stomach is?
top
orad means “near the mouth”
Receptive Relaxation is?
VIP induced Vagovagal reflex
distension of low esophagus relaxes LES and orad
Stomach Body Wall structure? (3 structures)
Gastric Pits: duct opening in epithelial-lined mucosa
Gastric Glands: empty into ducts
Epithelial Lining: produces alkaline mucous
Gastric Glands made of what cell types? (2)
Parietal: secrete HCl and IF
Chief: secrete pepsinogen
Antrum of stomach is?
distal end, pyloric part
Stomach Antrum made of?
pyloric glands
Pyloric glands made of what cell types?
G cells: secrete gastrin into circulation
Mucous neck cells: secrete alkaline mucous, HCO3- and pepsinogen
Components of gastric secretion and purpose? (4)
1) HCl: activates pepsin, digests protein, kills bacteria
2) IF: vit B12 absorption in ileum, indispensible!
3) Pepsinogen/Pepsin: digests proteins
4) Mucus: lubrication, acid protection
What 2 components of gastric juices initiate protein digestion?
HCl and pepsinogen
Process of HCl secretion? (slide 12)
Parietal Cell forms H+ and HCO3-
H+ out into lumen / K+ in from blood via ATPase (blocked by omeprazole),
Cl- (thru Cl- channel) follows H+ into lumen,
makes HCl
K+ channel immediately pumps K+ from cell into lumen
HCO3- into blood via Cl- exchange (alkaline tide)
HCl secretion controlled by?
Gastrin (ECL cells -> histamine -> parietal cells) (blocked by cimetidine)
PNS (ACh -> parietal cells) (Blocked by atropine)
Gastrin fxn? (3)
stim acid and pepsin secretion
stim growth of gastric and intestinal mucosa
Stim antral and intestinal motility
Gastrin released from?
In response to?
from G cells of antrum when stim by:
1) peptides/AA in stomach
2) distention of stomach
3) vagus
HCl release inhibited by? (5)
somatostatin prostaglandins pH < 3 chyme in duodemum (CCK, GIP) atropine
Gastrin stimulates parietal cells how?
thru enterochromaffin-like cells (ELC):
gastrin stims ELC to release histamine ->
Histamine stims H2-receptors on parietal cells
(inhibited by Ranitidine/cimetidine)
Gastrin ALSO stim production of more parietal cells