Chapter 64: Secretion of GI Tract (Discussion 8)

Question 1

Two Basic Types of Secretions

Answer 1

Digestive enzymes: local response to amount and type of food present

Mucus: lubricate and protect walls of tract

Question 2

Salivary Glands

Answer 2

Parotid (mostly secretes amylyse)

Submandibular

Sublingual

Question 3

Salivary Secretions

Answer 3

Amylases: digests starches

Mucus

Question 4

Salivary Oral Hygiene Function

Answer 4

Anti-bacterial/removes bacteria

Question 5

Esophagus Secretion

Answer 5

Mucus Secretion only

Question 6

Mucus in Stomach

Answer 6

Alkaline

Protects wall from acid/secretions

Question 7

Two major gland types in stomach

Answer 7

Oxyntic and pylori glands

Question 8

Oxyntic Glands

Answer 8

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

Question 9

Pylori Glands

Answer 9

Gastrin: secretion stimulated by gastric protein digestion

Question 10

Pancreatic Secretions

Answer 10

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)

Question 11

Protein Chyme (CCK)

Answer 11

Trypsin and Chymotrypsin: Protein –> smaller chains

Carboxypeptidase: Protein –> individual amino acids

Question 12

Carbohydrate Chyme

Answer 12

Pancreatic amylase: carbohydrates –> di/trisaccharides

Question 13

Fat Chyme (CCK)

Answer 13

Pancreatic lipase: fat –> fatty acids/monoglycerides

Cholesterolesterase: breaks down cholesterol esters

Phospholipase: phospholipids –> fatty acids

Question 14

Pancreatic Proteases Activation

Answer 14

• 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

Question 15

Bile Function

Answer 15

1. Fat digestion/absorption
   
   • Bile acids emulsify fat particles –> smaller particles
   • Help absorb end products across intestinal membrane
2. Waste excretion
   
   • Bilirubin
   • Cholesterol

Question 16

Bile constituents

Answer 16

Bile acids, cholesterol, organic compounds (CCK)

H2O and HCO3- (Secretin)

Question 17

Gallbladder (still Bile)

Answer 17

• 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

Question 18

Small Intestine Secretions

Answer 18

No digestive secretions, digestive enzymes located within epithelial cells

Brunner’s glands and Crypts of Liberkuhn

Question 19

Brunner’s glands (small intestine)

Answer 19

mucus-producing glands at beginning of duodenum

Highly alkaline (w/ lots of HCO3-) to neutralize gastric chyme

Failure –> peptic ulcers in duodenal wall

Question 20

Crypts of Liberkuhn

Answer 20

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)

Question 21

Large Intestine Secretion

Answer 21

Just mucus

Irritation (physical or nervous) –> lots of mucus and peristalsis –> diarrhea