Anatomy of the Penis


The penis acts as the male sex organ as well as the route through which urine, semen, and pre-ejaculate leave the body.1 Penis shape and size differs widely between males. Over the course of puberty, which generally begins in young males between the ages of 9 to 14, the penis grows and develops significantly until it reaches its final adult size.2 Many parts of the penis, including the glans, frenulum, shaft, and foreskin can be stimulated via masturbation, oral sex, or other forms of stimulation even to the point of orgasm.

Diagram of the anatomy of a penis.
A drawn penis. A person's hands are lifting the penis' foreskin.


The glans, or head, of the penis is the cone-shaped structure at the tip of the penis. It contains 4,000 nerve endings, causing it to be highly sensitive to the touch.2


The foreskin is a thin flap of skin that completely covers the glans unless it is pulled back. Upon arousal and erection, the foreskin typically pulls back to expose the glans.  Many men receive a circumcision at birth, which means that the foreskin has been removed.3 There is no scientific evidence to support the idea that foreskin adds to or detracts from sexual pleasure, but many parents wish to circumcise their male child as a religious rite or for increased hygiene. If the glans under the foreskin is not cleaned properly, there is a chance that bacteria, dead skin, and oil, also known as smegma, will accumulate. Smegma may increase the risk of a bacterial infection.1


The urethra runs through the corpus spongiusum.1 The urethra allows urine from the bladder and ejaculate from the prostate, seminal vesicles, and testes to flow out of the body. The structure within the urethra allows for urine to flow from the penis in a steady stream that is relatively easy to control. There is also a sphincter within the urethra that controls the flow of fluids, just like a tightened muscle constricts blood flow. The urethra also controls the type of fluid that is allowed to run out of the body via the urethral opening.1

Urethral Opening

The urethral opening is the tiny slit at the top of the penis through which urine and ejaculate leave the body.1 Other bodily fluids and secretions may exit the body via the urethra as a result of a sexually transmitted infection (STI).2 For example, if urine were leaving the penis, then ejaculate would be blocked, as the sphincter at the base of the urethra would not allow for those fluids to mix and exit the body simultaneously.2


The frenulum is the small strip of skin that runs from the glans to the shaft.1 It is considered to be one of the most sensitive places on the penis. Since the frenulum is so incredibly sensitive, sensations can range from intense feelings of pleasure to extreme discomfort, depending on the intensity and duration of stimulation.2

A digram of the anatomy of a penis and scrotum.


The corona is the piece of skin that separates the glans from the penis shaft and creates a ridge.


The shaft is the long, cylindrical part of the penis that connects the glans to the base. It is made up of three parts: two corpora cavernosa and the corpus spongiosum, which all fill up with blood as the penis develops an erection.3 Length and girth are variable and do not correspond directly to a change in sexual pleasure. Although there is an average value given to both length and girth, it is completely normal to have a variation.

Corpora Cavernosa

Also known as the cavernous bodies, the corpora cavernosa are two of the three chambers within the shaft of the penis that fill up with blood upon sexual arousal, thus causing an erection, as they are becoming firm and rigid. These bodies extend from the base of the shaft to the glans. The corpora cavernosa can also become engorged with blood as a result of hormonal changes during the early stages of puberty.2

Corpus Spongiosum

Also known as the spongy body, this tissue composes the glans of the penis. The corpus spongiosum also runs along the underside of the shaft and encircles the urethra. As the erection develops, the corpus spongiosum fills with blood and allows the urethra to remain open so that ejaculate and other fluids can be released from the body. It can be seen as a raised, vein-like column along the underside of the penis. In contrast to the corpora cavernosa, the corpus spongiosum is a much more flexible body that does not become as rigid. It regulates the amount of blood that enters so that the urethra can remain open.2


The base or bulb of the penis is a rounded mass of tissue at the base of the corpus spongiosum. The base of the penis is located above the scrotum and connects the penis to the abdomen.2


The root of the penis connects the shaft of the penis and all of its internal structures to the pelvic bones via strong ligaments in order to hold it in place.3


A loose sac of skin that hangs below the penis and holds both of the testes. The distance that the scrotal sac hangs below the body changes with temperature.3 For example, when the body is cold, the scrotum pulls up towards the penis and pelvis in order to keep the testes warmer. When the body is hot, the scrotum drops down lower in an attempt to cool the testes. This movement is crucial because the testes need to be kept 5 degrees cooler than normal body temperature (98.6oF), for most effective sperm production.

Penile Skin

The penile skin is continuous with the skin of the lower abdomen. The glans is covered with smooth, hairless skin.  Below the glans, at the corona, the skin folds onto itself to form the foreskin, which lies on top of the glans when flaccid if the male is uncircumcised (circumcised men lack foreskin). The penile skin is attached loosely to the smooth muscle tissue beneath it.3 The penile skin contains millions of sensitive nerve endings which allow for the penis to be easily aroused upon a gentle touch.2

Concluding Remarks

The penis is an intricate sex organ that is essential to the reproduction process. With good communication, the penis can also be a source of immense sexual pleasure. For more information, check out our article on the overview of the male reproductive system as well as other articles about erectile dysfunction and proper care and protection of the penis.

Check out this great video about the penis!


  1. Hoffman, Matthew. Picture of the Penis. Web MD. 2014. Web.
  2. LeVay, Simon, Janice I. Baldwin, and John D. Baldwin. Discovering Human Sexuality. Sunderland, MA: Sinauer Associates, 2009. Print.
  3. Taylor, Tim. Penis. Inner Body. 2017. Web.

Last Updated: 07 October 2017.