http://www.ck12.org Chapter 1. Human Biology
FIGURE 1.129
This drawing of a sperm shows its main
parts. What is the role of each part? How
do you think the shape of the sperm might
help it swim?Sperm Production
To make sperm, cells start in the testes and end in the epididymis. It takes up to two months to make sperm. The
steps are explained below:
- Special cells in the testes go throughmitosis(cell division) to make identical copies of themselves.
- The copies of the original cells divide bymeiosis, producing cells calledspermatids. The spermatids have
half the number of chromosomes as the original cell. The spermatids are immature and cannot move on their
own. - The spermatids are transported from the testes to the epididymis. Involuntary muscular contraction moves the
spermatids along. - In theepididymis, spermatids slowly grow older and mature. They grow a tail. They also lose some of the
cytoplasm from the head. - When sperm are mature, they can “swim.” The mature sperm are stored in the epididymis until it is time for
them to leave the body.
Sperm leave the epididymis through thevas deferens. As they travel through the vas deferens, they pass by the
prostate and other glands. The sperm mix with liquids from these glands, formingsemen. The semen travels
through the urethra and leaves the body through the penis. A teaspoon of semen may contain as many as 500 million
sperm!
Vocabulary
- epididymis: Male reproductive organs where sperm mature and are stored until they leave the body.
- meiosis: Process in cell division during which chromosome number is halved in order to produce gametes.
- mitochondria: Organelle of the cell in which energy is generated.
- mitosis: Division of the nucleus.
- nucleus: Eukayrotic cell structure that contains the genetic material, DNA.
- sperm: Male gamete, or reproductive cell.
- spermatid: Non-motile cell in the sperm maturation process that has half the number of chromosomes of the
original cell.