第一步
精子產生的第一步始於生精小管最外層的細胞。這些細胞稱為原始的精原細胞，它們與體內的其他細胞一樣，含有46條染色體，包括一條X染色體和一條Y染色體。通過細胞分裂的方式，單個的原始生精細胞可以形成兩個同樣的姊妹細胞。姊妹細胞中的一個替代了原初的細胞，而另一個則移向生精小管的中央。後者被稱為初級精母細胞。

The First Step
The first step begins with the cells that lie closest to the outer edge of the tube. These cells are called primitive spermatogonia and, like any other cell in the body, they have 46 chromosomes, including an X chromosome and a Y chromosome. By means of cell division a single primitive spermatogonium forms two new identical daughter cells. One of these takes the place of the original cell, while the other moves toward the center of the tube. This latter cell is called the primary spermatocyte.