Slide 9 -
Visceral pain-Mechanism The principal mechanical signal to which visceral nociceptors are sensitive is stretch; cutting, tearing, or crushing of viscera does not result in pain.
Visceral stretch receptors are located in the muscular layers of the hollow viscera, between the muscularis mucosa and submucosa, in the serosa of solid organs, and in the mesentery (especially adjacent to large vessels).
Mechanoreceptor stimulation can result from -rapid distention of a hollow viscus (e.g., intestinal obstruction), -forceful muscular contractions (e.g., biliary or renal “colic”), and -rapid stretching of solid organ serosa or capsule (e.g., hepatic congestion). -Similarly, torsion of the mesentery (e.g., cecal volvulus) or tension from traction on the mesentery or mesenteric vessels (e.g., retroperitoneal or pancreatic tumor) results in stimulation of mesenteric stretch receptors.
Chemical nociceptors -are contained mainly within the mucosa and submucosa of the hollow viscera. -activated directly by substances released in response to local mechanical injury, inflammation, tissue ischemia and necrosis, and noxious thermal or radiation injury. Such substances include H+ and K+ ions, histamine, serotonin, bradykinin and other vasoactive amines, substance P, calcitonin gene-related peptide, prostaglandins, and leuko-trienes.