Wednesday, June 12, 2024
HomeAnatomyPenis Anatomy

Penis Anatomy

Gross Anatomy

The penile shaft is composed of 3 erectile columns, the 2 corpora cavernosa and the corpus spongiosum, as well as the columns’ enveloping fascial layers, nerves, lymphatics, and blood vessels, all covered by skin (see the following images). The 2 suspensory ligaments, composed of primarily elastic fibers, support the penis at its base.

Male reproductive organs, sagittal section.

Male reproductive organs, sagittal section.

View Media Gallery

Male reproductive organs, cross-section.

Male reproductive organs, cross-section.

View Media Gallery

The paired corpora cavernosa contain erectile tissue and are each surrounded by the tunica albuginea, a dense fibrous sheath of connective tissue with relatively few elastic fibers. The corpora cavernosa communicate freely through an incomplete midline septum. Proximally, at the base of the penis, the septum is more complete; ultimately, the corpora diverge, forming the crura, which attach to the ischiopubic rami.

The tunica albuginea consists of 2 layers, the outer longitudinal and the inner circular (see the image below). The tunica albuginea becomes thicker ventrally where it forms a groove to accommodate the corpus spongiosum. The tunica albuginea of the corpus spongiosum is considerably thinner (< 0.5 mm) than that of the corpora cavernosa (approximately 2 mm). Along the inner aspect of the tunica albuginea, flattened columns or sinusoidal trabeculae composed of fibrous tissue and smooth muscle surround the endothelial-lined sinusoids (cavernous spaces). In addition, a row of structural trabeculae arises near the junction of the 3 corporal bodies and inserts in the walls of the corpora about the midplane of the circumference.

Structure of the tunica albuginea.

Structure of the tunica albuginea.

View Media Gallery

The erectile tissue within the corpora contains arteries, nerves, muscle fibers, and venous sinuses lined with flat endothelial cells, and it fills the space of the corpora cavernosa. The cut surface of the corpora cavernosa looks like a sponge. There is a thin layer of areolar tissue that separates this tissue from the tunica albuginea.

Blood flow to the corpora cavernosa is via the paired deep arteries of the penis (cavernosal arteries), which run near the center of each corpora cavernosa (see the following image).

Arterial supply of the penis.

Arterial supply of the penis.

View Media Gallery

The single corpus spongiosum lies in the ventral groove between the 2 corpora cavernosa. The urethra passes through the corpus spongiosum. The corpus spongiosum possesses a much thinner and more elastic tunica albuginea to allow for distention of the corpus spongiosum for passage of the ejaculate through the urethra. The thinner tunica albuginea of the corpus spongiosum also allows the corpus to become less rigid during erection. Hence, the distal extension of the spongiosum, the glans penis, covers the tips of the corpora cavernosa to provide a cushioning effect. The urethral meatus is positioned just slightly on the ventral surface of the glans and is slitlike. The edge of the glans overhangs the shaft of the penis, forming a rim called the corona.

The 3 erectile bodies are surrounded by deep penile (Buck) fascia, the dartos fascia, and the penile skin. The deep penile (Buck) fascia is a strong, deep, fascial layer that is immediately superficial to the tunica albuginea. It is continuous with the deep fascia of the muscles covering the crura and bulb of the penis, the ischiocavernosus and bulbospongiosus.

On the dorsal aspect of the corpora cavernosa, the deep dorsal vein and paired dorsal arteries and branches of the dorsal nerves are contained within the deep penile (Buck) fascia. This fascia splits to surround the corpus spongiosum, and it extends into the perineum as the deep fascia of the ischiocavernosus and bulbospongiosus muscles. The deep penile (Buck) fascia encloses these muscles and each crus of the corpora cavernosa and the bulb of the corpus spongiosum, adhering these structures to the pubis, ischium, and the urogenital diaphragm.

Penile skin

The penile skin is continuous with that of the lower abdominal wall. Distally, the penile skin is confluent with the smooth, hairless skin covering the glans. At the corona, it is folded on itself to form the prepuce (foreskin), which overlies the glans. The subcutaneous connective tissue of the penis and scrotum has abundant smooth muscle and is called the dartos fascia, which continues into the perineum and fuses with the superficial perineal (Colle) fascia. In the penis, the dartos fascia is loosely attached to the skin and deep penile (Buck) fascia and contains the superficial arteries, veins, and nerves of the penis.

RELATED ARTICLES

Ovary Anatomy

Vaginal Anatomy

- Advertisment -

Most Popular