Functional anatomy and neural regulation of the lower urinary tract in female dogs: A review

A review of the literature of the functional anatomy and neural regulation of the lower urinary tract is presented. The two main functions of the lowe r urinary tract are the storage and the periodic elimination of urine. The smooth muscle of the bladder exhibits intermittent contractions as the blad der adapts its capacity to increasing volumes and it exhibits sustained con tractions associated with relaxation of the external sphincter to effect mi cturition. During storage, tension receptors in the bladder wall initiate e xternal sphincter contraction (somatic), internal sphincter contraction (sy mpathetic), detrusor inhibition, and parasympathetic ganglion inhibition (s ympathetic). The storage phase can be switched to the micturition phase eit her voluntarily or involuntarily. Neuroanatomical and electrophysiological studies reveal that medial and lateral cell groups in the dorsolateral pens may be regarded as micturition and storage control centres, respectively.