The Male Penis: Anatomy and Function
The penis is a male external genital organ that serves both urinary and reproductive functions. It can be divided into three main parts: the root, body, and glans.
Root
The root is the fixed part of the penis located in the superficial perineal pouch of the pelvic floor. It contains:
- Two crura
- Bulb of the penis
- Erectile tissues
- Ischiocavernosus and bulbospongiosus muscles
The bulbospongiosus muscles contract to empty the spongy urethra of residual urine or semen and during orgasm and ejaculation. The ischiocavernosus muscles surround the crura and contract to force blood distally from the cavernous spaces into the corpora cavernosa, adding rigidity to an erection.
Body
The body of the penis is suspended from the pubic symphysis and consists of three columns of erectile tissue:
- Two corpora cavernosa (along the sides)
- One corpus spongiosum (along the bottom)
The corpus spongiosum contains the urethra, which allows for the exit of urine or semen. It fills with blood to a lesser extent than the corpora cavernosa during an erection to prevent occlusion of the urethra, allowing semen to pass through during ejaculation.
Glans
The glans is the distal expansion of the corpus spongiosum and features the external urethral orifice.
Fascial Coverings
The penis has several layers of fascial coverings:
- Dartos fascia (superficial fascia of the penis)
- Buck's fascia (deep fascia of the penis)
- Tunica albuginea (surrounds each cavernous body)
Supporting Structures
Two ligaments support the root of the penis:
- Suspensory ligament
- Fundiform ligament
Foreskin
The foreskin (prepuce) is a double layer of skin and fascia found at the neck of the glans. It is connected to the glans surface via the frenulum.
Neurovascular Supply
Arterial Supply
- Dorsal arteries
- Deep arteries
- Bulbourethral artery
All branch from the internal pudendal artery, which arises from the anterior division of the internal iliac artery.
Venous Drainage
- Deep dorsal vein (drains cavernous spaces)
- Superficial dorsal veins (drain skin and cutaneous tissues)
Innervation
- Somatic innervation: Pudendal nerve (S2-S4)
- Parasympathetic innervation: Cavernous nerves from the pelvic plexus
The pudendal nerve continues as the dorsal nerve of the penis, supplying sensory and sympathetic innervation to the skin and glans. The cavernous nerves supply the corpus cavernosum and urethra, forming a network around the erectile tissue and causing vascular changes resulting in an erection.
