Anatomy of the penis and testicles

What you need to know about the sex organs of the male reproductive system, including illustrations


The penis and testicles, together with the scrotum form part of the sex organs of the male reproductive system (a collection of internal and external sex organs, which work together to allow all animals, including humans to reproduce and bear live offspring).  Due to its vital role in the survival of the species, many scientists argue that the reproductive system is among the most important systems in the entire body. This article gives a brief description of the penis, testicles and scrotum with the aid of an illustration of the sex organs of the male reproductive system.

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This is the male organ used in sexual intercourse. It has three parts:

  • the root, which attaches to the wall of the abdomen;
  • the body, or shaft; and
  • the glans, which is the cone-shaped part at the end of the penis.

The glans, also called the head of the penis, is covered with a loose layer of skin called the foreskin. This skin is sometimes removed in a procedure called circumcision. The opening of the urethra, the tube that transports semen and urine, is at the tip of the penis. The glans of the penis also contains a number of sensitive nerve endings.

The body of the penis is cylindrical in shape and consists of three circular shaped chambers. These chambers are made up of special, sponge-like tissue. This tissue contains thousands of large spaces that fill with blood when the man or intersex person is sexually aroused. As the penis fills with blood, it becomes rigid and erect, which allows for penetration during sexual intercourse. The skin of the penis is loose and elastic to allow changes in penis size during an erection.

Semen, which contains sperm (reproductive cells), is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm).  When the penis is erect, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.


Testicles or testes are oval organs about the size of large olives also known as gonads that lie in the scrotum (see below), secured at either end by a structure called the spermatic cord.  Most men have two testicles, which are responsible for making testosterone, the primary male sex hormone, and for producing sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubes are responsible for producing sperm cells.



The scrotum is the thin loose pouch-like sac of skin and thin muscle that hangs behind and below the penis. It contains the testicles or testes, as well as many nerves and blood vessels. The scrotum acts as a "climate control system" for the testicles, allowing them to be slightly away from the rest of the body and keeping them slightly cooler than normal body temperature for normal sperm development. Special muscles (cremasteric muscles) in the wall of the scrotum allows it to contract and relax, moving the testicles closer to the body for warmth or farther away from the body to cool them, depending on the surrounding temperature.



  1. emedicinehealth, Male Anatomy (Male Reproductive Organs), [website] 2019,, (accessed October 30, 2019).
  2. webMD, The Male Reproductive System, [website] 2019,, (accessed October 30, 2019).
  3. teenVOGUE, Mystery Solved: The Male Anatomy — OK, Penis — Broken Down for You, [website] 2015,, (accessed October 30, 2019).
  4. LIVESCIENCE, Reproductive System: Facts, Functions & Diseases, [website] 2018,, (accessed October 30, 2019).

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