Picture of the penis
The penis is made of several parts:
- Glans (head) of the penis. In uncircumcised men the glans is covered with pink, moist tissue called mucosa. Covering the glans is the foreskin (prepuce). In circumcised men the foreskin is surgically removed and the mucosa on the glans transforms into dry skin.
- Corpus cavernosum. Two columns of tissue running along the sides of the penis. Blood fills this tissue to cause an erection.
- Corpus spongiosum. A column of sponge-like tissue that surrounds the urethra in the penis and ending at the glans penis; it fills with blood during an erection, keeping the urethra - which runs through it - open.
- The urethra runs through the corpus spongiosum, conducting urine out of the body.
An erection results from changes in blood flow in the penis. When a man becomes sexually aroused, nerves cause penis blood vessels to expand. More blood flows in and less flows out of the penis, hardening the tissue in the corpus cavernosum.
- Erectile dysfunction. A man's penis does not achieve sufficient hardness or an erection doesn’t last long enough for satisfying intercourse. Atherosclerosis (narrowing of the arteries) is the most common cause of erectile dysfunction.
- Priapism. An abnormal erection that does not go away after several hours even though stimulation has stopped. Serious problems can result from this painful condition.
- Hypospadias. A birth defect in which the opening for urine is on the front (or underside), rather than the tip of the penis. Surgery can correct this condition.
- Phimosis (paraphimosis). The foreskin cannot be retracted or if retracted cannot be returned to its normal position over the penis head. In adult men this can occur after penis infections.
- Balanitis. Inflammation of the glans penis, usually due to infection. Pain, tenderness and redness of the penis head are symptoms.
- Balanoposthitis. Balanitis that also involves the foreskin (in an uncircumcised man).
- Chordee. An abnormal curvature of the end of the penis, present from birth. Severe cases may require surgical correction.
- Peyronie’s Disease. An abnormal curvature of the shaft of the penis may be caused by injury of the adult penis or other medical conditions.
- Urethritis. Inflammation or infection of the urethra, often causing pain with urination and penis discharge. Gonorrhoea and chlamydia are common causes.
- Gonorrhoea. The bacteria Neisseria gonorrhoeae infects the penis during sex, causing urethritis. Most cases of gonorrhoea in men cause symptoms of penis pain or discharge.
- Chlamydia. A bacterium that can infect the penis through sex, causing urethritis. Around 50% of chlamydia cases in men cause no symptoms.
- Syphilis. A bacterium transmitted during sex. The initial symptom of syphilis is usually a painless ulcer (chancre) on the penis.
- Herpes. The viruses HSV-1 and HSV-2 can cause small blisters and ulcers on the penis that can reoccur over time.
- Micropenis. An abnormally small penis, present from birth. A hormone imbalance is involved in many cases of micropenis.
- Penile warts. The human papillomavirus (HPV) can cause genital warts on the penis. HPV warts are highly contagious and spread during sexual contact.
- Penile cancer. Cancer of the penis is very rare in the UK Circumcision decreases the risk of penis cancer.