Definition of Penis and Function

Penis is the male organ for urination and sexual intercourse.

The penis is an elongated, cylindrical structure made of connective and erectile tissue that extends outside the body from the base of the pelvis. Ligaments attach the root of the penis (segment within the body) to the pubic bone at the front of the pelvis and the ischial bones at the back of the pelvis.

The shaft is the length of the penis that extends outward from the body, and the glans is the end or head of the penis. The urethra exits the glans through an opening called the urethral meatus. A loose fold of skin, the foreskin (also called the prepuce), covers the glans at birth; beginning around 8 years of age the foreskin retracts from the glans when the penis is erect and returns to drape the glans when the penis is flaccid. Circumcision is a surgical operation to remove the foreskin.

The interior penis contains three channels: the corpus spongiosum runs along the underside of the penis and houses the urethra; the two corpora cavernosa run side-by-side along the top of the penis and engorge with blood to stiffen and enlarge the penis during erection.

A wall of fibrous tissue, the septum, separates and supports the corpora cavernosa. The inside of each corpus cavernosum is a honeycombed network of spaces (called trabeculae) that fill with blood when the penis is erect.

The erect penis is capable of penetrating the woman’s vagina during sexual intercourse, with sexual stimulation culminating in orgasm and ejaculation.

BalanitisCancer of the penis
Erectile dysfunctionGenital herpes
Human papillomavirus (hpv)Hypospadias
HypogonadismKlinefelter’s syndrome
ParaphimosisPeyronie’s disease

For further discussion of the penis within the context of the structures and functions of reproduction and sexuality, please see the overview section “The Reproductive System.”


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