Gametogenesis and gametes in males and females.

(a) In the process of spermatogenesis, male diploid (2n) germ cells undergo two meiotic divisions to produce mature haploid (n) sperm. (b) The characteristic head, midpiece, and tail of a mature human sperm, as seen in a drawing and the accompanying scanning electron micrograph (SEM). (c) The process of oogenesis in females, which produces a haploid secondary oocyte ready to be fertilized. (d) Mature oocyte. The drawing depicts a secondary oocyte within its follicle; the SEM shows an isolated human oocyte covered by its zona pellucida and remnants of the cumulus mass.