Abstract:
The penis is made up of three cylindrical erectile bodies.
The pendulous anterior portion hangs from the lower
anterior surface of the symphysis pubis. The two dorsolateral
corpora cavernosa are fused together, with an
incomplete septum dividing them. The third and smaller
corpus spongiosum lies in the ventral groove between
the corpora cavernosa, and is traversed by the centrally
placed urethra. Its distal end is expanded into a conical
glans, which is folded dorsally and proximally to cover the
ends of the corpora cavernosa and ends in a prominent
ridge, the corona. The corona passes laterally and then
curves distally to meet in a V ventrally and anterior to
the frenulum, a fold of skin just proximal to the external
urethral meatus.
The erectile tissue of the corpora cavernosa is made
up of blood spaces lined by endothelium enclosed in a
tough fibroelastic covering, the tunica albuginea. The
corpus spongiosum is smaller with a much thinner tunica
albuginea, and its erectile tissue surrounds the urethra.
Proximally, at the base of the pendulous penis, the
corpora cavernosa separate to become the crura, which
are attached to the inferomedial margins of the pubic
arch and adjoining inferior surface of the urogenital diaphragm.
The corpus spongiosum becomes expanded into
the bulb, which is adherent in the midline to the inferior
surface of the urogenital diaphragm. This is the fixed part
of the penis, and is known as the root of the penis. The
urethra runs in the dorsal part of the bulb and makes
an almost right-angled bend to pass superiorly through
the urogenital diaphragm to become the membranous
urethra.
