Fig. 1.

(A) Section of the sheep bladder wall. The section shows the urothelium, suburothelium and detrusor smooth muscle layers. The suburothelium is a complex structure of blood vessels, interstitial cells, afferent nerves and in this species a muscularis mucosae (m.m.). External physical and chemical agents can cause release of mediators (arrows) from the urothelium that could influence suburothelium structures to elicit nervous responses, changes to blood vessel tone and contractile responses of detrusor and possibly muscularis mucosae. Contractile responses could be mediated either by diffusion of mediators and/or by cell-to-cell communication. (B) A schematic drawing of the bladder wall, illustrating the cell types in different layers, as well as the stresses that may induce mediator release.