netter137

_*stric Secretion: III

GASTROINTESTINAL PHYSIOLOGY

Mucosal defense mechanisms

Mucosal Mechanisms

*“► Pepsin

Mucus    HCOj- * H- -► H₂0 + C0j

(neutrali/ation)

Gastric mucosa and submucosa protected trom Chemical injury by mucus-bicarbonate surface barrier    john a.crai^_*o

that neulralizcs gastric H* and by epilhelial 'tight junctions’ that prevenl H' access to subepilhelial tissue

Figurę 7.15 Mucosal Defense Mechanisms

The high-muein-conlaining mucus produced by the surface epithdial cells protects the stornach from abrasion and provides a relatively alkaline environment tor the epithelial cells. Tliis mucus layer traps

bicarbonate and remains relativelv stable, providing a pH ot 7.0 just abovc Ihe surface epithelium, compared to a pH ot 1.5 in the gastric lumen.

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