Muscular structure at the male bladder outlet examined with successive celloidin-embedded slices.
OBJECTIVE
To re-examine the detailed anatomy of the muscular system at the bladder neck and proximal urethra in the male and to explore its function in urinary continence and micturition further.


METHODS
The pelvic organs, including bladder, prostate, and rectum, were obtained from 20 formalin-fixed adult male cadavers and were removed from the pelvic cavity and embedded in celloidin in their entirety. The embedded block was cut into successive slices with an immersing-alcohol microtome.


RESULTS
Circular muscle fibers of the detrusor at the bladder outlet consist of the anterior downward-projected circular muscle fibers of the bladder outlet (ADPC), the bilateral accumulated circular fibers, and the posterior circular fibers of the bladder outlet. Together, these fibers concentrically surround the internal urethral orifice and trigone muscle. The lower part of the ADPC surrounds the ventral surface of the proximal urethra. Longitudinal muscle fibers are radially inserted into the circular muscle around the internal urethral orifice. Numerous fibers from the ventral longitudinal muscle are inserted into the lower part of the ADPC. The upper part of the trigone muscle exists in bladder cavity; the lower part extends into the proximal urethra to surround the posterior and posterolateral surface of the urethra.


CONCLUSIONS
The ADPC and the upward extension of the rhabdosphincter comprise the anterior fibromuscular stroma. The circular muscle of the bladder outlet may be responsible for closure; the longitudinal muscle of the bladder outlet may be responsible for opening of the internal urethral orifice and proximal urethra.
Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital and Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China.
Xue-Mei
XM
Li
Department of Anatomy and Histology, Basic Medical College, Tianjin Medical University, Tianjin, China.
Hui
H
Yang
Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital and Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China.
Dai-Qing
DQ
Li
Department of Anatomy and Histology, Basic Medical College, Tianjin Medical University, Tianjin, China.
Ping
P
Zhang
Department of Urinary Surgery, First Center Hospital, Tianjin, China.
Qing-Tong
QT
Ma
Department of Anatomy and Histology, Basic Medical College, Tianjin Medical University, Tianjin, China. Electronic address: zhai.lidong@yahoo.com.
Li-Dong
LD
Zhai
D000368:Aged; D002102:Cadaver; D003101:Collodion; D006801:Humans; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000033:anatomy & histology*; D016610:Tissue Embedding; D014521:Urethra / Q000033:anatomy & histology*; D001743:Urinary Bladder / Q000033:anatomy & histology*
D003101:Collodion