Oelrich T M
Am J Anat. 1980 Jun;158(2):229-46. doi: 10.1002/aja.1001580211.
The male urethral sphincter is a striated muscle in contact with the urethra from the base of the bladder to the perineal membrane. The individual muscle fibers are 25 to 30% smaller than fibers of associated muscles and are embedded in connective tissue which obscures the visibility of the whole muscle. The muscle primordium is laid down around the urethra prior to the development of the prostate. Subsequently, the prostate develops as a diverticulum of the urethra and grows into the developing sphincter, thinning the overlying musculature. With the onset of puberty, accelerated growth of the prostate displaces the sphincter, with atrophy of the overlying muscle, resulting in what may appear to be isolated segments of the sphincter muscle distributed around the prostate. The prostate overgrows the anterior portion of the urethra and the associated sphincter muscle. There is no distinct superior fascia of the so-called urogenital diaphragm separating the sphincter muscle from the prostate. The fascia of the sphincter muscle is inseparable from the prostatic sheath, is oriented vertically, and passes through the urogenital hiatus to unite with the fascia of the pudendal canals at the isochiopubic rami. Thus, the sphincter muscle is a component of a bladder-urethra-prostate-sphincter unit which lies within the pelvis, in the urogenital hiatus, and rests upon the perineal membrane. The concept of a urogenital diaphragm is not borne out by this study.
男性尿道括约肌是一种横纹肌，从膀胱底部至会阴膜与尿道相接触。其单个肌纤维比相关肌肉的纤维小25%至30%，并嵌入结缔组织中，这使得整块肌肉难以看清。在前列腺发育之前，肌原基就围绕尿道形成。随后，前列腺作为尿道的憩室发育，并长入正在发育的括约肌，使覆盖其上的肌肉组织变薄。青春期开始时，前列腺加速生长，使括约肌移位，覆盖其上的肌肉萎缩，导致括约肌肌肉似乎以孤立的节段分布在前列腺周围。前列腺过度生长在尿道前部及相关的括约肌肌肉上。不存在将括约肌与前列腺分隔开的所谓尿生殖膈的明显上筋膜。括约肌的筋膜与前列腺鞘不可分离，呈垂直方向，穿过尿生殖裂孔，在耻骨坐骨支处与阴部管的筋膜相连。因此，括约肌是膀胱 - 尿道 - 前列腺 - 括约肌单元的一个组成部分，该单元位于盆腔内、尿生殖裂孔中，并依托于会阴膜。本研究并未证实尿生殖膈的概念。
