pept

1. 1

   System

   the whole body at work

   • In a healthy gut, the stomach maintains a delicate peace treaty between corrosive acid and delicate tissue.
   • The epithelium secretes a thick mucous gel layer and bicarbonate ions to create a pH-neutral microenvironment at the cell surface.
   • Prostaglandins act as the 'peacekeepers,' ensuring robust blood flow to repair minor nicks and inhibiting excess acid production.
   • This keeps the digestive fires contained within the lumen and away from the basement membrane.
2. 2

   Organ

   the healthy sequence, step by step

   • Parietal cells secrete HCl into the lumen for protein breakdown
   • Mucous cells create a physical barrier of viscous glycoproteins
   • Epithelial cells secrete bicarbonate to neutralize H+ ions at the surface
   • Prostaglandins (PGE2) maintain mucosal blood flow and cell turnover
   • The tight junctions prevent acid from leaking into the sub-epithelial space
3. 3

   Tissue & mechanism

   where and why it breaks

   • The core mechanism is the 'Barrier-Aggressor Mismatch' where the protective mucosal shield fails to neutralize gastric acid.
   • Once the barrier is breached, the H+ ions move from a high-concentration area (the lumen) to a low-concentration area (the tissue).
   • This 'acid back-leak' destroys the cells, triggers an inflammatory response that actually increases acid production, and eats through the tissue layer by layer.
   • Every intervention we have either turns down the fire or patches the hole.
4. 4

   Cell & molecule

   the break at its smallest scale

   • Inhibition of prostaglandin synthesis (NSAIDs) or mucosal damage (H. pylori)
   • Acid back-diffusion across the damaged epithelial lining
   • Activation of pepsin within the tissue causing structural proteolysis
   • Vascular erosion leading to hematemesis or melena
   • Transmural necrosis resulting in free air and peritonitis
5. 5

   The result

   what the break produces

   • Loss of the protective mucous/bicarbonate barrier
   • Retro-diffusion of hydrogen ions into the gastric mucosa
   • Pepsinogen is activated to pepsin within the tissue wall, causing autodigestion
   • Histamine release triggers further acid secretion and local vasodilation

• In a healthy gut, the stomach maintains a delicate peace treaty between corrosive acid and delicate tissue.
• The epithelium secretes a thick mucous gel layer and bicarbonate ions to create a pH-neutral microenvironment at the cell surface.
• Prostaglandins act as the 'peacekeepers,' ensuring robust blood flow to repair minor nicks and inhibiting excess acid production.
• This keeps the digestive fires contained within the lumen and away from the basement membrane.

• The core mechanism is the 'Barrier-Aggressor Mismatch' where the protective mucosal shield fails to neutralize gastric acid.
• Once the barrier is breached, the H+ ions move from a high-concentration area (the lumen) to a low-concentration area (the tissue).
• This 'acid back-leak' destroys the cells, triggers an inflammatory response that actually increases acid production, and eats through the tissue layer by layer.
• Every intervention we have either turns down the fire or patches the hole.

• PUD happens when the protective shield is either stripped away or the acid 'fire' becomes an inferno.
• Most often, H.
• pylori acts like a drill to penetrate the mucus, or NSAIDs shut down the prostaglandin 'peacekeepers' entirely.
• Once that shield has a hole, the same acid meant for your steak starts chewing through your own gastric wall.
• This triggers a cascade of local inflammation, tissue necrosis, and eventually, vascular erosion.

The chain that produces them

1. 1Retro-diffusion of hydrogen ions into the gastric mucosa
2. 2Pepsinogen is activated to pepsin within the tissue wall, causing autodigestion
3. 3Histamine release triggers further acid secretion and local vasodilation
4. 4Erosion reaches the submucosal vessels, leading to hemorrhage or perforation

• Labs help us quantify how much blood has been lost and identify the 'aggressor' behind the breach.

Uncertainty: The exact timing of transition from erosion to perforation is unpredictable and requires serial abdominal exams.