Sperm

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Sperm is the name given to the male sex cells. The tissue which produces the male sex cells (the germinal epithelium) consists of two types of cells: supporting cells (Sertoli's cells) and spermatogenic cells. The supporting cells are tall, columnar cells that extend the full thickness of the epithelium from its base to the lumen of the seminiferous tubule. In a young male, all the spermatogenic cells are of one class and are called spermatogonia. Each of these contain forty-six chromosomes in its nucleus. During early adolescence, certain hormones stimulate spermatogonia to become active. Some undergo mitosis (dividing into two daughter cells), giving rise to new spermatogonia and providing a reserve supply. Others enlarge and become primary spermatocytes that then divide by a special type of cell division called meiosis. In the course of meiosis, the primary spermatocytes each divide to form two secondary spermatocytes. Each of these cells, in turn, divides to form two spermatids, which mature into sperm cells. The process by which sperm cells are produced is called spermatogenesis.