The Stomach and Regulation of Gastric Activity

the stomach is the

distensible pouch that serves as a reservoir for ingested food

the pyloric sphincter is the

guarded entrance into the duodenum

the pyloric sphincter is usually

opened just a tiny bit

a pylorspasm occurs most often

in infants

a pylorspasm is when

the pyloric sphincter does not relax properly

a pylorspasm results in

vomiting to relieve pressure of stomach contents

pyloric stenosis is

the narrowing of the pyloric sphincter

pyloric stenosis causes

the chyme to not be able to leave the stomach, resulting in projectile vommiting

pyloric stenosis can be caused by

a stomach ulcer

the mucosa of the stomach is made of

simple columnar epithelium

the mucosa of the stomach forms

gastric glands located in pits

surface mucous cells

secrete mucus

mucous neck cells

secrete mucus

chief cells

secrete pepsinogen and gastric lipase

G cells

secrete gastrin (hormone)

G cells are also known as

enteroendocrine cells

parietal cells secrete

intrinsic factor, H+ and Cl-

what is the function of intrinsic factor

absorption of B12

the submucosa is made of

areolar connective tissue and has many blood vessels

the muscularis is

3 layers of MT: oblique, circular and longitudinal

the serosa of the stomach is made of

simple squamous ET and areolar CT

the serosa makes up

the visceral peritoneum

the serosa becomes as it extends up towards the liver

the lesser omentum

the serosa becomes the at the greater curvature

the greater omentum

the greater omentum

hangs over the intestines

when food enters the stomach

peristalsis begins

peristalsis

pushes chyme towards the plyorus

during peristalsis some chyme is and the rest is ____

pushed through the pyloric sphincter and the rest is forced back to the body of the stomach, so that the mixing action continues

as chyme is moved bac and forth within the stomach

it mixes with enzymes

when lingual lipase enters the stomach

it is activated

gastric lipase

breaks down triglycerides into fatty acids and glycerol

what does HCl do to proteins

it denatures them

HCl stimulates

the secretion of bile and pancreatic juices

HCl converts

pepsinogen into the active form of pepsin

pepsin

enzyme that breaks down proteins in the stomach

mucous secreted by surface cells and neck cells

protects the stomach lining from damage

describe the absorption in the stomach

little absorption except alcohol, aspirin and H2O

what occurs during the cephalic phase

sight, thought, smell of food activates the parasympathetic nervous system

describe the pathway of communication during the cephalic phase

hypothalamus -> medulla -> excites parasympathetic nervous system -> increases gastric gland activtity

what is the function of the cephalic phase

prepares the stomach to receive food

the gastric phase refers to what happens

as the stomach accepts food

what things happen as the stomach accepts food

stretch receptors and chemoreceptors are activated

chemoreceptors are activated during the gastric phase

as pH increases due to protein digestion

stretch receptors and chemoreceptors triggers

reflex of submucosal and myenteric plexus which activates the parasympathetic nervous system

in the gastric phase, activation of the parasympathetic nervous system leads to

-peristalsis
-increased activity of chief, parietal and mucous cells
-release of Ach and histamine

the release of Ach during the gastric phase

stimulates the release of gastrin by G cells

gastrin increases

motility of the stomach and secretions of parietal and cheif cells

effect of gastrin on the pyloric sphincter

relaxes it

effect of gastrin on the lower esophageal sphincter

strengthens the contraction of it

gastrin is controlled by

negative feed back

gastrin release is inhibited at

pH of 2

histamin is released by

mast cells in the lamina propria as the stomach wall distends

histamine acts with

ACh and gastrin to increase activity of parietal cells

parietal cells have receptors for

ACh, gastrin, histamine

antacids block

histamine-2 (H2) receptors

the blocking of histamine-2 (H2) receptors

decreases H+ secretion

the hormonal response of the intestinal phase begins as

chyme enters the duodenum

the pH of chyme is

low (leass than 4.5)

the low pH of chyme

stimulates duodenal cells to release secretin

secretin decreases

gastric secretions of parietal and chief cells

secretin activates

the pancreas and the liver

amino acids and triglycerides present in chyme stimulate

release of cholecytokinin (CCK) fron enteroendocrine cells in duodenum

CCK

inhibits gastric secretions and decreases strength of contraction

what is a choleecystectomy

a gallbladder removal

CCK promotes

contraction of pyloric sphincter

CCK inhibits

stomach emptying

CCK controls

the rate so that the duodenum is not overloaded

a high fat meal

stays in the stomach longer

presence of partially digested proteins in the duodenum stimulates

the release of gastrin from duodenal cells

the partially digested proteins in the duodenum stimulating the release of gastrin from duodenal cells

increase acid production so that the stomach can meet specific requirements of meal

the neural response of the intestinal phase involves the

enterogastric reflex

what is the enterogastric reflex

presence of chyme in duodenum activates stretch receptors within the duodenum

presence of chyme in duodenum activating stretch receptors within the duodenum

stimulates the medulla

sympathetic impulses

inhibit gastric activity

what things work to decrease motility

CCK, secretin, and the sympathetic nervous system

when motility is decreased

gastric secretions and the force of contraction are inhibited

describe what occurs during vommiting

irritants (drugs, toxins, motion, emotion) -> medulla -> esophageal sphincters open as the abdominal muscles and the diaphragm push on the stomach -> contents exit

the hormonal response of the intestinal phase involes

secretin, gastrin and CCK