PCOL 838 Exam 2: GI Pathophysiology +
Disorders Questions with Correct Answers
7 Major Functions of the GI Tract
1. Motility
2. Secretion
3. Digestion
4. Absorption
5. Metabolism
6. Excretion
7. Defense
Motility
Movement of intraluminal contents via coordinated contractions of smooth muscle. Includes
tonic contractions (sphincters) and phasic activity (segments between sphincters).
Secretion
Release of ions, water, enzymes, and bile
Maintains "mass balance" between input and output, aids digestion, and protects mucosa.
Digestion
Mechanical (chewing, peristalsis) + chemical breakdown (enzymes) of macromolecules into
absorbable units
Proteins → amino acids, fats → fatty acids, polysaccharides → monosaccharides.
Absorption
,Uptake of digested nutrients, water, electrolytes, and xenobiotics across mucosa into
blood/lymph.
Small intestine = main nutrient site
Colon = water/electrolytes.
Metabolism
Intracellular biotransformation of nutrients and xenobiotics (drug metabolism).
Excretion
Elimination of waste products via feces, bile, or urine.
Defense
Protection from acid, toxins, bacteria, and viruses
Mucus, bicarbonate, and immune factors all contribute.
4 Main Layers of the GI Tract
(lumen -> outward)
1. Mucosa
2. Submucosa
3. Muscularis Externa
4. Serosa
Mucosa
Epithelium: absorption and secretion
Lamina propria: connective tissue with blood/lymph vessels
Muscularis mucosae: thin smooth muscle aiding mucosal movement
, Submucosa
Loose connective tissue; supports mucosa; contains blood vessels and the submucosal
(Meissner’s) plexus.
Muscularis Externa
Circular + longitudinal muscle layers; responsible for motility; contains myenteric
(Auerbach’s) plexus.
Serosa
Outer connective tissue + mesothelium; provides protection and structural support.
Daily GI Fluid Balance
Total fluid entering the GI lumen each day (saliva, gastric, biliary, pancreatic, intestinal
secretions) ≈ 8–9 liters.
Most is reabsorbed, with only ~100–200 mL lost in feces.
“Mass balance” ensures water/electrolyte equilibrium — essential to avoid dehydration or
overload.
5 Main Routes of Absorption Across the Mucosal Membrane
1. Diffusion
2. Facilitated Diffusion
3. Active Transport
4. Pinocytosis
5. Filtration
Diffusion
passive movement down concentration gradient
Disorders Questions with Correct Answers
7 Major Functions of the GI Tract
1. Motility
2. Secretion
3. Digestion
4. Absorption
5. Metabolism
6. Excretion
7. Defense
Motility
Movement of intraluminal contents via coordinated contractions of smooth muscle. Includes
tonic contractions (sphincters) and phasic activity (segments between sphincters).
Secretion
Release of ions, water, enzymes, and bile
Maintains "mass balance" between input and output, aids digestion, and protects mucosa.
Digestion
Mechanical (chewing, peristalsis) + chemical breakdown (enzymes) of macromolecules into
absorbable units
Proteins → amino acids, fats → fatty acids, polysaccharides → monosaccharides.
Absorption
,Uptake of digested nutrients, water, electrolytes, and xenobiotics across mucosa into
blood/lymph.
Small intestine = main nutrient site
Colon = water/electrolytes.
Metabolism
Intracellular biotransformation of nutrients and xenobiotics (drug metabolism).
Excretion
Elimination of waste products via feces, bile, or urine.
Defense
Protection from acid, toxins, bacteria, and viruses
Mucus, bicarbonate, and immune factors all contribute.
4 Main Layers of the GI Tract
(lumen -> outward)
1. Mucosa
2. Submucosa
3. Muscularis Externa
4. Serosa
Mucosa
Epithelium: absorption and secretion
Lamina propria: connective tissue with blood/lymph vessels
Muscularis mucosae: thin smooth muscle aiding mucosal movement
, Submucosa
Loose connective tissue; supports mucosa; contains blood vessels and the submucosal
(Meissner’s) plexus.
Muscularis Externa
Circular + longitudinal muscle layers; responsible for motility; contains myenteric
(Auerbach’s) plexus.
Serosa
Outer connective tissue + mesothelium; provides protection and structural support.
Daily GI Fluid Balance
Total fluid entering the GI lumen each day (saliva, gastric, biliary, pancreatic, intestinal
secretions) ≈ 8–9 liters.
Most is reabsorbed, with only ~100–200 mL lost in feces.
“Mass balance” ensures water/electrolyte equilibrium — essential to avoid dehydration or
overload.
5 Main Routes of Absorption Across the Mucosal Membrane
1. Diffusion
2. Facilitated Diffusion
3. Active Transport
4. Pinocytosis
5. Filtration
Diffusion
passive movement down concentration gradient
