The penis is the male copulatory organ and the common conduit for expulsion of urine and sperm.

It is composed of cylindrical parts all somewhat densely held together.

The penis consists of a root, body and glans penis.

The root is attached to the pubic bone. The body is the pendulous part that is free in the flaccid state.

It is free of muscle except in its proximal part near the root.

Distally, the penis is composed of the glans penis which is the head of the penis. The glans penis is innervated and is thus sensitive.

Mechanism of erection

When a male is sexually stimulated, the smooth muscles in the penis relax and vessels dilate allowing blood to flow into the penis, hence it becomes turgid.

During emission semen is delivered into the urethra.

During ejaculation semen is expelled from the urethra.

After ejaculation, the penis gradually becomes flaccid following contraction of the smooth muscle and ejection of the blood from the penis.

Urine is expelled from the bladder through the urethra in the penis.

Blockage of the urethra results in retention of urine in the bladder, a very discomforting condition