Male External Genital Organs

Male internal genital organs | Main Anatomy Index | The lymphatic system

Last updated 30 March 2006

Male External Genital Organs

The Scrotum

• The scrotum develops from an out-pouching of the skin of the anterior abdominal wall.
• The scrotum is a loose cutaneous fibromuscular sac that is situated posteroinferior to the penis and inferior to the pubic symphysis.

• Its bilateral formation is indicated by the midline scrotal raphe.
• This continues on the ventral surface of the penis as the penile raphe and posteriorly along the median line of the perineum to the anus as the perineal raphe.

• The scrotum is composed of skin and dartos muscle.
• The dartos muscle is firmly attached to the skin and consists largely of smooth muscle fibres that contract under the influence of cold, exercise, and sexual stimulation.
• Under these conditions the wall of the scrotum becomes contracted and firm.
• Its skin becomes rugose.
• Contraction of the dartos and cremasteric muscles causes the testes to be drawn up against the body.

• In hot weather the scrotum relaxes and allows the testes to hang freely away from the body.
• This provides a larger skin surface for the dissipation of heat.
• These reflexes of the scrotum in response to temperature help to maintain a stable temperature, an important function because spermatogenesis is impaired by extremes of heat or cold.

• In older men the dartos muscle loses its tone and the scrotum tends to be smoother and to hang down further.

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Arterial Supply of the Scrotum

• The external pudendal arteries supply the anterior aspect of the scrotum.
• The internal pudendal arteries supply its posterior aspect.
• It also receives branches from the testicular and cremasteric arteries.

Venous Drainage of the Scrotum

• The scrotal veins accompany the arteries and join the external pudendal veins.

Innervation of the Scrotum

• Its anterior part is supplied by the ilioinguinal nerve.
• Its posterior part is supplied by the medial and lateral scrotal branches of the perineal nerve and the perineal branch of the posterior femoral cutaneous nerve.

Lymphatic Drainage of the Scrotum

• The lymph vessels from the scrotum drain into the superficial inguinal lymph nodes.

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The Penis

• This is the male organ of copulation.
• It is the common outlet for urine and semen.

• It is composed of 3 cylindrical bodies (L. corpora) of erectile cavernous tissue that are enclosed by a dense white fibrous capsule, the tunica albuginea.
• Superficial to this layer is the deep fascia of the penis, which forms a common covering for the two corpora cavernosa and the corpus spongiosum.

• The skin of the penis is very thin, dark in colour, and loose.

• Two of the three erectile bodies, the corpora cavernosa penis, are arranged side by side in the dorsal part of the penis.

• The corpus spongiosum penis lies ventrally and contains the spongy urethra.

• The corpora cavernosa are fused with each other in the median plane.
• Posteriorly they separate to form 2 crura (L. legs).
• The crura are attached on each side to the ischiopubic ramus.
• They support the corpus spongiosum penis, lying between and inferior to the ischiopubic ramus.

• The penis consists of a root and a body (shaft).
• The dorsal surface of the penis faces posteriorly when the penis is erect, and anteriorly when it is in the flaccid state.

• The dorsum the penis is continuous with the anterior abdominal wall.
• The other aspect is referred to as the ventral surface.

The Root of the Penis

• This is its attached portion (radix).
• It is located in the superficial perineal space between the perineal membrane superiorly the superficial perineal fascia inferiorly.

• The root consists of crura, bulb, and associated muscles (bulbospongiosus).

The Bulb of the Penis

• This is located between the crura the superficial perineal space.
• The enlarged posterior part of bulb is penetrated superiorly by the spongy urethra.

The Body of the Penis

• This is the free part, which is pendulous in the flaccid condition.
• Except for few fibres of the bulbospongiosus near the root, the body of the penis has no muscles.
• It consists of the corpora cavernosa and corpus spongiosum and is covered by skin.
• The spongy urethra is within the corpus spongiosum.

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The Glans Penis

• Distally, the corpus spongiosum penis expands to form the conical glans penis.
• This is the concavity of that covers the free blunt ends of the corpora cavernosa.

• The glans has a higher concentration of sensory nerve endings than the rest of the body of the penis.
• It is particularly sensitive to physical stimulation.

• The prominent margin of the glans penis is the corona (L. crown).
• This projects beyond the ends of the corpora cavernosa penis.

• It overhangs an obliquely grooved constriction called the neck of the penis.
• The slit-like opening of the spongy urethra is near the tip of the glans penis.
• It is called the external urethral orifice (meatus).

The Prepuce or Foreskin of the Penis

• This is where the skin and fasciae of the penis are prolonged as a free fold of skin (L. praeputium, foreskin).
• This covers the glans penis to a variable extent.

• The frenulum of the prepuce, which is a median fold, passes from the deep layer of the prepuce to a point just inferior to the external urethra orifice.

The Fundiform Ligament

• The weight of the body of the penis is supported by 2 ligaments that are continuous with the fasciae of the penis.
• The fundiform ligament arises from the membranous layer of subcutaneous tissue of the lower abdomen (Scarpa's fascia).

The Suspensory Ligament

• This is a condensation of deep fascia in the form of a thick, triangular, fibroelastic band.
• It arises from the anterior surface of the pubic symphysis and passes inferiorly.
• It splits to form a sling, which is attached to the deep fascia of the penis at the junction of its fixed and mobile parts.

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Arterial Supply of the Penis

• The arteries to the penis are:

1. The dorsal arteries, which run in the interval between the corpora cavernosa on each side of the deep dorsal vein;
2. The deep arteries, which pierce the crura and run within the corpora cavernosa;
3. And the artery to the bulb, which enters on each side.

• The dorsal and deep arteries are branches of the internal pudendal arteries.
• The deep arteries are the principal vessels that supply the cavernous spaces (erectile tissue) in the three corpora.

• They give off numerous branches that open directly into these spaces.
• When the penis is flaccid, these arterial branches are coiled; hence, they are called helicine arteries (G. helix, a coil).

Venous Drainage of the Penis

• Blood from the cavernous spaces is drained by a venous plexus that joins the deep dorsal vein located in the deep fascia.
• Blood from the superficial coverings of the penis drain into the superficial dorsal vein and then into the superficial external pudendal vein.

Lymphatic Drainage of the Penis

• From most of the penis, lymph drains into the superficial inguinal lymph nodes.
• Vessels from the glans penis drain into the deep inguinal lymph nodes.

Innervation of the Penis

• The dorsal nerve of the penis is one of the two terminal branches of the pudendal nerve.
• The dorsal nerve arises in the pudendal canal and passes anteriorly into the deep perineal space.
• It then runs to the dorsum of the penis where it passes lateral to the arteries.
• It supplies both the skin and glans penis.

• The penis is richly innervated with sensory nerve endings, especially the glans.
• The cavernous nerves from the inferior hypogastric plexus pass through the urogenital diaphragm to reach the penis.

• The skin covering the root of the penis is supplied by the ilioinguinal nerve and the posterior scrotal branches of the perineal nerve.

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