Human penis

A penis can become erect ("hard") if a male 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. It is normal for the penis to be erect when a male wakes up. This is commonly called morning wood. It is also normal for male teenagers and men to have an erection several times per night when sleeping. If this does not happen, the person may have a bad medical problem or depression (a mental health problem.) Not being able to have an erection can also be caused by various common drugs, including antidepressants and drugs taken to control high blood pressure.[1] During the day, an erection sometimes happens for no reason, or when undressing. This is most common in young teenagers and is normal. People call this a spontaneous (sudden or surprise) erection. A slang word for an erection is a boner.

Ejaculation is when semen is pushed from the penis. It usually happens during an orgasm. Males can ejaculate during sexual intercourse or by masturbation. There are usually 40 million or more sperm in the semen ejaculated.[2] Semen usually has a slight smell of chlorine and ammonia. It is not poisonous, but it is very bad if it gets in someone's eye. The enzymes semen contains to penetrate the egg in a female will also attack the eye. Be careful not to ejaculate into your eye or your partner's eye. Semen contains proteins and fructose (a kind of sugar.) Some people say it tastes sweeter if the man eats a lot of fruit. Scientists have not proven that. Smoking, or drinking coffee, tea or colas that contain caffeine can create a bitter flavor.[3] Semen is slimy when wet. Eventually, it dries in the air and hardens like glue.

In reproductive sexual intercourse between a male and female, the erect penis is inserted into the vagina and moved in and out. The vagina places pressure on the penis, which can cause the male to have an orgasm and ejaculate into the vagina, causing insemination (meaning that semen enters the female's reproductive system.) A man can put a condom on his penis to prevent semen from entering the female's reproductive system. A condom is very thin, so having sex still feels good. If used correctly, a condom usually stops the woman from getting pregnant and having a baby. A condom also lowers the chance of getting a sexually transmitted infection from the sexual partner or giving a sexually transmitted infection to the sexual partner. Vaccinating young people (both girls and boys) before the age when they first have sex can reduce their risk of getting one infection called HPV. The United States CDC says the HPV vaccine should be given at age 11 or 12 years but can be started at age 9.[4] HPV increases the risk of cancer, including cancer in the throat or neck if people have oral sex (licking, kissing or sucking on the penis.)[5] HPV can be under the foreskin if the penis has a foreskin, and in the semen whether the penis is circumcised or uncircumcised.

Orgasm and ejaculation can happen during many types of sex acts including anal and oral sex, and when masturbating. A condom should be used during anal sex to avoid getting a urinary tract infection. Masturbation can include touching and rubbing the penis and other sensitive areas of the body, such as the scrotum, and other places in the genital area. This can be done naked or through clothes. Sometimes the penis is squeezed between the partner's thighs without being inserted into the body. This is called intercrural sex. Sometimes the penis is rubbed against the other person's body. The people can be naked or wearing clothes. When two males rub their penises together or against each other's body, it is called frottage. Ejaculation may also happen without touching during sleep (called a 'wet dream'). This is common, especially for pre-teen and teenage boys. It is uncommon in adults. While it can feel almost magical to ejaculate during a dream, boys don't like the mess it creates. Boys usually don't have wet dreams if they masturbate before sleeping every night. A male must have started puberty before he can ejaculate. (Sometimes when a boy who has not started puberty masturbates, a small amount of urine comes out.) During orgasm, muscles push semen from the penis. Semen moves through the urethra and comes out of the hole at the tip of the penis.

King Henry VIII - Google Art Project

Although in most modern societies the penis is usually hidden with some type of clothing, in earlier times, ideas were sometimes different. Sometimes the style was to have clothes clearly show that the penis was under the clothing. Fancy clothes that King Henry VIII wore in England hundreds of years ago might look strange today.

In many traditional societies in Africa and the South America, before Europeans came, men did not wear any clothing. Sometimes men wore a small piece of animal skin (now called a loincloth) in front of the penis. In hot temperatures in many parts of the world, men did not wear clothes. In Roman times, many slaves did not own any clothes. In ancient Greece, men competed in sports without clothes on.

In warm countries, it is a good idea to wear loose clothing to avoid skin problems with the penis or scrotum. Many boys and men sleep nude (without clothes.) This is normal and healthy, especially when the temperature is warm. Many boys and men prefer to swim without anything on. One hundred or two hundred years ago, boys and men usually would swim without any type of swimwear. People did not own bathing suits. Until the 1960s, it was required for boys and men to swim nude at many high school and YMCA pools[16][17] in the United States and Canada.

The current style for men's bathing suits (sometimes called swim trunks) in the United States and Canada is loose-fitting so other people cannot see the shape of the penis. Young boys and competitive swimmers and divers are usually the only males who wear tight swimwear in the United States and Canada. In Europe, males usually wear tight swimwear. At some places in Europe, loose fitting American style boardshorts and swim trunks are not allowed.

Some men put jewelry on their penis. This is a type of body piercing called genital piercing. One main reason is that it can make sex more pleasurable. Jewelry is sometimes at the tip (through the glans and urethra), sometimes through the foreskin, corona, or frenulum, or sometimes under the shaft of the penis. Some men put jewelry on the scrotum, mainly for decoration.