The penis is a complex external organ in males used to urinate and for sex and reproduction. It consists of several parts, including the shaft, head, and foreskin. This article describes the anatomy and function of the penis as well as conditions that can affect the function or appearance of the penis at birth or later in life.
The penis is located at the front of the body at the base of the pelvis. The scrotum , containing the testicles, lies below the penis. The penis consists of several major structures:. The penis is well supplied by blood vessels. The shaft, which contains the urethra and three columns of erectile tissue, is wrapped in a band of connective tissue called the fascia and covered with skin.
The base of the penis is supported by connective tissues, called suspensory ligaments, that hold the penis close to the pelvic bone. The average flaccid "soft" length of a penis is 3. The average length of an erect penis is 6 inches with an average circumference of 5 inches.
The penis is made up of the corpus shaft , glans head , and prepuce foreskin. The urethra is a tube through which urine or semen exits the body. The spongy columns of tissue within the shaft can fill with blood and cause an erection.
The primary functions of the penis are urinary and sexual. The sexual function of the penis can be further broken down into two stages: erection and ejaculation. Urination is the release of urine from the body. This occurs when urine passes from the bladder through the urethra to the meatus. The urine is pushed out of the body by the contraction of the detrusor muscle in the wall of the bladder. At the root of the penis is the external sphincter muscle , which males can control to hold in or release urine.
It is also normal for erections to occur during sleep and upon waking. An erection occurs when there is an increased flow of blood into the corpus cavernosa and corpus spongiosum. During an erection, arteries supplying the erectile tissues will dilate widen , causing the penis to engorge fill with blood.
The engorgement compresses the veins through which blood usually exits the penis. This "traps" the blood and helps sustain the erection. Ejaculation is the discharge of semen from the body.
It is usually accompanied by a sexual response called an orgasm. Ejaculation involves a series of simultaneous, involuntary muscle contractions:. The primary functions of the penis are urination, erection, and ejaculation. Each involves a complex series of involuntary and voluntary processes. There are several congenital conditions that can cause a penis to be abnormally formed.
Congenital disorders are those that are present at birth and caused when something interferes with the normal development of an unborn baby. Congenital penis abnormalities are usually caused by an imbalance of hormones that influence penis development.
Hypospadias is a condition where the opening of the urethra is on the underside of the penis rather than at the tip. It is one of the most common congenital abnormalities in males. Epispadias is a similar condition in which the urethra opens on the top side of the penis. Surgery is generally recommended to correct hypospadias either during infancy or early childhood.
However, there are risks of long-term complications, including difficulty urinating and an increased risk of urinary tract infections. Chordee is an abnormal curve of the penis at the time of birth. It is more common in males with hypospadias but can also occur on its own. In adolescent and adult males, chordee is most noticeable during an erection.
Chordee should not be confused with Peyronie's disease. Peyronie's is a condition that develops in adult males that causes an abnormal curve of the penis.
Micropenis is an abnormally small penis. It is defined as a stretched penis that is at least 2. In adults, this would be stretched penis of less than 2. Micropenis affects 1. It is thought the be caused by abnormally low production of male hormones, called androgens , during pregnancy. The congenital absence of a penis, called aphalia, is an extremely rare condition, affecting one of every 30 million births.
It usually occurs with other congenital abnormalities affecting the heart or digestive tract. Search Search. Search Tips Use the search page for more options Use quotation marks e.
Use multiple keywords separated by spaces e. This search will retrieve items that correspond to any of those words, ranking higher those with all or most of the keywords. Robbins and Cotran Pathologic Basis of Disease. Philadelphia, PA: Elsevier Saunders; chap Management of abnormalities of the external genitalia in boys. Campbell-Walsh Urology. Penis and scrotum. Urologic Surgical Pathology. Updated by: Sovrin M. Using Trusted Resources.
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