GENERAL HISTOLOGY

Detailed explanation-1: -Female sex cells, or gametes, develop in the ovaries by a form of meiosis called oogenesis. The sequence of events in oogenesis is similar to the sequence in spermatogenesis, but the timing and final result are different. Early in fetal development, primitive germ cells in the ovaries differentiate into oogonia.

Detailed explanation-2: -Oogenesis occurs in the outermost layers of the ovaries. As with sperm production, oogenesis starts with a germ cell, called an oogonium (plural: oogonia), but this cell undergoes mitosis to increase in number, eventually resulting in up to one to two million cells in the embryo.

Detailed explanation-3: -In humans, a secondary oocyte is ovulated into the fallopian tube and metaphase II of meiosis does not complete until around the time of fertilization. Oogenesis is completed upon fertilization, where sperm penetrates the egg’s protective layer called the zona pellucida.

Detailed explanation-4: -Oogenesis begins before birth but is not finished until after puberty. A mature egg forms only if a secondary oocyte is fertilized by a sperm. Oogenesis begins long before birth when an oogonium with the diploid number of chromosomes undergoes mitosis. It produces a diploid daughter cell called a primary oocyte.

Detailed explanation-5: -Whereas spermatogenesis is initiated only at the time of puberty, oogenesis begins during a female’s development as a fetus (Fig. 2-17).