Duodenum, Pancreas and Bile Flashcards
Gastric Emptying
Motility organised to achieve orderly emptying of contents from stomach to duodenum
Emptying requires the mixing of food with gastric secretions
Caused by peristaltic contractions of antrum
Opposed by the pylorus
Strong contractions begin in mid stomach and spread to caudad region
As stomach empties contractions move up
6X more powerful than normal
Each strong wave forces chyme into duodenum when plyoric tone normal
Mixes stomach contents & provides the plyoric pump
Plyorus has a thickened region of circular muscle, plyoric sphincter
Usually shut
Open just enough to allow fluids to leave stomach
Allows chyme to leave when it has a fluid consistency
Sphincter influenced by both nerves & hormones
Duodenum has most control
Ensures that chyme entering the duodenum at an appropriate rate
Gastric emptying promoted by extra stretch on stomach wall
Activates reflexes to relax the sphincter
Enterogastric reflexes - gastric emptying
Powerful duodenal nervous reflexes
Inhibits stomach emptying
Signals go back to stomach if volume of chyme too much for duodenum to handle via;
- enteric nervous system in gut wall
- prevertebral sympathetic side chain
- vagus nerve
Inhibit plyoric pump & increase sphincter tone
Inhibitory enterogastric reflexes influenced by;
- distension in duodenum
- irritation of duodenal mucosa
- acidity of duodenal chyme
- osmolarity of the chyme
- presence of certain breakdown products i.e. proteins & fats
