THE STRIATED URETHRAL SPHINCTER - MUSCLE-FIBER TYPES AND DISTRIBUTIONIN THE PROSTATIC CAPSULE

Objective To clarify the muscle fibre types in the striated urethral s phincter and the pattern of distribution of this muscle in the prostat ic capsule. Materials and methods Twenty-three prostate glands obtaine d at radical prostatectomy were studied using a whole-organ technique, Each gland was sectioned from prostatic apex to base, including the b ladder neck and seminal vesicles, The slides were then traced on paper after staining with haematoxylin and eosin and the distribution of st riated muscle mapped, Two prostates were studied after sectioning with a cryostat and staining with adenosine phosphatase at pH 4.2, 4.6 and 4.93 to distinguish between the subclassification of Type 2 fibres. O ther sections were stained for nicotinamide adenine dinucleotide phosp hate with nitroblue tetrazolium, to distinguish fast from slow twitch fibres. Results Striated muscle was present within the anterolateral a spect of the prostatic capsule, extending from the prostatic apex to t he bladder neck. Three different fibre types were present; fast-twitch fatigue-sensitive, fast-twitch fatigue-resistant and slow-twitch. Con clusion There are three distinct fibre types in the prostatic capsular striated muscle, representing displaced muscle fibres from the striat ed urethral sphincter. The composition of three types makes it eminent ly suitable to function as a sphincter muscle.