Development of Urodynamic Standards for Quality Control

1.1 Anatomy of the lower urinary tract Initially, a brief summary of the anatomy of the lower urinary tract will be presented. The bladder is a hollow muscular organ in pelvis lined by a mucous membrane and covered on its outer aspect partly by peritoneal serosa and partly by fascia (Lich et al. 1978; Dixon and Gosling 1987). The muscularis of the bladder is formed of smooth muscle cells which comprise the detrusor muscle. The detrusor muscle is often described as consisting of three layers, the muscle fibres of the outer and inner layers tending to be orientated longitudinally, while those of the middle layer are circularly disposed. Woodburne (1960) has clearly shown that the musculature of the bladder is a "muscular meshwork". The constituent muscle bundles frequently branch and reunite with one another to form this interlacing meshwork. The bladder is profusely supplied with autonomic nerve fibres which form a dense plexus among the smooth muscle cells (Dixon and Gosling 1987). In the male bladder neck, the smooth muscle cells form a complete circular collar which forms the internal urethral sphincter and extends distally to surround the preprostatic portion of the urethra. In the female bladder neck, muscle bundles extend obliquely or longitudinally into the urethral wall. There is the rich sympathetic innervation in the male bladder neck, while the female bladder neck is well supplied with the parasympathetic innervation (Gosling et al. 1977; Dixon and Gosling 1994). The male urethra is considered in four regional parts: preprostatic, prostatic, membranous and spongiose. In the membranous urethra, muscle coat consists of a relatively thin layer of smooth muscle bundles and a layer of circularly orientated striated muscle fibres forming the external urethral sphincter. In the female urethra, the muscle coat consists of an outer sleeve of striated muscle, which forms the external sphincter together with an inner coat of smooth muscle fibres (Dixon and Gosling 1994).