Problems with the penis can cause pain and affect a man's sexual function and fertility. Penis disorders include

• Erectile dysfunction - inability to get or keep an erection
• Priapism - a painful erection that does not go away
• Peyronie's disease - bending of the penis during an erection due to a hard lump called a plaque
• Balanitis - inflammation of the skin covering the head of the penis, most often in men and boys who have not been circumcised
• Penile cancer - a rare form of cancer, highly curable when caught early

The Penis

The penis is the male organ of copulation (sexual intercourse). It is flaccid for non-sexual actions, such as urination, and turgid and rod-like with sexual arousal. When erect, the stiffness of the organ allows it to penetrate into the vagina and deposit semen into the female reproductive tract.

The shaft of the penis surrounds the urethra (Figure). The shaft is composed of three column-like chambers of erectile tissue that span the length of the shaft. Each of the two larger lateral chambers is called a corpus cavernosum (plural = corpora cavernosa). Together, these make up the bulk of the penis. The corpus spongiosum, which can be felt as a raised ridge on the erect penis, is a smaller chamber that surrounds the spongy, or penile, urethra. The end of the penis, called the glans penis, has a high concentration of nerve endings, resulting in very sensitive skin that influences the likelihood of ejaculation (see Figure). The skin from the shaft extends down over the glans and forms a collar called the prepuce (or foreskin). The foreskin also contains a dense concentration of nerve endings, and both lubricate and protect the sensitive skin of the glans penis. A surgical procedure called circumcision, often performed for religious or social reasons, removes the prepuce, typically within days of birth.

Both sexual arousal and REM sleep (during which dreaming occurs) can induce an erection. Penile erections are the result of vasocongestion, or engorgement of the tissues because of more arterial blood flowing into the penis than is leaving in the veins. During sexual arousal, nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and spongiosum. Release of NO activates a signaling pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing them to dilate. This dilation increases the amount of blood that can enter the penis and induces the endothelial cells in the penile arterial walls to also secrete NO and perpetuate the vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin-walled penile venules, preventing venous drainage of the penis. The result of this increased blood flow to the penis and reduced blood return from the penis is erection. Depending on the flaccid dimensions of a penis, it can increase in size slightly or greatly during erection, with the average length of an erect penis measuring approximately 15 cm.

Disorders of the Male Reproductive System: Erectile Dysfunction (ED)

Erectile dysfunction (ED) is a condition in which a man has difficulty either initiating or maintaining an erection. The combined prevalence of minimal, moderate, and complete ED is approximately 40 percent in men at age 40, and reaches nearly 70 percent by 70 years of age. In addition to aging, ED is associated with diabetes, vascular disease, psychiatric disorders, prostate disorders, the use of some drugs such as certain antidepressants, and problems with the testes resulting in low testosterone concentrations. These physical and emotional conditions can lead to interruptions in the vasodilation pathway and result in an inability to achieve an erection.

Recall that the release of NO induces relaxation of the smooth muscles that surround the penile arteries, leading to the vasodilation necessary to achieve an erection. To reverse the process of vasodilation, an enzyme called phosphodiesterase (PDE) degrades a key component of the NO signaling pathway called cGMP. There are several different forms of this enzyme, and PDE type 5 is the type of PDE found in the tissues of the penis. Scientists discovered that inhibiting PDE5 increases blood flow, and allows vasodilation of the penis to occur.

PDEs and the vasodilation signaling pathway are found in the vasculature in other parts of the body. In the 1990s, clinical trials of a PDE5 inhibitor called sildenafil were initiated to treat hypertension and angina pectoris (chest pain caused by poor blood flow through the heart). The trial showed that the drug was not effective at treating heart conditions, but many men experienced erection and priapism (erection lasting longer than 4 hours). Because of this, a clinical trial was started to investigate the ability of sildenafil to promote erections in men suffering from ED. In 1998, the FDA approved the drug, marketed as Viagra^®. Since approval of the drug, sildenafil and similar PDE inhibitors now generate over a billion dollars a year in sales, and are reported to be effective in treating approximately 70 to 85 percent of cases of ED. Importantly, men with health problems—especially those with cardiac disease taking nitrates—should avoid Viagra or talk to their physician to find out if they are a candidate for the use of this drug, as deaths have been reported for at-risk users.

What is circumcision?

Circumcision is a surgical procedure to remove the foreskin, the skin that covers the tip of the penis. In the United States, it is often done before a new baby leaves the hospital. According to the American Academy of Pediatrics (AAP), there are medical benefits and risks to circumcision.

What are the medical benefits of circumcision?

The possible medical benefits of circumcision include

• A lower risk of HIV
• A slightly lower risk of other sexually transmitted diseases
• A slightly lower risk of urinary tract infections and penile cancer. However, these are both rare in all males.

What are the risks of circumcision?

The risks of circumcision include

• A low risk of bleeding or infection
• Pain. AAP suggests that providers use pain medicines to reduce pain from circumcision.

What are the American Academy of Pediatrics (AAP) recommendations on circumcision?

The AAP does not recommend routine circumcision. However, they said that because of the possible benefits, parents should have the option to circumcise their sons if they want to. They recommend that parents discuss circumcision with their baby's health care provider. Parents should make their decision based on the benefits and risks, as well as their own religious, cultural, and personal preferences.

Erectile dysfunction (ED) is a common type of male sexual dysfunction. It is when a man has trouble getting or keeping an erection. ED becomes more common as you get older. But it's not a natural part of aging.

Some people have trouble speaking with their doctors about sex. But if you have ED, you should tell your doctor. ED can be a sign of health problems. It may mean your blood vessels are clogged. It may mean you have nerve damage from diabetes. If you don't see your doctor, these problems will go untreated.

Your doctor can offer several new treatments for ED. For many men, the answer is as simple as taking a pill. Getting more exercise, losing weight, or stopping smoking may also help.

Infertility is a term doctors use if a man hasn't been able to get a woman pregnant after at least one year of trying. Causes of male infertility include

• Physical problems with the testicles
• Blockages in the ducts that carry sperm
• Hormone problems
• A history of high fevers or mumps
• Genetic disorders
• Lifestyle or environmental factors

About a third of the time, infertility is because of a problem with the man. One third of the time, it is a problem with the woman. Sometimes no cause can be found.

If you suspect you are infertile, see your doctor. There are tests that may tell if you have fertility problems. When it is possible to find the cause, treatments may include medicines, surgery, or assisted reproductive technology. Happily, many couples treated for infertility are able to have babies.

What are sexually transmitted infections (STIs)?

Sexually transmitted infections (STIs), or sexually transmitted diseases (STDs), are infections that are passed from one person to another through sexual contact. They are usually spread during vaginal, oral, or anal sex. But sometimes they can spread through other sexual contact involving the penis, vagina, mouth, or anus. This is because some STIs, like herpes and HPV, are spread by skin-to-skin contact.

Some STIs can be passed from a pregnant person to the baby, either during pregnancy or when giving birth. Other ways that some STIs may be spread include during breastfeeding, through blood transfusions, or by sharing needles.

There are more than 20 types of STIs, including:

• Chlamydia
• Genital herpes
• Gonorrhea
• HIV
• HPV
• Pubic lice
• Syphilis
• Trichomoniasis

What causes sexually transmitted infections (STIs)?

STIs can be caused by bacteria, viruses, and parasites.

Who is affected by sexually transmitted infections (STIs)?

Most STIs affect both men and women, but in many cases the health problems they cause can be more severe for women. If an STI is passed to a baby, it can cause serious health problems.

What are the symptoms of sexually transmitted infections (STIs)?

STIs don't always cause symptoms or may only cause mild symptoms. So it is possible to have an infection and not know it. And even without symptoms, STIs can still be harmful and may be passed on during sex.

If there are symptoms, they could include:

• Unusual discharge from the penis or vagina
• Sores or warts on the genital area
• Painful or frequent urination (peeing)
• Itching and redness in the genital area
• Blisters or sores in or around the mouth
• Abnormal vaginal odor
• Anal itching, soreness, or bleeding
• Abdominal (belly) pain
• Fever

How are sexually transmitted infections (STIs) diagnosed?

If you are sexually active, you should talk to your health care provider about your risk for STIs and whether you need to be tested. This is especially important since many STIs do not usually cause symptoms.

Some STIs may be diagnosed during a physical exam or through STI testing. Some tests involve a microscopic examination of a sore or fluid swabbed from the vagina, penis, or anus. Blood tests can diagnose other types of STIs.

What are the treatments for sexually transmitted infections (STIs)?

Antibiotics can treat STIs that are caused by bacteria or parasites. There is no cure for STIs caused by viruses, but antiviral medicines can often help with the symptoms and lower your risk of spreading the infection.

It's important to get treatment if you have an STI. Some types of STIs can cause serious health problems if they are not treated.

Can sexually transmitted infections (STIs) be prevented?

The surest way to protect yourself against STIs is to not have sex.

If you do decide to have sex, you can lower your risk of getting an STI by:

• Having you and your partner tested for STIs before having sex.
• Using a condom every time you have sex. Correct usage of latex condoms greatly reduces, but does not completely eliminate, the risk of catching or spreading STIs. If your or your partner is allergic to latex, you can use polyurethane condoms.
• Reducing your number of sex partners. You might even consider "mutual monogamy" with just one partner. This means that you agree to be sexually active only with them, and they agree to be sexually active only with you. But first you should both get tested to make sure that you don't already have an STI.
• Getting vaccinated against HPV and hepatitis B.

Testicles, or testes, make male hormones and sperm. They are two egg-shaped organs inside the scrotum, the loose sac of skin behind the penis. It's easy to injure your testicles because they are not protected by bones or muscles. Men and boys should wear athletic supporters when they play sports.

You should examine your testicles monthly and seek medical attention for lumps, redness, pain or other changes. Testicles can get inflamed or infected. They can also develop cancer. Testicular cancer is rare and highly treatable. It usually happens between the ages of 15 and 40.

Pathological processes involving the penis or its component tissues.

Inflammation of the head of the penis, glans penis.

A birth defect due to malformation of the urethra in which the urethral opening is below its normal location. In the male, the malformed urethra generally opens on the ventral surface of the penis or on the perineum. In the female, the malformed urethral opening is in the vagina.

A condition characterized by hardening of the penis due to the formation of fibrous plaques on the dorsolateral aspect of the penis, usually involving the membrane (tunica albuginea) surrounding the erectile tissue (corpus cavernosum penis). This may eventually cause a painful deformity of the shaft or constriction of the urethra, or both.

A condition in which the foreskin cannot be retracted to reveal the glans penis. It is due to tightness or narrowing of the foreskin opening.

A prolonged painful erection that may lasts hours and is not associated with sexual activity. It is seen in patients with sickle cell anemia, advanced malignancy, spinal trauma; And certain drug treatments.