The Sex Organs - The Male Sex Organs

The Internal Sex Organs: The Production of Sperm

3. The Third Step
The two secondary spermatocytes move even closer to the center of the tube, and each divides again in the ordinary fashion, duplicating itself exactly. The four new cells are called spermatids. These spermatids now change their shape, develop a tail, and thus grow into mature sperm cells called spermatozoa. The entire process through all three stages of development takes about 64 days. As is obvious from their origin and development, spermatozoa come in two varieties: those containing an X chromosome (and 22 other chromosomes), and those containing a Y chromosome (and 22 other chromosomes). In case of a fertilization the X-bearing spermatozoa will help to produce girls; the Y-bearing spermatozoa will help to produce boys.

Inside a seminiferous tubule.
1. spermatogonium 2. primary spermatocyte 3. secondary spermatocyte
4. spermatids 5. cell division 6. interstitial cells producing testosterone 7. sperm cells