Case 2 - yaffas Flashcards
how is the stomach divided physiologically
orad portion - first 2/3 of the body
caudad portion - last 1/3 of the body
explain of the storage function of the stomach works
food entering forms concentric circles of food in the orad portion of the stomach
the newest food is closest to the oesophageal opening, whilst the old food lies nearest the outer wall of the stomach
when this food stretches the stomach wall, a vagovagal reflex occurs
signals are sent from the stomach to the brainstem and back, reducing the muscle tone of the muscular wall of the body of the stomach so that the wall can expand outwards progressively
what is the max volume of the stomach
0.8-1.5 litres
what are digestive juices of the stomach secreted by
the gastric glands whcih are present in almost the entire wall of the body of the stomach except along the lesser curvature of the stomach
what do these digestive juices come into direct contact with
the food lying against the mucosal surface of the stomach
explain the mixing of the stomach contents
as long as food is in the stomach, weak peristaltic constrictor waves, called mixing waves begin in the mid to upper portions of the stomach wall and move toward the antrum about once every 15 seconds
what are these waves initiated by
the gut wall basic electrical rhythm, consisting of slow waves that occur spontaneously in the atomach wall
what happens as the constrictor waves progress from the body into the antrum
they become more intense
what do these extremely intense waves provide
powerful peristaltic action potential driven constrictor rings that force the antral contents under higher and higher pressure towards the pylorus
what is an exceedingly important mixing mexhanism in the stomach
the moving peristaltic constrictive ring, combined with this upstream squeezing action called retropulsion
what is the upstream squeezing action
the antral contents are squeezes upstream through the peristaltic ring toward the body of the stomach and not through the pylorus
what is chyme
the mixture of food that passes down the gut, after it has been mixed with the stomach secretions
what do the peristaltic waves do
cause mixing in the stomach
provide a pumping action called the pyloric pumo
what is the pylorus
the distal opening of the stomach
what does stretching of the stomach wall elicit
local myenteric reflexes in the wall that greatly accentuate activity of the pyloric pump and at the same time inhibit the pylorus
where are the G cells that secrete gastrin found
the antral mucosa
what are the duodenal reflexes that inhibit stomach emptying mediated by
directly from the duodenum to the stomach through the ENS in the gut wall
through extrinsic nerves that go to the prevertebral sympathetic ganglia and then back through inhibitory sympathetic nerve fibres to the stomach
through the vagus nerve to the brainstem, where they inhibit the normal excitatory signals transmitted to the stomach through the cvagi
what do these pathways do
strongly inhibit the pyloric pump propulsive contractions
increase the tone of the pyloric sphincter
what is cholecytokinin CCK
the hormone that has the most potent effect in regards to hormonal feedback to inhibit gastric emptying
where is CCk released and when
released from the duodenal and jejunal mucosa in response to fatty substances in the chyme
what does it act as
an inhibitor to block increased stomach motility caused by gastrin
what is secretin
released from duodenal mucosa (S cells in the crypts of Lieberkuhn)
released in response to gastric acid passed from the stomach through the pylorus