10.7 The Reproductive Hormones

Transcription

1 10.7 The Reproductive Hormones December 10, 2013.

2 Website survey??

3 QUESTION: Who is more complicated: men or women?

4 The Female Reproductive System ovaries: produce gametes (eggs) produce estrogen (steroid hormones that stimulate and control the development and maintenance of the reproductive system) produce progesterone (prepares and maintains uterus for implantation of fertilized egg and growth/ development of the embryo)

5 The Female Reproductive System the process by which the ovaries produce and release eggs is called oogenesis and it controlled by hormones from the pituitary gland oogenesis is not ongoing ovulation: the monthly release of one or a few developing oocytes for possible fertilization if fertilization occurs, the zygote (fertilized egg) travels to the uterus if not, the unfertilized egg degenerates and disappears

6 The Female Reproductive System The Ovarian Cycle (changes in hormones and ovum) Day 0-13: release of GnRH (gonadotropin-releasing hormone) by the hypothalamus GnRH causes the pituitary to release FSH (folliclestimulating hormone) and LH (luteinizing hormone) FSH stimulates oocyte to start to mature maturing oocytes become surrounded by cells that form a follicle FSH and LH stimulate follicle cells to release estrogen

7 Menstrual Cycle

8 The Female Reproductive System The Ovarian Cycle (changes in hormones and ovum) Day 14: high estrogen increases the release of GnRH which causes the pituitary to release a burst of FSH and LH ovulation occurs: egg is released from the follicle cells

9 Menstrual Cycle

10 The Female Reproductive System The Ovarian Cycle (changes in hormones and ovum) Day 15-28: LH causes the follicle cells to form a mass of cells called the corpus luteum - this prepares the uterus to receive a fertilized egg the corpus luteum acts like a gland secretes estrogen secretes progesterone: stimulates growth of uterine b and inhibits contractions of the uterus and inhibits the release of GnRH (and therefore FSH and LH) secretes inhibin: inhibit secretion of FSH if fertilization does not occur, the corpus luteum gradually shrinks - this inhibits secretion of estrogen, progesterone and inhibin and menstruation begins

11 Menstrual Cycle

12 The Female Reproductive System The Menstrual Cycle (changes in the uterus only) Day 0-5: everything needed for egg implantation in the uterus (called the endometrium) is released from the body Day 6-14: new endometrium grows and thickens, and oocytes develop leading to ovulation Day 15-28: endometrium continues to grow no fertilization? endometrium breaks down and contractions begin

13 Menstrual Cycle Day 0-5

14 Menstrual Cycle Day 6-14

15 Menstrual Cycle Day 14

16 Menstrual Cycle Day 15-28

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18 Fertilization and Pregnancy fallopian tube/ oviduct fertilization usually occurs here uterus ovary ovary

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20 Fertilization and Pregnancy

21 Fertilization and Pregnancy after the nuclei of the sperm and egg fuse, the cell is called a zygote mitotic divisions begin and the embryo develops after a week, the embryo implants in the uterus and secretes human chorionic gonadotropin (hcg) - this keeps the corpus luteum from breaking down and suppresses the mother s immune system excess hcg is excreted in urine (which is the basis for pregnancy tests) the corpus luteum maintains the uterine lining and prevents menstruation

22 Male Hormones testes secrete androgens (hormones that control the development and maintenance of the male reproductive system) i.e. testosterone: stimulates puberty synthesis and secretion of testosterone is controlled by the release of LH from the pituitary release of LH is controlled by GnRH in the hypothalamus

23 Male Hormones spermatogenesis: sperm cells are produced in the testes from precursor cells called spermatogonia sperm constantly produced: 130 million a day!! sperm go from the seminiferous tubules to the epididymis and then the vas deferans hypothalamus secretes GnRH which stimulates the pituitary to secrete LH and FSH LH and FSH acts on the testes to stimulate the release of testosterone and therefore sperm production