To describe the process by which gametes are produced. Gametogenesis To describe the process by which gametes are produced.

What is Gametogenesis? This is the process by which sex cells are made. Meiosis is the production of sex cells. Meiosis is different in males and females.

Spermatogenesis This is the formation of Sperm Cells. In males, each cell formed becomes a sperm cell. This happens by the process of meiosis in an uninterrupted sequence. The process occurs in adult males, producing as many as 250 – 400 million sperm cells in each ejaculation (± 5ml).

Spermatogenesis

OOgenesis This is the formation of ova or egg cells. Oogenesis differs from spermatogenesis in a number of ways. During the first meiotic division, cytokinesis is uneven, one cell takes all the cytoplasm. This large cell goes on to form the egg, the smaller cell forms polar bodies, which disintegrate.

OOgenesis Cont At birth the ovary has all the cells it will ever have to develop into eggs. The formation of the eggs involves long “resting periods”. Between birth and puberty, the egg cells enlarge and the follicles around them grow. The primary egg cells replicate their DNA, they enter Prophase 1 but do not change again until reactivated by hormones at puberty.

OOgenesis Cont After puberty, an egg cell stimulated by hormones, periodically completes meiosis 1 and then stops. This is the form in which it is released in the menstrual cycle. Penetration of the sperm cell triggers the second meiotic division in humans.

OOgenesis

Summary