Describe the process of oogenesis.

Oogenesis is the process by which female gametes, or eggs, are produced in the ovaries. It begins before birth, when primordial germ cells in the ovaries undergo mitosis to produce oogonia. These oogonia then undergo meiosis to become primary oocytes, which are arrested in prophase I of meiosis until puberty.

During each menstrual cycle, a few primary oocytes are stimulated to resume meiosis and develop into secondary oocytes. This process is regulated by hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH) released by the pituitary gland. The secondary oocyte is released from the ovary during ovulation and is surrounded by a layer of granulosa cells called the cumulus oophorus.

If the secondary oocyte is fertilized by a sperm cell, it completes meiosis II to become a mature ovum. If fertilization does not occur, the secondary oocyte degenerates. The mature ovum contains half of the genetic material needed to create a new individual, and it is capable of being fertilized by a sperm cell to form a zygote.

Overall, oogenesis is a complex process that involves the production and maturation of female gametes in the ovaries, ultimately leading to the formation of a mature ovum that can be fertilized.