Male Reproductive System

The organs of the male reproductive system are specialized for the following functions:

• To produce, maintain and transport sperm (the male reproductive cells) and protective fluid (semen)
• To discharge sperm within the female reproductive tract
• To produce and secrete male sex hormones

The male reproductive anatomy includes internal and external structures.


What are the external reproductive structures?

"Most of the male reproductive system is located outside of the man’s body. The external structures of the male reproductive system are the penis, the scrotum and the testicles."

1. Penis

The penis consists of the root (which is attached to the lower abdominal structures and pelvic bones), the visible part of the shaft, and the glans penis (the cone-shaped end). The opening of the urethra (the channel that transports semen and urine) is located at the tip of the glans penis. The base of the glans penis is called the corona. In uncircumcised males, the foreskin (prepuce) extends from the corona to cover the glans penis. The penis includes three cylindrical spaces (blood-filled sinuses) of erectile tissue. The two larger ones, the corpora cavernosa, lie side-by-side. The third sinus, the corpus spongiosum, surrounds most of the urethra. When these spaces fill with blood, the penis becomes large and rigid (erect).

2. Scrotum

The scrotum is the loose pouch-like sac of skin that hangs behind the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum has a protective function and acts as a climate control system for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than the body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth and protection or farther away from the body to cool the temperature.

3. Testicles (testes)

The testes are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubules are responsible for producing the sperm cells through a process called spermatogenesis.

4. Epididymis

The epididymis consists of a single coiled microscopic tube that measures almost 20 feet (6 meters) in length. The epididymis collects sperm from the testis and provides the environment for sperm to mature and acquire the ability to move through the female reproductive system and fertilize an ovum. One epididymis lies against each testis.

What are the internal reproductive organs?

"The internal organs of the male reproductive system, also called accessory organs, include the following:"

• Ejaculatory ducts — These are formed by the fusion of the vas deferens and the seminal vesicles. The ejaculatory ducts empty into the urethra.

• Urethra — The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of expelling (ejaculating) semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.

• Seminal vesicles — The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy and helps with the sperms’ motility (ability to move). The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fl id, or ejaculate.

• Prostate gland — The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of th prostate gland.

• Bulbourethral glands — The bulbourethral glands, or Cowper’s glands, are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra.