The Stomach Flashcards
the stomach is
a hollow, J shaped portion of the alimentary canal and it is located beneath the diaphragm
the cardia is
a small area of the stomach near the lower esophageal sphincter
the fundus is
the dome shaped region of the stomach superior to the cardia
the main part of the stomach is the
body
epmty volume of stomach is about
50 mL but it can hold between 1.0 and 1.5 L of material after a typical meal; max cap is almost 4.0 L
the pyloric region is
a narrow region below the body of the stomach and it is sub-divided into the antrum and the pyloric canal
stomach is separated from small intestine by
powerful pyloric sphincter
+ogen suffix means
substance is inactive
the gastric mucosa is composed of
simple columnar epithelium, which contains many globlet cells that produce a surface layer of alkaline mucus above a layer of bicarbonate-rich fluid
gastric mucosa contains
many deep gastric pits, which lead into tubular gastric flands, which secrete gastric juice
mucous surface cells and mucous neck cells secrete
thin, soluble mucus
parietal cells secrete
hydrochloric acid and intrinsic factor
chief cells secrete
pepsinogen and small amounts of gastric lipase
enteroendocrine (G) cells secrete
hormones and paracrines (local hormones)
the gastric submucosa is composed of
areolar connective tissue and combines with the mucosa to form longitundinal gastric rugae when the stomach is empty
the gastric muscularis has ____ layers of smooth muscle rather than _____
has 3 layers instead of 2
the third layer of the gastric muscularis is
oblique which allows stomach to mix, churn, and propel food through GI tract
the gastric serosa is part of
the visceral peritoneum and it helps form the omenta
within minutes after food enter the stomach,
peristaltic movements begin to churn the food and mix it with gastric juice to form chyme
gastric juice contains
hydrochloric acid, which gives it a pH as low as 0.8
hydrochloric acid is formed during
a chloride shift that exchanges bicarbonate ions that are formed in parietal cells for chloride ions that present in blood plasma
hydochloric acid accumulates in
stomach while bicarbonate ions accumulate in blood
hydrochloric acid kills
microbes in food
hydrochloric acid breaks down
collagen fibers in meat and plant cell walls
hydrochloric acid removes
amino acids from pepsinogen to convert it into pepsin
pepsin breaks
complex dietary proteins into shorter peptide chains
pepsin catalyzes the converstion of
pepsinogen into more pepsin?????????????????
gastric lipase from chief cells combines with
salivary amylase to break down a small amount of dietary fat
intrinsic factor from parietal cells is needed by
the small intestine to absorb vitman B12
***intrinsic factor is not a digestive substance because its an absorption substance
vitamin B12 is needed to make
hemoglobin; lack of intrinsic factor can lead to development of pernicious anemia
the wall of the stomach is impermeable to
most materials so absorption is limited
things that are absorbed through stomach
alcohol, aspirin, and some lipid-soluble drugs
gastric function is regulated by
neural and hormonal mechanisms
neural mechanisms involve
parasympathetic actions of vagus nerve, as well as sympathetic actions of other nerves that decrease stomach activity
hormonal mechanisms involve
gastrin
the cephalic phase is initiated by
taste, sight, smell, or thoughts of food
cerebral cortex and hypothalamus send signals to
medulla oblongata which transmits them along vagus nerve to submucosal nerve plexus
parasympathetic signals increase
stomach motility and stimulate gastric glands to secrete gastric juice
the presence of food in the stomach initiates
the gastric phase
the gastric phase
mixes food with gastric juice to form chyme
stretch receptors in stomach wall are activated and
parasympathetic signals trigger peristalsis
chemoreceptors monitor
pH of chyme and stimulate parasympathetic fibers to release acetylcholine which stimulates secretion of gastrin
gastrin triggers parietal cells to secrete
hydrochloric acid and intrinsic factor
gastrin triggers chief cells to secrete
pepsinogen
secretions caused from gastrin relax
sphincters that regulated movement of chyme out of stomach
gastrin secretion is inhibited when
pH of gastric juice falls below 2.0
histamine acts
synergistically with acetylcholine and gastrin to stimulate parietal cells to release more HCl
chyme gets released from stomach by
gastric emptying
gastric emptying typically takes about
4 hours depending on type of meal
meals high in carbs or primarily liquid will
take less time
meal high in fat content will
take more time
the movement of chyme out of the stomach through the
pyloric sphincter and into the small intestine initiates the intestinal phase
presence of fatty acids and partially digested proteins in duodenum triggers
enterogastric neural reflex, which inhibits gastric emptying
presence of chyme in the duodenum stimulates
enteroendocrine cells to release hormones that will affect stomach——–
secretin
decreases gastric secretions
cholecystokinin (CCK)
inhibits gastric emptying
gastric inhibitory peptide (GIP)
suppresses gastric secretion and motility
pyloric sphincter contracts tightly to
limit amount of chyme that enters small intestine
vomiting is the
forcible expulsion of stomach contects through the mouth
during vomiting the diaphragm
and abdominal muscles contract and squeeze the stomach, which expels its contents through open esophageal sphincters
vomiting is often preceded by
nausea and retching because lower esophageal sphincter relaxes and stomach and duodenum contract
vomiting can be triggered by
distension of stomach or by irritation from bacterial toxins, alcohol, or drugs
vomiting can also by triggered by
pelvic trauma, intense pain or repulsive or horrifying sights and or smells
prolonged vomiting is dangerous because
gastric juice and fluids are lost whic leads to additional fluid loss and acid/base imbalances
