Normal Anatomy of the Penis
The penis is composed of three
cylinders enclosed in 2 thin layers of muscle/fascia and a layer of
skin. The tip carries the glans, a bell shaped mass of
erectile tissue that is very sensitive to touch as it is rich in
One of the three cylinders is the
corpus spongiosum that contains the urethra. The urethra is the
tube through which urine flows. It ends in the glans
with the urethral meatus (opening through which urine flows.
The corpus spongiosum courses along the length of the penis, on its
under surface, under the skin.
The two other cylinders are the
corpora cavernosa. These are the structures responsible for
rigidity and therefore erection. The course next to each other above
the corpus spongiosum under the skin of the upper surface of the
penis. Each corpus cavernosum is composed of erectile tissues
in the form of microscopic spherical spaces (Sinusoids) that
accommodate blood and expand when blood flow into them increases.
Each sinusoid is surrounded by microscopic muscles that
control its diameter. The sinusoids are enclosed in the outer wall
of the corpus cavernosum that is a firm, expandable layer of fibrous
tissue named the "tunica albuginea".
The neurovascular bundle is a
collection of nerves, arteries and a vein that course along the
penis on its upper surface, from the glans to the base of the penis.
It includes the nerves that convey sensation from the glans: the
dorsal nerve of the penis.
At the base of the penis (towards the
abdomen), the corpora cavernosa are attached to the bony pelvis by
adhesions to between their deepest parts (the crura) and
bone, and by a ligament that attaches the corpora cavernosa to the
middle of the pelvis and to the anterior abdominal wall: the
Each corpus cavernosum has a feeding
artery that fills it with blood, and a draining vein
that lets blood out. The vein starts inside the corpus cavernosum
between its wall (tunica albuginea) and the sinusoids, such that if
the sinusoids expand, they may compress the vein and prevent blood
from exiting the corpus cavernosum.
The penis is covered by skin,
underneath which is a thin layer of tissue named the Colle's
fascia, beneath which is a thin muscle called Dartos Muscle
or Buck's fascia
Normal length is variable from race
to race, but there is an accepted average. Measurement are taken in
the non-erect state by pulling on the glans forwards to stretch the
penis and dipping the ruler into the pubic fat that surrounds the
penis down to the bone, so that the measurement is taken from the
bone to the glans, and not from the skin to the glans. This measures
the actual length of the penis and not the apparent length. The
stretched non-erect length should at least be 7cm. In the erect
state, length measured in the same way should be at least 11 cm. The
length of the vagina is 10cm on average, which makes 11 cm a normal
length for the penis.
There is no consensus about the
normal diameter, but if measured with a taper, the perimeter should
at least be 10cm. It has to be noted that the vagina is surrounded
by muscles that tighten it around the penis, regardless its
The penis is mostly straight.
However, many men have variable degrees of curvature affecting the
penis. This poses cosmetic problems. This may also make intercourse
difficult or painful to the female if curvature is more than 30
degrees, especially it is downwards or to a side.
By curvature we mean that the penis
is straight at its base but has a bending point distally. A straight
penis pointing upwards, downwards or to a side without a bent is not
The penis usually makes an angle of
around 90 degrees relative to the surface
of the abdomen.
may vary. The angle may be acute with the penis pointing
upwards, or obtuse with the penis pointing downwards.
This is acceptable as long as it does not make intercourse difficult
or disturb the individual or his partner psychologically. A rigid
penis pointing downwards is an erect
penis. Erection does not necessarily mean that the
penis should point forwards or upwards.
This is the urine outlet at the tip of the penis in the glans.
Hypospadias is a disorder where the urethral meatus is not at the
tip but is somewhere along the lower surface of the penis. This may
require surgical correction.