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The Intestinal Phase VS Colonic Phase - Coggle Diagram
The Intestinal Phase VS Colonic Phase
Intestinal Mucosa & Hydroelectrolyte (Amplification, Cell Types & Water Balance)
Surface Area Amplification
Circular Folds (Valves of Kerckring)
Villi
Microvilli (Enterocyte Brush Border)
Cell Types & Daily Hydroelectrolyte Balance
Secretory Diarrhea Pathophysiology (e.g., Cholera)
Elevated intracellular cAMP
Active apical Cl⁻ secretion via CFTR channels + Inhibition of electroneutral Na⁺ reabsorption
Massive osmotic water secretion into the intestinal lumen
Daily Water Balance Matrix (≈ 8,500 mL Total Intake/Secretion)
Outflow & Reabsorption
Total Absorbed: ~8,300 mL (Small & Large Intestine)
Fecal Loss: ~200 mL
Inflow Sources (~8,500 mL Total Input)
Intestinal Juice:1,000 mL
Pancreatic Juice: 1,500 mL
Biliary Output: 500 mL
Gastric Juice: 2,500 mL
Salivary Secretion: 1,500 mL
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Mucosal Epithelial Specialization
Goblet Cells
Crypt-located cells secreting protective lubricating mucus
Enteroendocrine Cells
Secretory units producing GI regulatory hormones (e.g., CCK, secretin, GIP)
Enterocytes
Primary absorptive cells
Apical brush border (digestive enzymes + solute transporters) + Basolateral Na⁺/K⁺-ATPase pumps
Intestinal & Colonic Transit (Segmentation, Peristalsis & Gas)
Intestinal Smooth Muscle Motility
Mixing Movements (Segmentation)
Localized circular muscle contractions
12–15 cycles/min; NO net forward movement
Mixes chyme with biliary & pancreatic juices
Peristaltic Movements (Propulsion)
Slow Waves (1–2 cm/min): Continuous progression (~5–6 h)
Rapid Waves (2–25 cm/min): Long-distance "intestinal rush"
Neural Coordination of Peristalsis (Myenteric Reflex)
Propulsive Segment (Behind Bolus)
Cholinergic interneurons activate excitatory motor neurons
Release Acetylcholine (ACh)
Smooth muscle contraction
Receiving Segment (Ahead of Bolus)
Inhibitory motor neurons release Vasoactive Intestinal Peptide (VIP) and Nitric Oxide (NO)
Smooth muscle relaxation and luminal distension
Defecation Mechanics (RAIR, RAER & Voluntary Control)
Refusal To Defecate
Voluntary contraction: External anal sphincter & puborectalis muscle
Urge subsides in 30–45 s via rectal adaptation
Accepted Defecation
Rectal distension
RAIR (Rectoanal Inhibitory Reflex)
Involuntary relaxation of the internal anal sphincter
Valsalva maneuver (Glottis closure, diaphragm & abdominal strain)
RAER (Rectoanal Excitatory Reflex)
Voluntary relaxation of the external anal sphincter
Fecal expulsion
Colonic Fluid & Gas
Origin: Swallowed air + bacterial fermentation/ putrefaction (Coliforms, Lactobacilli,
C. perfringens
)
Gas: 400–1,500 mL/day
Excretion: ~100 mL in feces
Input: ~1,500 mL/day