GI structure and function Flashcards
Breaks down ingested food
Prepares food for uptake by the body’s cells
Provides body water
Eliminates wastes
Controlled by hormones and the autonomic nervous system (except for chewing, swallowing, and defecation)
functions of the GI tract
4 layers of GI tract from deep to superficial
Mucosa
Submucosa
Muscularis
Serosa or adventitia
enteric plexus layers
Subserosal plexus
Submucosal plexus
Myenteric plexus
ENS functions
egulates gastrointestinal motility, secretory activity, vascular activity, and inflammation
Approx 100 million neurons located within numerous small ganglia.
ENS
Myenteric plexus location
between longitudinal and circular smooth muscle layers
what does the myenteric plexus regulate
motor activity of the gut
submucosal plexus location
between the circular smooth muscle and submucosa
what does the submucosal plexus regulate
mucosal functions
The two types of receptors in the gut that are sensitive to acetylcholine
Muscarinic acetylcholine receptors
Nicotinic acetylcholine receptors
The key neurotransmitter used in the SNS
NE
what does NE act on
alpha and beta adrenergic receptors
excitatory Nonadrenergic/noncholinergic NTs
Substance P, neurokinin A
inhibotory Nonadrenergic/noncholinergic NTs
NO, vasoactive intestinal polypeptide
The two principal muscle layers that control motility of the GI tract are:
the inner circular layer muscularis externa
the outer longitudinal layer of the muscularis externa
this layer of the GI smooth muscle is thickened for form sphincters
the outer longitudinal layer of the muscularis externa
what type of muscle is most of the GI
smooth
Reservoir for chewing and mixing of food with saliva
mouth
what does the mouth contain
taste buds, olfactory nerves, and teeth
Submandibular
Sublingual
Parotid
salivary glands
saliva consists of
Water with mucus, sodium, bicarbonate, chloride, potassium, and salivary α-amylase (carbohydrate digestion)
what is saliva controlled by
sympathetic and parasympathetic fibers
location of swallowing center
reticular formation of the brainstem, insula/claustrum and cerebellum
phases of swallowing
Oral and pharyngeal phases
Esophageal phase
what does the esophagus consist of
epithelial cell layer
inner layer of circular muscle
myenteric nerve plexus
outer layer of longitudinal muscle.
hollow tube (25–30 cm long, 2–3 cm wide).
esophagus
what is the esophagus delimited by
UES and LES
what is the UES made of
striated circular muscle
what is the LES made of
smooth muscle
are sphincters closed or open btwn swallows
closed
why are the sphincters closed btwn swallows
Prevents entry of air and gastric acid into the esophagus.
controls the passage of digesta into the stomach
prevents the reflux of gastric contents into the esophagus
Contracted between swallows
Relaxed during swallows
LES
peristalsis
waves of relaxations and contractions of the tunica muscles
A hollow, muscular organ that stores food, secretes digestive juices, mixes food with the juices, and propels partially digested food (chyme)
stomach
muscle layers of stomach
longitudinal, circular, and oblique
gastrin
increase gastric and intestinal motility
secretin
inhibits gastrin release and gastric acid secretion
cholecystokinin
satiety
motillin
Increases gastric emptying and small bowel motility
what gastric juices does the stomach secrete
Mucus, Acid, Enzymes, Hormones, Intrinsic factor, Gastroferrin
what do pit/surface/foveolar cells secrete
mucus
what do mucus neck cells secrete
mucus
what do parietal cells secrete
HCl, intrinsic factor
what do zymogenic chief cellls secrete
pepsinogen
where are parietal cells and chief cells located
fundus of stomach
what do G cells secrete
gastrin
3 phases of gastric secretion
cephalic, gastric, and intestinal
cephalic phase of gastric secretion
anticipation (sight/smell of food) stimulates the vagus
gastric phase of gastric secretion
when food hits the stomach
intestinal phase of gastric secretion
slowing down
what do Enterochromaffin-like cells secrete
histamine
what does histamine stimulate
acid secretion
what is histamine stimulated by
gastrin secretion
what do D cells stimulate
somatostatin
what does somatostatin inhibit
Inhibits acid, pepsinogen, and gastrin secretion
outer layer of SI
longitudinal
inner layer of SI
circular
microvilli are found here
brush border
fat digestion begins here
SI
presence of food in the stomach and gastric peristalsis stimulates this
gastroileal reflex
inhibition of gastric motility by distention of the ileum stimulates this
ileogastric reflex
what does the ileocecal valve do
Separates small from large intestine; limits reflux of colonic contents into the ileum
rectosigmoid sphincter
O’Beirne sphincter
Internal anal sphincter is made of this
smooth muscle
external anal sphincter is made of this
skeletal muscle
Taenia coli
Longitudinal ribbons of smooth muscle
______ are 95% of the fecal flora in the colon
Anaerobes
what separates lobes of the liver
falciform ligament
Caudate and quadrate lobes are part ofthis lobe in the liver
right
Immune cells in the liver
Kupffer cells
Stellate cells
Pit cells
what does bile contain
bile salts, cholesterol, bilirubin, electrolytes, and water
what is bile formed by
hepatocytes
where is bile secreted into
bile canalibuli
what is Enterohepatic circulation responsible for
recycling of bile salts
this is a byproduct of the destruction of aged red blood cells
bilirubin
functions of liver
store blood, remove bact. and foreign particles, make clotting factors, make bile, metabolize fats/proteins/carbs, detox, store vitamins and minerals
A sac-like organ that lies on the inferior surface of the liver
gallbladder
function of gallbladder
store and concentrate bile between meals
how much bile does the gallbladder hold
90 mL
