oogonier

An oogonier is a type of female germ cell found in the ovaries of female animals. These cells are diploid, meaning they contain two sets of chromosomes. Oogoniers are the precursor cells to oocytes, which are the cells that will eventually mature into eggs.

The development of oogoniers begins before birth in mammals. During fetal development, the female germ cells undergo rapid proliferation, forming a large number of oogoniers. These cells then begin the process of meiosis, a specialized type of cell division that reduces the chromosome number by half. However, the meiotic process is arrested in prophase I, and the oogoniers become primary oocytes.

After birth, the number of oogoniers declines. In many species, all oogoniers have either developed into primary oocytes or degenerated by the time of sexual maturity. During the reproductive years, a small number of primary oocytes will resume meiosis each menstrual cycle. This process leads to the formation of a secondary oocyte and a polar body. The secondary oocyte is the cell that, if fertilized by a sperm, will develop into a new individual.