oogenese

Oogenese is the process by which oocytes, or immature female gametes, are produced in the ovary. This process begins before birth and continues through a female's reproductive years. The initial stage involves a large number of primordial germ cells that differentiate into oogonia. These oogonia then undergo mitotic divisions to increase their numbers. Following this proliferative phase, oogonia enter meiosis I, becoming primary oocytes. These primary oocytes are arrested in prophase I of meiosis and remain in this state until puberty.

At the onset of puberty, hormonal signals trigger the resumption of meiosis I in a select group of primary oocytes each menstrual cycle. This division results in one secondary oocyte and a small polar body. The secondary oocyte proceeds into meiosis II but is arrested at metaphase II. If fertilization occurs, the secondary oocyte completes meiosis II, producing a mature ovum and a second polar body. If fertilization does not occur, the secondary oocyte degenerates. Oogenese is characterized by unequal cytoplasmic division, ensuring that the ovum receives ample nutrients for potential embryonic development. This process is crucial for female reproduction.