Corpus: Penis

The penis, together with the scrotum, forms the external male genital organs.

2.1. Classification

The penis can be subdivided anatomically into 3 sections:

• Root of the penis (radix penis)
• Body of the penis (corpus penis)
• Glans of the penis (glans penis)

2.1.1. Root of the penis

The root of the penis is the proximal portion, attaching the penis to the bony pelvis. This attachment is supported by ligaments and pelvic floor muscles, particularly the bulbospongiosus and ischiocavernosus muscles. These muscles help maintain an erection by compressing veins to restrict venous outflow and assist with ejaculation through rhythmic contractions. Two notable ligaments are:

• The fundiform ligament of the penis, which arises from the linea alba (a connective tissue structure in the abdominal wall) and continues into the body of the penis.
• The suspensory ligament of the penis, which originates from the lower edge of the pubic symphysis and pubic branches, attaching to the back of the penis.

At the base of the penis, the two diverging crura of the penis and the bulb of the penis (an enlargement of the spongy tissue surrounding the urethra) are located.

2.1.2. Body of the penis

The body of the penis makes up the majority of the organ's length. In cross-section, the body consists of three cylindrical structures of erectile tissue:

• Two corpora cavernosa (on the dorsal side)
• One corpus spongiosum (ventral side), which surrounds the urethra.

The two corpora cavernosa are separated by a thin connective tissue layer, called the septum penis. On the ventral side of the penis, a midline fusion called the penile raphe is visible.

2.1.3. Glans of the penis

The glans forms the distal portion of the penis, marking the transition from the body of the penis. This transition is outlined by a groove called the coronal sulcus. The glans contains a continuation of the spongy erectile tissue (corpus spongiosum glandis), giving it its characteristic rounded shape. The external opening of the urethra is located at the tip of the glans.

The skin covering the body of the penis is thin and highly mobile, forming a fold (the foreskin, or prepuce) that can retract to expose the glans. A small band of tissue, the frenulum, connects the underside of the glans to the prepuce, preventing the foreskin from retracting too far. Sebaceous glands located near the frenulum secrete lubricating substances.

2.2. Dimensions

On average, the penis measures 7 to 10 cm in length when flaccid and 12 to 18 cm when erect. To measure the erect length, a ruler is placed along the dorsal side of the penis, extending from its base to the tip of the glans. Circumference also varies significantly, ranging from 9 to 13 cm.

2.3. Arterial supply

The arterial blood supply to the penis is provided by branches of the internal pudendal artery, including:

• Artery of the bulb of the urethra
• Urethral artery
• Dorsal artery of the penis
• Deep artery of the penis

2.4. Venous drainage

Venous blood is drained via a deep and superficial system:

• The deep dorsal vein of the penis drains into the vesical venous plexus, prostatic venous plexus, or the internal pudendal vein.
• The superficial dorsal veins lie between the subcutaneous tissue and the deep fascia of the penis, draining blood from the penile skin into the external pudendal veins or directly into the femoral vein.

2.5. Innervation

Sensory innervation is provided by the dorsal nerve of the penis, which is a branch of the pudendal nerve.

Autonomic innervation is supplied by fibers from the lumbar sympathetic system (L1–L3) and the sacral parasympathetic system (pelvic splanchnic nerves). These fibers pass through the inferior hypogastric plexus.

The penis functions as both a reproductive and excretory organ. It facilitates the delivery of sperm into the female reproductive tract. Its anatomical structure allows sperm cells in semen to bypass the acidic vaginal environment, enabling them to reach the cervix. An erection, enabled by the erectile tissues (corpora cavernosa and corpus spongiosum), is necessary for penetration during intercourse.

Additionally, the penis serves as the conduit for urine excretion.

Diseases of the penis fall under the field of urology. Common conditions include:

• Erectile dysfunction
• Phimosis
• Balanitis
• Priapism
• Penile curvature
• Penile carcinoma

The penis is also frequently affected by sexually transmitted infections, such as:

• Syphilis
• Gonorrhoea
• Genital warts