GI Physiology Flashcards
Inner most layer of GI wall composed of epithelial cells specialized for absorption and secretion.
mucosa
Layer of GI wall that consists of collagen, elastin, glands, and blood vessels
submucosa
Layers of GI wall that provides motility for GI tract
Circular and Longitudinal Smooth Muscle
Outer most layer of GI wall
serosa
breaking food in small particles so they are easily broken down by enzymes. occurs in the mouth and stomach
mechanical digestion
Enzymes in mouth that helps digest carbs and lipids
amylase (carbs) and lipase (lipids)
First step of swallowing
cricopharyngeal relaxation
What is different about the layers of the esophagus compared to the rest of the GI tract?
no serosa
Enzymes that breakdown proteins in the stomach
pepsin and peptidase
What are the three phases of digestion?
cephalic, gastric, intestinal
Stimulates the release of pancreatic juice and weak contractions of the gallbladder during the cephalic and gastric phases of digestion
vagus nerve
What induces the release of cholecstokinin?
fatty, protein-rich chyme
What induces the release of secretin by the enteroendocrine cells of the duodenal wall?
acidic chyme
What induces the release of pancreatic juice?
CCK and secretin
Required for the absorption of B12
intrinsic factor
Protects gastric mucosa from HCl
mucus
Cells found in the body of the stomach that secrete pepsinogen
chief cells
Cells found in the body of the stomach that secrete HCl and intrinsic factor
parietal cells
Secreted by G cells in stomach in response to eating. Stimuli include proteins, distention of stomach, and vagal stimulation
gastrin
Promotes H+ secretion by gastric parietal cells. Stimulates growth of gastric mucosa
gastrin
Released from vagus nerve. Binds to receptors on parietal cells. Produces H+ secretion by parietal cells. Atropine blocks muscarinic receptors on parietal cells
ACh
Released from mastlike cells in gastric mucosa. Binds to H2 receptors on parietal cells. Produces H+ secretion by parietal cells
histamine
Most common cause of upper GI bleeding?
duodenal ulcers
Type of motility where circular muscle contracts sending chyme in both directions. Intestine then relaxes allowing chyme to merge back together
segmentation
Type of motility where longitudinal muscle contracts propeling chyme along small intestine. Simultaneously, portion of intestine caudal to bolus relaxes
peristaltic
Controls contractile, secretory, and endocrine functions of GI tract. Sends information directly to smooth muscle, secretory, and endocrine cells
Intrinsic Innervation
Name for the numerous openings of gastric mucosa where the gastric glands empty into
gastric pits
Largest internal organ
liver
Supplies majority of blood supply to the liver. Brings venous blood rich in nutrients from digestive tract. High blood flow
hepatic portal vein
Name of structures where hepatocytes are in contact with blood in the liver. They fxn as capillaries and are arranged to form functional units (lobules)
sinusoids
Found in people who abuse alcohol because alcohol suppresses citrate cycle and thereby impairs gluconeogenesis from aminoacids.
hypoglycemia
What is the majority of cholesterol in the liver converted into?
bile salts
Necessary for digestion and absorption of lipids in small intestine. Emulsify lipids to prepare them for digestion
Bile salts
Detectable when the total plasma bilirubin > 2mg/dl
jaundice
good diagnostic test for obstructive jaundice
conjugated bilirubin
What is the pathophysiologi mechanism behind the development of varices and ascites associated with cirrhosis?
Cirrhosis leads to scar tissue which can obstruct blood and bile flow. Obstruction of hepatic venous blood flow can increase pressures
Main duct (Wirsung) runs the entire length of pancreas. Joins CBD at the ampulla of Vater
pancreatic duct
Acts on the acid producing parietal cells and indirectly decreases stomach acid production by preventing release of gastrin, secretin and histamine.
somatostatin
only digestive enzyme secreted by the pancreas in an active form
functions optimally at a pH of 7. hydrolyzes starch and glycogen to glucose, maltose, maltotriose, and dextrins
amylase
Finger-like projections of the small intestinal mucosa
villi
Tiny projections on luminal membrane of each intestinal cell. Give the apical region striated appearance called brush border
microvilli
primary site for the removal of water and electrolytes and the storage of feces
transverse colon
Tubular glands located in the mucosa of the large intestine that are responsible for mucus secretion
crypts
What blocks the passage of feces and maintains continence?
contraction of internal anal sphincter and puborectalis muscle
