7 - E-Lib FK UWKS

2
The Muscular Systems
of the Bladder Neck and Urethra
Jens-Uwe Stolzenburg ∙ Jochen Neuhaus ∙ Lars-Christian Horn ∙ Evangelos N. Liatsikos ∙
Thilo Schwalenberg
The external sphincter (urethral sphincter) ensures
continence after radical prostatectomy. The main
goal of the surgeon should be the protection of the
urethral sphincter, even though the internal sphincter
(vesical sphincter) and the pelvic floor muscles
also contribute to the continence mechanism. There
is controversy in the literature regarding the course
and structure of the urethral sphincter. Most important
for prostate surgery is the apex of the prostate, as
at this level striated muscle fibres of the external urethral
sphincter are already prominent at the ventral
aspect. Furthermore, at the apex of the prostate there
is the most intimate contact between the external
sphincter, the puboprostatic ligaments and the endopelvic
fascia. It is generally accepted that the urethral
sphincter is a distinct muscular structure and is not
part of the pelvic floor musculature (even though they
are adjacent structures). There is no muscular connection
to the levator ani muscle [1–3].
We have performed a study to clarify the structure
of the muscular systems of the lower urinary tract,
from the bulb of the penis up to the actual bladder
neck. Fifty autopsy preparations from males of all
ages, from newborn to 82 years, were examined. In
order to preserve their anatomical interrelationships,
all organs of the lower urinary tract (urinary bladder,
bladder neck, urethra) and surrounding organs (pros-
2.3
tate, seminal vesicles, symphysis, rectum, musculature
of the pelvic floor) were anatomically dissected
and fixed in buffered 4% formalin. In so doing, all tissue
around the urethra was preserved. The fixed organ
blocks were completely cut on a modified microtome
(Tetrander Jung) in serial sections at a thickness
of 10 µm. Serial sections were made in frontal (coronal),
sagittal and transverse (horizontal) planes and
were stained with resorcin–fuchsin, haematoxylin–
eosin, Crossmon trichrome staining, silver stain and
by smooth muscle cell α-actin immunohistochemistry.
All serial sections were systematically examined
at different magnifications [1]. Figure 2.3.1 shows histological
images from a transverse section series from
a newborn. It is evident that the external sphincter is
a separate musculature with a boundary layer of connective
tissue separating it from the surrounding pelvic
musculature. Histomorphological investigations
and magnetic resonance imaging in adults have confirmed
this morphological fact [4–6]. In many textbooks
a transversus perinei profundus muscle is described
as part of the "urogenital diaphragm". As is
shown in Fig. 2.3.1 and has been documented in our
published study [4], we were not able to confirm the
existence of this muscle structure. Thus we consider
the urethral sphincter to be an autonomous muscular
unit in all age groups.