Chapter 64: Secretion of GI Tract (Discussion 8) Flashcards
Two Basic Types of Secretions
Digestive enzymes: local response to amount and type of food present
Mucus: lubricate and protect walls of tract
Salivary Glands
Parotid (mostly secretes amylyse)
Submandibular
Sublingual
Salivary Secretions
Amylases: digests starches
Mucus
Salivary Oral Hygiene Function
Anti-bacterial/removes bacteria
Esophagus Secretion
Mucus Secretion only
Mucus in Stomach
Alkaline
Protects wall from acid/secretions
Two major gland types in stomach
Oxyntic and pylori glands
Oxyntic Glands
Peptic Cells: pepsinogen (secretion stimulated by increase in acid in stomach) –> pesin: proteolytic enzyme activated in low pH (HCl)
Parietal Cells: HCl (secretion stimulated by Gastrin) and Intrinsic Factor (IF) - see pernicious anemia
Pylori Glands
Gastrin: secretion stimulated by gastric protein digestion
Pancreatic Secretions
HCO3-: neutralized acidic chyme, favorably stimulated by secretin
Digestive enzymes: secretion specific to what food products are present in the duodenum
Protein chyme (CCK), carbohydrate chyme, fat chyme (CCK)
Protein Chyme (CCK)
Trypsin and Chymotrypsin: Protein –> smaller chains
Carboxypeptidase: Protein –> individual amino acids
Carbohydrate Chyme
Pancreatic amylase: carbohydrates –> di/trisaccharides
Fat Chyme (CCK)
Pancreatic lipase: fat –> fatty acids/monoglycerides
Cholesterolesterase: breaks down cholesterol esters
Phospholipase: phospholipids –> fatty acids
Pancreatic Proteases Activation
- Secreted as inactive trypsinogen, chymotrypsinogen, & procarboxylpeptidate
- Secreted fluid also contains trypsin inhibitor
- Prevents digestion of pancreas by enzymes
- Enterokinase: Trypsinogen –> trypsin (in the intestine)
- Trypsin then activates others/ itself
- Pancreatic duct blockage/damage –> internal activation –> digestion of pancreas
Bile Function
- Fat digestion/absorption
- Bile acids emulsify fat particles –> smaller particles
- Help absorb end products across intestinal membrane
- Waste excretion
- Bilirubin
- Cholesterol
Bile constituents
Bile acids, cholesterol, organic compounds (CCK)
H2O and HCO3- (Secretin)
Gallbladder (still Bile)
- Bile stored in gallbladder if not secreted into duodenum immediately
- Removes H2O/electrolytes –> concentrates bile
- Ca+
- CCK stimulates emptying of gallbladder
- Gallstones: Precipitation of cholesterol in gall bladder
Small Intestine Secretions
No digestive secretions, digestive enzymes located within epithelial cells
Brunner’s glands and Crypts of Liberkuhn
Brunner’s glands (small intestine)
mucus-producing glands at beginning of duodenum
Highly alkaline (w/ lots of HCO3-) to neutralize gastric chyme
Failure –> peptic ulcers in duodenal wall
Crypts of Liberkuhn
Goblet cells: mucus
Enterocytes: secrete H2O and electrolytes (essentially ECF)
- Fluid flow carries digested products into villi cells on epithelium (provides transporting force of digestion products to be absorbed)
Large Intestine Secretion
Just mucus
Irritation (physical or nervous) –> lots of mucus and peristalsis –> diarrhea
