Organismal Development Part 4 Female Animals

Female Reproductive Anatomy Oviduct Ovaries Follicles Corpus luteum Uterine wall Uterus Endometrium Cervix Vagina

Oogenesis in the ovaries Ovary Primary germ cell in embryo Differentiation Oogonium in ovary Oogonium Mitotic division Primary oocyte within follicle Primary oocyte Completion of meiosis I and onset of meiosis II Growing follicle Secondary oocyte First polar body Ovulation Entry of sperm triggers completion of meiosis II Mature follicle Ruptured follicle Second polar body Ovum Ovulated secondary oocyte Corpus luteum Degen- erating corpus luteum

Female Reproductive Cycle in Humans Control by hypothalamus Inhibited by combination of estrogen and progesterone Hypothalamus Stimulated by high levels of estrogen GnRH Anterior pituitary Inhibited by low levels of estrogen FSH LH Pituitary gonadotropins in blood LH FSH FSH and LH stimulate follicle to grow LH surge triggers ovulation Ovarian cycle Corpus luteum Degenerating corpus luteum Growing follicle Mature follicle Follicular phase Ovulation Luteal phase Estrogen secreted by growing follicle in increasing amounts Progesterone and estrogen secreted by corpus luteum Ovarian hormones in blood Peak causes LH surge Estrogen Progesterone Estrogen level very low Progesterone and estro- gen promote thickening of endometrium Uterine (menstrual) cycle Endometrium Menstrual flow phase Proliferative phase Secretory phase Days 5 10 14 15 20 25 28

Fertilization and Implantation if pregnancy occurs Cleavage starts Cleavage continues Ovary Fertilization occurs The blastocyst implants Uterus Ovulation Endometrium From ovulation to implantation