When do mitotic divisions of oogonia leading to primary oocytes primarily occur in human females?

Mitotic divisions of oogonia, which are the initial germ cells in the female reproductive system, primarily occur during fetal development in human females. This process begins in the ovaries while the female fetus is still developing. The oogonia undergo mitosis to produce millions of germ cells, which subsequently differentiate into primary oocytes.

By the time of birth, a female has a finite number of primary oocytes that have entered prophase of meiosis I, and these remain arrested in this stage until ovulation occurs later in life. After birth, no new oogonia are formed, and the primary oocytes do not undergo further mitotic divisions; instead, they will be periodically chosen to complete meiotic division during the menstrual cycle after puberty.

This developmental timeline is crucial for understanding female reproductive biology, as it lays the foundation for the number and quality of oocytes available throughout a woman’s reproductive years.