The penis is the external reproductive organ in males and is the male organ for sexual intercourse, which helps in reproduction. It is composed of three cylindrical masses of cavernous tissue bound together by fibrous tissue and covered with Skin. The two masses are known as the corpus cavernous the third known as the corpus spongiosum. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped end of the penis. The glans, which also is called the head of the penis, is covered with a loose layer of Skin called foreskin called as the prepuce, this Skin is sometimes removed in a procedure called circumcision.

The opening of the Urethra, the tube that transports semen and urine, is at the tip of the glans penis. The penis also contains a number of sensitive nerve endings. The body of the penis is cylindrical in shape and consists of three internal chambers. These chambers are made up of special, sponge-like erectile tissue. This tissue contains thousands of large spaces that fill with blood when the man is sexually aroused. As the penis fills with blood, it becomes rigid and erect, which allows for penetration during sexual intercourse. The Skin of the penis is loose and elastic to accommodate changes in penis size during an erection.

The main function of the penis is erection, which occurs when numerous sexual stimuli are processed by the Brain and transmitted to the penis via the Nervous system. There is increased blood supply to the penis during erection. Semen, which contains sperm, is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm). When the penis is erect, the flow of urine is blocked from the Urethra, allowing only semen to be ejaculated at orgasm.

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