GI 3 Part 2 Flashcards
How many litres of food, drink, saliva enter stomach each day
3.5 litres
Stomachs 3 general functions
- Storage
- Digestion
- Defence
What is storage in stomach for
To regulate passage into small intestine
What is digestion in the stomach
Chemical and mechanical digestion into chyme using peristaltic contractions
What does defence do in stomach
Destroys bacteria and other pathogens in food and other pathogens trapped in airway mucus (mucocilliary escalator)
What is reinforced in stomach
Motility and secretion that was initiated during cephalic phase is driven by distension
What enhances motility and secretions in the stomach
Distension
Upon swallowing food what makes room in stomach for food
Parasympathetic neurons to ENS cause fundus of stomach to relax (receptive relaxation)
What causes motility in stomach
Weak peristaltic waves (15-25 secs) that increase in force proceeding down antrum moves chyme toward pylorus (propulsion) and then larger particles are moved back to body (retropulsion)
What does the peristaltic contractions in stomach cause
Mixes food with acid and digestive enzymes, small amounts of chyme squeeze through pylorus
What do gastric secretions do
Protect and digest
How are gastric secretions released with short reflex
G-cells release gastric (hormone) in response to amino acids, peptide, and distension
What is long reflex of how gastric secretions released
Parasympathetic neurons to ENS and stimulate gastric production during cephalic phase
How does gastrin directly stimulate gastric secretions
Stimulates gastric acid production and secretion directly from parietal cells
What reflex for gastric secretions comes first
Long reflex and then short reflex causes further when food enters stomach
How does gastrin indirectly stimulate parietal cells
Stimulates histamine release from enterochromaffin-like cells (ECL) which stimulates parietal
Where is acid secretion from
Parietal cells
How much gastric acid (HCl) produced daily
1-3 L with pH as low as 1
What is parietal cells stimulated by
- gastrin from Gcells
- histamine from enterochromaffin-like cells
- ACh from ENS neurons via long and short reflexes (during cephalic)
What are 5 gastric acid functions
- Stimulated release of Pepsinogen from chief cells, cleaves pepsinogen to pepsin
- Denatures proteins making easier for pepsin
- Kills bacteria and other ingested microorganisms
- Inactivates amylase from saliva
- Stimulates D cells to release somatostatin
What does pepsin do
Digest proteins
