Gametocytes are eukaryotic germ line cells. They can undergo mitosis to form more gametocytes or undergo meiosis to form gametids. Male gametocytes are called spermatocytes and female gametocytes are called oocytes.

Spermatocytes are male gametocytes located in the seminiferous tubules of the testes. Primary spermatocytes are diploid and form when spermatogonia—immature germ cells—enter into mitosis. Primary spermatocytes can then enter meiosis and produce haploid secondary spermatocytes after meiosis I.

Secondary oocytes are haploid cells that are produced by primary oocytes through meiosis in a process called ootidogenesis. Secondary oocytes remain arrested in the metaphase II stage of meiosis until fertilization, when ootidogenesis is completed. The process of ootidogenesis also produces polar bodies.

Spermatogonia are diploid undifferentiated male germ cells located in the seminiferous tubules of the testes. Spermatogonia are important in the process of spermatogenesis; they turn into primary spermatocytes via growth and maturation.

Mature sperm cells that are haploid, motile, and produced during spermatogenesis are called spermatozoa. Spermatids are haploid; however, they are immature. Spermatids will turn into spermatozoa once they mature.

Ootidogenesis is the production of secondary ooctyes from primary ooctyes through meiosis. Ootidogenesis features two periods of developmental arrest—dictyate—during the prophase I stage of meiosis I and during metaphase II of meiosis II. The dictyate stage of arrest ends at the onset of puberty due to a spike in luteinizing hormone (LH) levels. Ootidogenesis then continues until the second arrest period during metaphase II. This period ends at fertilization and allows the completion of ootidogenesis.

Spermatogenesis—the formation of spermatozoa—occurs in the seminiferous tubules of the testes. Seminiferous tubules are composed of Sertoli cells and spermatogenic cells. There is a high concentration of testosterone present in these tubules. High testosterone concentrations support sperm development. The epididymis is the site of sperm maturation. Last, the seminal vesicles are small glands that produce the majority of the seminal fluid.

Polar bodies are haploid cells produced during ootidogenesis. They are smaller than secondary oocytes due to asymmetric cell division. During asymmetrical cell division a smaller volume of cytoplasm is partitioned into the polar bodies than to the secondary oocytes. This makes polar bodies not viable for fertilization. Polar bodies are often degraded, but they can also remain in the human body.

Oogenesis, or the formation of egg cells, takes place in the ovaries. Specifically, oogenesis takes place in the follicles—a pack of cells surrounding developing oocytes that is located within the ovaries.

Spermatozoa are stored in the epididymis prior to ejaculation. Prior to entering the epididymis, spermatozoa are immotile; however, as they travel through the epididymis the cells mature and gain motility.