Normal testicular function and spermatogenesis.

The testis performs two basic functions, sperm production and testosterone secretion. Formation of the testis is genetically controlled; expression of the SRY gene directs the embryonic gonads into the pathway leading to the development of testes. By the fourth week of gestation in humans, the primordial germ cells derived from pluripotent cells of the embryonic epiblast proliferate and migrate from the endoderm of the yolk sac into the undifferentiated gonad, which becomes morphologically distinct during the seventh week of gestation in humans. Histological development of the testis is largely completed by the end of the third month of gestation. (c) 2009 Wiley-Liss, Inc.