Gastric secretion and its regulation Flashcards
types of secretion - 1
HCl
- secreted by parietal cells of stomach
- creates acidic environment in stomach to kill pathogens entering
- to activate pepsinogen -> pepsin for protein digestion
types of secretion - 2
intrinsic factor
- secreted by parietal cells
- needed for absorption of vitamin B12 in small intestine
types of secretion - 3
pepsinogen
secreted by chief cells
by converting pepsinogen -> pepsin to help break down proteins
types of secretion - 4
mucus
- produced by mucosa/ goblet cells
protection
movement
lubrication
types of secretion - 5
bircarbonate
released by epithelial cells
neutralises stomach acid
Phases of Gastric Secretion - 1
DETECTION
the thought / sight/ smell of food causes activation
signals sent vagus nerve
signals sent to medulla/pons in brainstem
Ach + Muscarinic Receptors
- parietal cells released HCl
- chief cells release pepsinogen
Phases of Gastric Secretion - 2
STORING
when fundus/ corpus stomach receives food it temporarily stores it
the stomach can expand if there is large amount of food to be stored due to rugae + vagovagal stretch receptors
G-cells release gastrin
enterochromaffin cells release histamine
Phases of Gastric Secretion - 3
MIXING
food mixed with stomach 3 layers:
- longitudinal = outer
- circular = medial
- oblique = inner
this forces contents to be mixed with gastric juices + gastric enzymes = chyme produced
Phases of Gastric Secretion - 4
EMPTYING
the end of the stomach is pars pylorica which stretches into small intestine
inhibitory hormones ensures negative feedback mechanisms to ensure chyme is ready to move from stomach -> SI
Regulation of the stomach emptying - hormone 1
GASTRIN = stimulates
produced by G cells in stomach
producing of gastric acid for motility
Regulation of the stomach emptying - hormone 2
CCK = inhibits
produced by small intestines
released to slow gastric emptying as an inhibition
Regulation of the stomach emptying - hormone 3
SECRETIN
produced by S cells of duodenum
released to slow gastric emptying as an inhibition
Regulation of the stomach emptying - hormone 4
GASTRIC INHIBITORY PEPTIDE
released by small intestine
release insulin in response to food intake
Regulation of the stomach emptying - hormone 5
MOTILIN = stimulates
released during fasting state
promotes migrating motor complex MMC
Regulation of the stomach emptying - reflex mechanism
enterogastric reflex
if chyme is too acid/ fatty/ osmolaric OR small intestine is overstretched
gastric motility inhibited
