CPD ACCREDITED ARTICLE
A basic understanding of the normal neuroanatomy and
physiology of the lower urinary tract is required when in-
vestigating urinary incontinence in the horse. The lower
urinary tract of the horse consists of the bladder and blad-
der outlet (urethral sphincters and urethra). Bladder func-
tion is controlled by parasympathetic and sympathetic
neurons innervating the detrusor muscle. The bladder
outlet is controlled by parasympathetic and sympathetic
fibers innervating the internal urethral sphincter and so-
matic fibers innervating the external urethral sphincter.
The sympathetic nerve supply to the smooth muscle of
the detrusor and the internal urethral sphincter is supplied
by the hypogastric nerve, with the preganglionic fibers
originating from L1-L4 and synapsing in the caudal mes-
enteric ganglion. Postganglionic fibers supply both the
detrusor (α2-adrenoreceptors) and the internal urethral
sphincter (α-adrenorece