The =scrotum=, in which the testicles and the lower parts of the
spermatic cords are situated, is somewhat globular in form, but is
commonly asymmetrical, since one testicle—more often the left—is the
larger and more dependent. It varies in form and appearance in the same
subject, according to the condition of its subcutaneous muscular tissue.
The latter contracts on exposure to cold, so that the scrotum is drawn
up and becomes thicker and wrinkled; when relaxed under the influence of
heat or fatigue, or from debility, it becomes smooth and pendulous, with
a constriction or neck superiorly. It consists of layers which
correspond with those of the abdominal wall; considered from without
inward these are:
(1) The =skin=, which is thin, elastic, usually black in color, and
smooth and oily to the touch. It presents scattered short fine hairs,
and is abundantly supplied with very large sebaceous and sweat glands.
It is marked centrally by a longitudinal furrow, in which is a line, the
=raphé scroti=; this is continued forward on the prepuce and behind on
the perineum.
(2) The =dartos= (Tunica dartos) is reddish in color and is closely
adherent to the skin except superiorly. It consists of fibro-elastic
tissue and unstriped muscle. Along the raphé it forms a median
partition, the =septum scroti=, which divides the scrotum into two
pouches. Dorsally the septum divides into two layers which diverge on
either side of the penis to join the abdominal tunic. At the bottom of
the scrotum fibers connect the dartos closely with the tunica vaginalis
and the tail of the epididymis, constituting the =scrotal
ligament=.[143] Elsewhere the dartos is loosely connected with the
underlying tunic by areolar tissue which contains no fat.
(3) The scrotal =fascia=, which is apparently derived from the oblique
abdominal muscles.
It has been customary to describe three layers of fascia, in
conformity with the accounts given in text-books of human anatomy.
These are: (1) the intercolumnar or spermatic fascia, derived from the
margin of the external inguinal ring; (2) the cremasteric fascia,
derived from the internal oblique muscle; (3) the infundibuliform
fascia, derived from the fascia transversalis. The first two cannot be
distinguished by dissection and the third is (in the scrotum) fused
with the parietal peritoneum of the tunica vaginalis.
(4) =The parietal layer of the tunica vaginalis.=—This is a fibro-serous
sac which is continuous with the parietal peritoneum of the abdomen at
the internal inguinal ring. It is thin above, but is thick in its
scrotal part, where it is strengthened by fibrous tissue (Lamina
fibrosa) derived from the transversalis fascia. It will be described
further under the caption tunica vaginalis.[144]