DEEP FASCIAL LAYERS
Beneath Colles fascia, within the urogenital
triangle, is a potential space termed the superficial perineal compartment.
Within this space, confined by the inferior fascia of the urogenital
diaphragm on its deep aspect, lie the bulbospongiosus,
ischiocavernosus, and superficial transverse perineal muscles. In
addition, the bulb of the corpus cavernosum urethrae and the crura of
the corpora cavernosa penis are found here. At the middle of the base of
this triangle is the perineal body, a point of fusion between the
muscles of the superficial perineal compartment and the adjacent anal
triangle posteriorly.
The deep
fascia (Buck) of the penis is a distinct structure lying beneath the superficial
dartos or Colles fascia. Buck fascia is tenacious, dense, and
whitish in appearance. It covers the penile corpora as a strong, fibrous,
tubelike envelope and is adherent to the underlying tunica albuginea of
the penis, which immediately covers the paired cavernous bodies (see Plate
2-2). Buck fascia is distinct from the tunica albuginea that covers the paired
corporal cavernosa and the spongiosal bodies, though no demonstrable space
exists between these adjacent fascial layers. Near the base of each crus, Buck
fascia becomes less distinct as it merges with the tunica albuginea. At this
point, it is continuous with the deep suspensory ligament of the penis,
which is attached to the symphysis pubis (see Plate 2-1).
Buck
fascia originates distally at the penile coronary sulcus and forms a transverse intercavernous
septum, which separates the penis into two compartments: the paired corpora
cavernosa dorsally and the single spon- giosal body ventrally (see Plate 2-2,
cross section). In the perineum, this fascia forms three compartments by
covering each crus. Buck fascia covers the paired penile dorsal arteries and
nerves and the deep dorsal vein (see Plate 2-2, cross section). In the
perineum, Buck fascia lies beneath the reflected deep layer of Colles fascia
that contains the bulbospongiosus and the ischiocavernosus muscles (see Plate
2-1).
Visualized
in cross-sectional drawing on this page, a portion of Colles fascia (crural
septum) spreads to cover the outer surfaces of the bulbospongiosus muscle
and each ischiocavernosus muscle with the crura within. The cut margins of the crural septa,
as they surround the ischiocavernosus muscles, are observed in the upper drawing. The deep
layer of Colles fascia, shown extending posteriorly under the distal aspect of
the bulbocavernosus muscle, is also illustrated. At this point, the deep layer
of Colles fascia also turns backward around each penile crus and around the corpus
spongiosum. This reflected layer blends with Buck fascia surrounding the crura.
Thus, in
the urogenital triangle, four fascial layers cover the bulbous spongiosum and
urethra. First is the perineal layer of Colles fascia external to the bulbospongiosus muscle.
Beneath this is the deep extension of Colles fascia below the
bulbospongiosus muscle, followed by Buck fascia and, finally, the tunica
albuginea. Only three fascial layers cover each crus of the penis: Colles
superficial fascia overlying the ischiocavernosus muscles and Buck fascia
beneath this muscle, which blends with the deep reflected layer of Colles fascia
over the tunica albuginea.