Gametogenesis is the production of haploid gametes by diploid multicellular organisms through the process of meiosis. The production of female gametes or ova (eggs) is called oogenesis. The production of male gametes or spermatozoa (sperm) is called spermatogenesis. Oogenesis occurs within the follicles of the ovaries. The meiosis of oocytes always results in halpoid cells of unequal size. When a primary oocyte undergoes meiosis, a large halpoid secondary oocyte and a very small first polar body result. A second meiotic division produces a large ootid and a very small second polar body. The first polar body may or may not divide during the second meiotic division into two additional second polar bodies. All the polar bodies are non-functional. After meiosis, the ootid quickly differentiates into the mature egg cell or ovum. The unequal cytokinesis that occurs has the advantage of providing the ovum with a much greater amount of cytoplasm and stored food than if an equal division were to occur. Thus, the non-motile ovum supplies a developing embryo with most of its cytoplasm and food while the much smaller but highly-motile sperm contributes mainly genetic material to the embryo.
Spermatogenesis occurs in the germinal epithelium which lines the seminiferous tubules in the testes. Epithelium cells or primary spermatocytes undergo two meiotic divisions producing four haploid cells of equal but minute size in comparison to the ovum, which conserves the original size of the primary oocyte through both meiotic divisions. During differentiation these haploid cells or
