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Lecture 12

BI459 Lecture 12: BI459 Exam Review - Lecture 12

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Wilfrid Laurier University

Lecture 12: Reproduction II Female Reproductive System - Components o Ovaries o Reproductive Tract:  Uterine/fallopian tubes (oviduct)  Uterus  Vagina o External Genitalia  Labia  Clitoris o Accessory organs  Mammary gland  Marsupial pouch - Functions: o Production of female gametes (ova) o Endocrine Production of estrogen, progesterone o ETC… Hormones involved in Sexual Differentiation of Female Genital Tract - Absence of T causes mesopnephric ducts to regress - Absence of AMH (MIS) action allows paramesonephric ducts to differentiate Oogenesis & Follicular Development in Ovary - Follicle = the EGG + Surrounding cells o Thecal cells + granulosa cells - Zona Pellucida = noncellular membrane surrounding egg Growth & Maturation of Follicles Lecture 12: Reproduction II - Early in the cycle, as many as 50 follicles begin to develop but only one follicle normally matures to the point of ovulation - 2 main stages: 1. (early) gonadotropin (FSH)-independent growth 2. gonadotroping (FSH)-dependent growth o minimm “tonic” level of gonadotropins required o ONE dominant follicle becomes “gonadotropin independent” ad inhibits the growth of rest of follicles (still gonadotropin-dependent)  atresia - Secretes large amounts of inhibin  suppresses the secretion of FSH - Secretes substance that act directly on rest of follicles 1. FSH stimulates granulosa cells to produce small amounts of aromatase: T  E 2. LH stimulates theca cells to produce androgens (e.g. testosterone) - Effects of estrogen: o Up-regulation of LH receptors on granulosa cells  able to respond to LH surge  resumption of meiosis + ovulation Hormonal Control of Ovarian Cycle - Hierarchical control: o Hypothalamus (GnRH)  A. hypophysis (FSH/LH)  ovary (E+P)  other reproductive organs 1. Folicular Phase = Estrogen Release o Priming some tissues to respond later to progesterone o Increased responsiveness of the anterior pituitary to GnRH and a surge in the hypothalamic secretion of GnRH (positive feedback) o Preovulatory surge of LH (and FSH) which lead to ovulation o Inhibin produced by granulosa inhibits FSH secretion 2. Luteal Phase = Secretion of P (and some E) 3. Regression of Corpus Luteum = reduction in P and E Secretion Uterus (corpus) - Endometrium o Epithelium (secretory + ciliated cells) + stroma + uterine glands + spiral arteries o 2 endometrial zones; functional (sloughed off) & basal (regenerative) - Mymetrium o Increase in size during pregnancy Hormones and Changes during Uterine Cycle - Cyclic changes in endometrium (28-30day cycle in human females) - Phases: 1. Proliferative (Follicular) Stroma thickens, glands, elongate, spiral arteries grow 2. Secretory (Luteal) Glands accumulate glycogen and other secretory products; spiral arteries grow faster 3. Menstrual (degeneration of corpus luteum) Infiltration of stroma with leukocytes, breakdown of the spiral arteries  ischemia  hemorrhage  menstruation Hormone Levels during Ovarian & Uterine Cycles Lecture 12: Reproduction II - Follicular Phase: o Raising levels of estrogen o Inhibin inhibits the secretion of FSH o Surge in the hypothalamic secretion of GnRH and a preovulatory surge of LH (and FSH)
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