Male Reproductive System

Men's reproductive organs are mostly on the outside of the body. Here is a list.

Cowper's Glands: These two glands provide a clear thick fluid that lubricates the urethra when the penis is erect so that sperm can pass through. The urethra is the tube in the penis that carries semen or urine.

Epididymis: These coiled tubes are located at the back of the testes. Sperm move through these to be stored in the seminal vesicles.

Penis: External organ with a central tube called the urethra through which semen or urine leaves the body. The penis is made up of the shaft and the glans (head). The foreskin is a fold of skin that protects the glans (head) of the penis. The penis does not contain any bones or muscle but is made up of soft, spongy tissue that is full of blood vessels and lots of nerves. When a man is sexually excited, these vessels fill with blood. This causes the penis to enlarge and stiffen, which is called an erection. When semen comes out of the penis it is called ejaculation. Teenage boys often have erections even without sexual excitement. They also can release semen during the night ("wet dreams"). This is normal and common.

Prostate: A gland. This gland produces a fluid that becomes part of semen.

Seminal Vesicles: These glands, located behind the bladder, produce a fluid that forms part of semen. They are also storage areas for sperm.

Scrotum: The scrotum is the soft sac on the outside of the body that contains and protects the testicles. It is behind and underneath the penis. To protect sperm cells from temperature changes, muscles of the scrotum tighten when exposed to cold temperatures. This brings the testicles closer to the body. In warm weather, the scrotum hangs lower and the testicles seem larger - but there is actually no change in size of the testicles.

Sperm: Under a microscope, these male reproductive cells look like a tadpole, with a head and a tail. Sperm are produced in the testicles when puberty begins. Sperm cells swim in semen, a whitish, sticky liquid. Once a boy's body begins to produce sperm, he will produce millions daily for the rest of his life.

Testes/Testicles : In addition to sperm, these two glands also produce the male sex hormone testosterone. During puberty, the testicles become larger to allow the production of sperm. The testicles hang outside the body because sperm production requires a temperature slightly lower than body temperature. It is normal for the testicles to be slightly different sizes. New lumps or irregular areas on the testes should be checked by a doctor.

Urethra: This narrow tube running from the bladder through the penis is the passage for urine and semen. Semen and urine do not mix. That is because urine is automatically cut off when semen is being released.

Vas Deferens: These narrow tubes carry sperm from the epididymis, past the seminal vesicles, and into the prostate gland.

Last revised: April 21, 2008