An Introduction to the Meiosis in the Ovary | BMS 360, Study notes of Biology

Download An Introduction to the Meiosis in the Ovary | BMS 360 and more Study notes Biology in PDF only on Docsity! 11 April Meiosis in the Ovary Oocytes are arrested in meiosis I at birth Follicle growth and maturation Oocyte completes meiosis I and ovulates Ovulated oocyte arrests in meiosis II Menopause – follicles no longer grow LH → theca cells → testosterone FSH → granulosa cells Testosterone → granulosa cells → estradiol Granulosa cells → inhibin → ↓ FSH Estradiol levels low Comes from growing follicles Negative feedback High levels of estradiol Come from dominant follicle Positive feedback to brain ↑ LH Two ovarian phases – follicular and luteal phase Follicular phase 1 – bleeding starts 7 – follicle becomes dominant 14 – ovulation Luteal phase Corpus luteum (CL) derived from left over cells Secretes progesterone, estradiol, low levels of inhibin Functions for ~11 days, then dies Continues function if pregnant Ovarian cycles – Follicular phase FSH stimulates follicle growth, estrogen levels are low (little negative feedback) Growing follicles secrete estrogen Dominant follicle secretes large amounts of estrogen High levels of estrogen causes LH surge Completion meiosis I Ovarian cycles – Luteal phase Ovulation occurs, formation of corpus luteum Corpus luteum secretes large amounts of estrogen and progesterone Negative feedback to brain; FSH, LH levels drop Corpus luteum degenerates; estrogen and progesterone levels drop. FSH and LH start to increase again → new cycle Ovarian-uterine interaction The rise and fall of estrogens and progesterone influence the endometrium in a cyclic manner, giving rise to menstrual cycle