TY - CHAP M1 - Book, Section TI - Female Hypogonadism A1 - Bhagavath, Bala A1 - Conway, Gerard S. A1 - Carr, Bruce R. A2 - Sarafoglou, Kyriakie A2 - Hoffmann, Georg F. A2 - Roth, Karl S. Y1 - 2017 N1 - T2 - Pediatric Endocrinology and Inborn Errors of Metabolism, 2e AB - Between weeks 4 and 8 of gestation, undifferentiated germ cells migrate from the yolk sac to the genital ridges where they populate and allow the development of the ovaries by differentiating into oogonia. By week 6 of gestation mitosis of the oogonia begins, resulting in a population of over 3 million germ cells per ovary by 20 weeks.1 From 15 weeks, the oogonia begin to transform into oocytes by entering the first meiotic division which stops at prophase I. No further development occurs until menarche, when the first few go forward to complete meiosis I and proceed toward ovulation as a secondary oocyte. Meiosis II immediately follows meiosis I but is arrested at metaphase II and is only completed if fertilization occurs. Primordial follicles are formed from about 20 weeks gestation as granulosa cells move to surround each germ cell. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/16 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1140321044 ER -