Figure 4 - Diffusion of refluxed gastric acid (H⁺) into the intercellular space.

The presence of abnormal tissue resistance, demonstrated by defects within the intercellular junctional complex between cells of the surface layers of esophageal (stratified squamous) epithelium, is shown to enable the ready diffusion of refluxed gastric acid (H⁺) into the intercellular space. Within this space, it encounters and activates chemosensitive nociceptors whose signals are transmitted via the spinal cord to the brain for symptom (heartburn) perception. Activation of the same nociceptors is also capable of initiating a short reflex arc to esophageal (longitudinal) smooth muscle as means of precipitating a sustained esophageal contraction. (Source: Barlow and Orlando,³⁵ with permission from American Gastroenterological Association.)