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10.7 The Reproductive Hormones December 10, 2013.
Tuesday, 10 December, 13
Website survey??
Tuesday, 10 December, 13
QUESTION:
Who is more complicated: men or women?
Tuesday, 10 December, 13
• 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)
The Female Reproductive System
Tuesday, 10 December, 13
• 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
The Female Reproductive System
Tuesday, 10 December, 13
Day 0-13: release of GnRH (gonadotropin-releasing hormone) by the hypothalamus
•GnRH causes the pituitary to release FSH (follicle-stimulating 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
The Female Reproductive System
The Ovarian Cycle (changes in hormones and ovum)
Tuesday, 10 December, 13
Menstrual Cycle
Tuesday, 10 December, 13
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
The Female Reproductive System
The Ovarian Cycle (changes in hormones and ovum)
Tuesday, 10 December, 13
Menstrual Cycle
Tuesday, 10 December, 13
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
The Female Reproductive System
The Ovarian Cycle (changes in hormones and ovum)
Tuesday, 10 December, 13
Menstrual Cycle
Tuesday, 10 December, 13
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
Tuesday, 10 December, 13
Day 0-5Menstrual
Cycle
Tuesday, 10 December, 13
Day 6-14Menstrual
Cycle
Tuesday, 10 December, 13
Day 14Menstrual
Cycle
Tuesday, 10 December, 13
Day 15-28Menstrual
Cycle
Tuesday, 10 December, 13
Tuesday, 10 December, 13
Fertilization and Pregnancy
ovary
uterus
ovary
fallopian tube/oviduct
fertilization usually occurs
here
Tuesday, 10 December, 13
Tuesday, 10 December, 13
Fertilization and Pregnancy
Tuesday, 10 December, 13
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
Tuesday, 10 December, 13
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
Tuesday, 10 December, 13
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
Tuesday, 10 December, 13