ovogenees

Oogenesis is the process by which female gametes, or ova (eggs), are produced. This complex process begins during fetal development and continues throughout a woman's reproductive life. In the fetal ovary, primordial germ cells differentiate into oogonia. These oogonia then undergo mitotic divisions to increase their numbers. Following this proliferation, oogonia enter meiosis I and arrest in prophase I, becoming primary oocytes. These primary oocytes are surrounded by a layer of follicular cells, forming primordial follicles.

At puberty, under the influence of hormones, a small number of these primary oocytes resume meiosis I each menstrual cycle. Meiosis I completes, producing a large secondary oocyte and a small first polar body. The secondary oocyte begins meiosis II but arrests in metaphase II. If fertilization occurs, the secondary oocyte will complete meiosis II, yielding a mature ovum and a second polar body. If fertilization does not occur, the secondary oocyte degenerates. The polar bodies are non-functional and eventually disintegrate. Oogenesis ensures that a mature egg cell, capable of being fertilized, is produced at regular intervals.