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pl. penises, penes [L. penis, tail, penis, lust]
The male organ of copulation and, in mammals, of urination. It is a cylindrical pendulous organ suspended from the front and sides of the pubic arch. It is homologous to the clitoris in the female.
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PENIS AND OTHER MALE ORGANS ; SEE: circumcision; SEE: penile prosthesis; SEE: Peyronie's disease; SEE: priapism

The penis is composed mainly of erectile tissue arranged in three columns, the whole being covered with skin. The two lateral columns are the corpora cavernosa penis; the third (median) column (the corpus spongiosum) contains the urethra. The body is attached to the descending portion of the pubic bone by the crura of the penis. The conical head of the penis (the glans penis) contains the urethral orifice. The penis is covered with a movable hood (the foreskin or prepuce), under which is secreted the substance called smegma.

Hyperemia of the genitals fills the corpora cavernosa with blood as the result of sexual excitement or stimulation, thus causing an erection. The hyperemia subsides following orgasm and ejaculation of the seminal fluid. The organ then returns to its flaccid condition. The size of the flaccid penis does not correlate with that of the erect penis.

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