Describe oogenesis with respect to the timing of the processes and the number and type of cells finally produced.

Question: Describe the process of oogenesis, focusing on the timing of events, the number of cells produced, and the type of cells at each stage. Answer: Oogenesis is the process of formation and development of the female gamete or ovum in animals. It begins during fetal development when oogonia are formed and undergo rapid mitosis. Before birth, oogonia enter Meiosis I, becoming primary oocytes. They are surrounded by follicular cells, forming primordial follicles. During each menstrual cycle, some of these follicles develop into mature (Graafian) follicles. At puberty, one primary oocyte completes Meiosis I, dividing into a larger secondary oocyte and a smaller polar body. The secondary oocyte proceeds to Meiosis II but stops at the metaphase stage until fertilization occurs. If fertilized, it completes Meiosis II, forming a mature ovum and another polar body. In summary, oogenesis results in one mature ovum and two or three polar bodies, which degenerate.