Small Intestines and Pancreatic Secretions Flashcards
What are the folds of Kerckring?
Longitudinal fold on the surface
What are villi?
Projections from folds, lines entire mucosal surface
What are microvilli?
Protrude from the surface of intestinal cells
Makes up the brush border
What are crypts?
Project down into the surface at the base of each villus
3 crypts/villus
What are enterocytes?
Columnar epithelial cell sin the villus
Function in digestion, absorption, and secretion
What are goblet cells?
Interspersed with enterocytes in villus
Secrete mucus
What are crypt cells?
Proliferative cells in the intestine for both enterocytes and goblet cells
Secretes fluid and electrolytes
Found in crypts at base of villus
What are the functions of small intestine motility?
Mix chyme with digestive juices and bile
Further reduce size of chyme particles
Bring chyme into contact with absorptive surface
Propel chyme
What are the three types of contractions?
Segmentation
Peristaltic
Migrating myoelectric complex
What is segmentation contractions?
Most common type of intestinal contractions
Circular smooth muscle of isolated segment contracts, propelling chyme in both directions
Effect is mixing chyme
Higher frequency in the proximal duodenum propels chyme towards colon
What are peristaltic contractions?
Serve to propel chyme down small intestine
Occur only over short distances
What are the migrating myoelectric complex of the small intestine?
Similar to stomach, occurs about every 90 minutes
Clears remaining chyme in small intestine
What is the peristaltic reflex/rush?
Contraction that moves intestinal contents along small intestine
Initiated by chyme in intestine that causes distension or mucosa irritation
Also caused by severe cases of infectious diarrhea
What is the intestinointestinal reflex?
Overdistension of one segment of intestine inhibits contractile activity in rest of intestine
Prevents movement of material into already severely distended section of bowel
What is the gastrocolic reflex?
Urge to defecate shortly after starting meal
Presence of food in stomach triggers increased colonic motility
Eventually leads to evacuation of colon to make way for remains of next meal
What is ileus?
Loss of or reduction in contractile activity of intestines in absence of obstruction
Results from irritation of the peritoneum
Caused by surgery, acute or systemic illness, electrolyte imbalance
What are acinar cells?
Pancreatic cells that produce peptidases, lipases, and amylases
What are centroacinar and duct cells?
Secrete pancreatic juice that contain high concentrations of HCO3
Brings duodenal contents within pH range necessary for optimal enzymatic digestion of nutrients
Describe the aqueous component of pancreatic secretion
Isotonic with plasma at all secretion rates
High rate - primarily Na and HCO3
Low rate - primarily Na and Cl
Describe the enzymatic component of pancreatic secretion
Lipase and amylase secreted ina ctive forms
Proteases secretes as inactive precursors
Trypsin inhibitor secrete to protect pancreas from autodigestion
How are the cephalic and gastric phases of pancreatic secretion regulated?
ACh acts on acinar and ductile cells
Distention of stomach initiates Vagovagal reflex
CCK-releasing peptide and monitor peptide act on I cells
How is the intestinal phase regulated?
Stimulated by acid and fat/protein digestion products in duodenum
Acid releases secretin from S cells in the duodenum, acts on ductule cells to increase HCO3 secretion
What is the role of CCK in pancreatic secretion?
Released from I cells in duodenum in response to fat/protein digestion products and CCK-RP and monitor peptide
Acts on acinar cells to increase enzyme secretion
What is the role of the vagovagal reflex in pancreatic secretion?
Initiated by acid and fat/protein digestion products
Stimulates enzyme secretion
How do CCK and ACh affect ductal cell secretion?
Potentiate action of secretin
Small amounts in the presence of CCK/ACh produce large amounts of pancreatic HCO3
Describe acute pancreatitis
Severe abdominal pain, tenderness, nausea/vomiting, diarrhea fever
Activated enzymes digest pancreatic tissue
Elevated serum amylase and lipase levels
Describe chronic pancreatitis
Due mostly to repeated episodes of acute pancreatitis
Similar symptoms to acute
Reduced secretion of water and bicarb leads to high protein concentration in pancreatic juice
What is cystic fibrosis?
Defect in Cl- channels
Reduces secretion of both aqueous and enzymatic components
Leads to malabsorption and steatorrhea
