10.7 the reproductive - koning sciencekoningscience.weebly.com/.../10.7_reproductive.pdf · male...

10.7 The Reproductive Hormones December 10, 2013.

Tuesday, 10 December, 13

Website survey??


QUESTION:

Who is more complicated: men or women?


• 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


• 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



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 Ovarian Cycle (changes in hormones and ovum)


Menstrual Cycle


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




Menstrual Cycle


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




Menstrual Cycle



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


Day 0-5Menstrual

Cycle


Day 6-14Menstrual

Cycle


Day 14Menstrual

Cycle


Day 15-28Menstrual

Cycle


Fertilization and Pregnancy

ovary

uterus

ovary

fallopian tube/oviduct

fertilization usually occurs

here



• 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


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


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


10.7 the reproductive - koning sciencekoningscience.weebly.com/.../10.7_reproductive.pdf · male...

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