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A human penis

The penis is a male body part found on the outside of the body. It is used for urination and for sexual reproduction. The main sexual function of the penis is to be inserted into a woman's vagina and deliver semen to cause pregnancy. This activity is called sexual intercourse.

Structure[change | change source]

Uncircumcised penis with retracted foreskin and exposed glans

The human penis is made up of three types of tissue. It has two corpora cavernosa (special pieces of muscle) next to each other and a corpus spongiosum (spongy muscle) between them.

The end of the corpus spongiosum forms the glans penis underneath the foreskin (in uncircumcised men), or exposed (in circumcised men). The area on the bottom of the penis, where the foreskin is attached, is known as the frenulum.

The urethra, the tube where urine and semen travel through, runs down the corpus spongiosum (spongy tissue), and opens at the tip of the penis. Sperm are made in the testes (ball-like organs) and stored in the epididymis (layer of tissue) around the testes. During ejaculation, sperm are pushed up the vas deferens. Fluids are added by the seminal vesicles, the prostate gland and the bulbourethral glands to make semen.

Erection[change | change source]

A penis can become erect if a man is sexually aroused (or sometimes during sleep, even though there is no sexual stimulation). In an erection, the penis fills with blood. The blood makes the penis become longer, thicker and harder. Veins taking blood away from the penis get smaller, so less blood is taken through. Arteries bringing blood to the penis get wider, bringing more blood to the penis.

Ejaculation[change | change source]

Ejaculation is when semen is pushed from the penis. It usually happens during an orgasm. Men can ejaculate during sexual intercourse or by masturbation.

When a man has sexual intercourse with a woman, he places his erect penis within her vagina and moves it in and out. The vagina is warm and soft, and it places pressure on the man's penis. This makes the man have an orgasm and ejaculate. During orgasm, muscles push semen from the penis and into the vagina. Semen moves through the urethra and comes out of the hole at the tip of the penis.

In masturbation, a man can excite his own penis and other sensitive areas of his body, such as the scrotum, by rubbing the genital area. Ejaculation may also happen during sleep (called a 'wet dream'). A man must have started puberty before he can ejaculate.

Penis size in humans[change | change source]

The length and thickness of the penis is different for different men. The size of a soft penis (not erect) is much smaller than when it is erect. Some penises grow more when they get hard than other penises. In most cases, whether a penis is big or small, it can still be used for sex. It averages out to be around 3 to 6 inches long when not erect. The average size of an erect human penis is between 13 – 16 cm (5.1– 6 in).[1][2][3] The average circumference of a penis is 12.3 cm (4.85 in) when fully erect.

Circumcision[change | change source]

The foreskin is a fold of skin that covers the end of the penis. Cutting off the foreskin is called circumcision. The foreskin is connected to the head of the penis. During circumcision, the foreskin is removed from the penis. Circumcision is usually performed on infant males for religious or cultural reasons.

Some men have the foreskin cut off when they are adults because they have problems with their foreskin. Some men have the foreskin cut off because they want to change how their penis looks.

In some religions, babies and young boys have their foreskin cut off. This is expected in Islam and Judaism.[4][5] It is not required according to Christianity, but it is allowed and is quite common among some Christians. In Judaism, baby boys are required to have their foreskin removed as a sign of the covenant made with God.

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