SUPERFICIAL FASCIAL
LAYERS
The subcutaneous scrotal and perineal fasciae
originate from the superficial fascia of the abdominal wall known as Scarpa
fascia. This fascial layer is found deep to Camper fascia that backs
the skin as a loose layer of fatty tissue. The abdominal Scarpa fascia is a
true fascial layer that consists mainly of yellowy, elastic fibers that form a
continuous membrane across the lower abdomen. In the upper abdomen, this fascia
cannot be identified as a distinct membranous structure because it blends with
the general superficial fascia of the upper abdomen. In the lower lateral
abdominal region, Scarpa fascia is attached to the Poupart ligament, or
to the fascia lata of the upper thigh just below this ligament. It
passes over the external inguinal ring to continue inferiorly over the penis
and scrotum into the perineum, where it fuses with the posterior inferior
margin of the urogenital diaphragm. In the perineum, this fascia
attaches laterally to the inferior rami of the pubis and the superior rami of
the ischium and is called Colles fascia. As the fascia envelops the base
of the penis, it is joined by additional fibers that extend from the dorsal
penis to the symphysis, thus forming the fundiform ligament. Within the
scrotum, this fascia is termed dartos fascia (dartos flayed), as it is
reinforced by smooth muscle fibers.
Thus,
deep to the skin exists a continuous superficial fascial plane that begins in
the lower abdomen and extends inferiorly to encompass the penis, scrotum, and
anterior half of the perineum. Beneath it a potential space is formed in which
fluids or exudates can accumulate and spread along well-defined planes. The
points of fascial fixation, as described, lead to exudative, infectious, or
extravasative processes taking on a characteristic “butterfly” shape of
discoloration in this region. Although they can freely extend up the anterior
abdominal wall to the clavicles, such processes do not normally extend beyond
the inferior landmarks without penetrating this fascia.
In the
scrotal midline, an inversion of the dartos fascia forms the scrotal septum,
dividing the scrotal cavity into two halves. Anatomists differ as to whether a
further inward extension of Colles fascia, termed the major leaf of
Colles fascia, exists. It crosses the top of the scrotal cavity, thus forming a
roof and separating it from
the superficial urogenital pouch superiorly. Urine extravasation from the bulbar
urethra would not normally gain access to the scrotal cavity without
rupture or penetration of this major leaf of fascia. However, this fascia may
contain rows of transverse slitlike openings in some individuals, which would
allow urine access to the scrotal cavity.
As the
major leaf of Colles fascia nears the upper scrotal cavity, it divides near the
anterior margin of the scrotum,
with a portion extending inward (see Plate 2-3). This so-called deep layer
passes posteriorly, deep to the bulbospongiosus muscles, whereas the
major leaf of Colles fascia in the perineal region is entirely superficial to
the bulbospongiosus and ischiocavernosus muscles. The deep leaf of
Colles fascia lying beneath the bulbospongiosus muscle, together with the
superficial or major layer of fascia, forms a compartment for the bulbospongiosus
muscle.
