Things You Should Know About the Penis

Discussing the penis is a sensitive subject that is usually not brought up in mixed company, and many men are uncomfortable and unlikely to discuss questions they might have with their doctor. Consequently, this article is designed to answer a few questions that many men (yes, and women, too) have possibly considered asking, but for whatever reason(s), never asked.

Does the penis have a mind of its own?

There are situations when a man may get an erection at an inappropriate time and the man may wish or desire not to have it, but it occurs anyway. Alternatively, there are some times when a man may want an erection but it does not occur. In these situations the penis acts like it has "a mind of its own."

When a penis becomes erect (or not) is controlled by information to it by parts of the nervous system that is not always under a man's conscious control. Two parts that may send messages to the penis independent of a man's conscious control are the autonomic and sympathetic nervous systems. A good example of "brain control" of the penis that is not voluntary (ie controlled by the person) is the erections that occur during sleep or the ones a man notices on occasion when he wakes up in the morning.

Voluntary input for man can influence an erection both positively and negatively, but the penis is influenced by other body nerve systems that, to a large extent, men have little or no control over. In addition, physiologic reactions (blood flow, exposure to cold environment, nerve damage) all interact and may affect the penis and its reaction to any given situation.

Let's talk penis size

Perhaps one of the more comprehensive studies of multiple sources of data on penile size is summarized in an article (reference 2) published by the Department of Urology at Weill Cornell Medical College as follows:

  • Average length of flaccid penis is between 3.4 inches and 3.7 inches (8.6 cm and 9.3 cm)
  • Average length of erect penis is between 5.1 inches and 5.7 inches (12.9 cm and 14.5 cm)
  • Average circumference of an erect penis is between 3.5 inches and 3.9 inches (8.8 cm and 10.0 cm)

Other studies provide additional information. For example, several studies show that some men have a flaccid penis that is about the length of an erect penis but when erect, gains little or no length while other men have a short flaccid penis but gain about twice its length when erect. Slang descriptions for a penis are numerous so for a longer flaccid penis, slang describe it as a "show-er" while one that is short but increases length markedly when erect is termed a "grow-er" but many are a combination of both. Consequently, the "show-er" may make the "grow-er" feel inadequate (especially in a High school locker room), but both types usually will produce a somewhat similar sized erection and so "grow-ers" should not feel inadequate. However, in some men, increased body fat, hormonal problems, certain surgeries and disease may decrease penis size.

Is the penis always straight during an erection?

The answer is that during an erection, the penis is more boomerang-shaped than straight, according to many MRI images taken during sex. The base of the penis is fixed by a ligament to the pubic bone (termed the suspensory ligament) and provides support for its upward angle and reduces movement at the base of the penis. This base area of the penis is inside the body; cutting the ligament can add a bit of length to a penis but the upward angle is lost as is the stability at the base.

Can you fracture or "break" the penis?

Slang for an erection is a "bone" or "boner" but the penis has no bony structures. Nonetheless, a person can still fracture or break a penis. This relatively rare break or fracture occurs (usually in younger men) when a man thrusts the penis to hard or fast into the partner's pelvic bone, or against hard resistance, the rigid penis can be stressed and fracture. What occurs when a penis is fractured is that the erectile portions of the penis lining, called the tunica albuginea, is torn (fractured or broken) by the stresses. When the tunica albuginea is torn, often there is an audible pop sound, the penis becomes flaccid and turns black and blue (due to blood leaking out of the erectile bodies into the surrounding tissue). This fracture is very painful and, because of potential complications, this fracture is considered a medical emergency.


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Why are the majority of US males circumcised?

Circumcision, the act of cutting off the penile foreskin, is commonly practiced in the US, especially by people of Jewish and Muslim decent or faith. About 65% to 70% of all US males are circumcised. The main reason this procedure was done in the past, as was speculated by medical historians, is to lessen or prevent urinary tract infections, phimosis (non-retractable foreskin) and paraphimosis (retracted foreskin that cannot return to its original position) in young males. Both phimosis and paraphimosis often are treated by circumcision, but circumcision done on older boys or an adult is much more complicated that infant circumcision. The practice of infant circumcision became part of the culture of many people and has been adopted by the majority of US citizens and doctors. Currently, the American Academy of Pediatrics and other medical societies have restated that no absolute medical indication for routine circumcision of the newborn exists.

However, most US parents (65% to 70%) still routinely do circumcisions and not for religious reasons. Why? There may be many reasons, including perceived cosmetically reasons, ease of care and because the father is circumcised. However, some recent studies may give some credence to the usefulness of the procedure. For example, recent studies indicated that 95% of young boys that developed urinary tract infections were uncircumcised. Five studies on penile cancer showed only uncircumcised males developed the disease, and several investigations have reported sexually transmitted diseases occurred more often in uncircumcised males.

Circumcised males are in the minority because worldwide, only about 30% of all males are circumcised.

Have most of your questions been answered? If not, see your local doctor or urologist for more details or look at the references listed below.

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Medically reviewed by Michael Wolff, MD; American Board of Urology

REFERENCES: Penile Fracture and Trauma.

Weill Cornel Medical College. Penis Size and Penis Enlargement.

Masters and Johnson. Human Sexual Response, Little, Brown, 1966. Wessels, H. Journal of Urology, September 1996; vol 156: pp 996-997. Jamison, P. Journal of Sex Research. 1988; vol 24: pp 177-183.

Faix, A. et al. Magnetic Resonance Imaging (MRI) of Sexual Intercourse: Second Experience in Missionary Position and Initial Experience in Posterior Position. Journal of Sex and Marital Therapy. 2002; vol 28: pp 63-76.

WHO and UNAIDS: Male circumcision: Global trends and determinants of prevalence, safety and acceptability. (42 pp; 191 refs). 2008a. Geneva, World Health Organization.