6.6b Male Reproduction & IVF

12/03/2013 § Leave a comment

Reproduction starts when a male’s sperm fuses with a female’s egg. For humans, the gender of the embryo are determined by the tdf gene, which is usually found on the Y-chromosome, therefore the tdf gene would make the embryo a male. While estrogen and progesterone are the hormones that trigger the growth of female genitalia, testosterone is the hormone that triggers the development of male genitalia. It also fuels the sex drive in men.

Just for kicks, here are diagrams of the male and female reproductive system (because I hadn’t posted an image in the previous blog post).

Ladies first.

Gentlemen next.

Up next is the in vitro fertilization, or IVF, which is a method of fertilization that retrieves gametes, fertilizes them to create an embryo to be implanted in a surrogate mother’s uterus. This is for parents who cannot naturally conceive children for various reasons (whether the woman has blocked oviducts or the man has low or no sperm). Very simply put, the IVF involves first drugging the woman to put a stop to her menstrual cycle for the time being. Hormones are injected for her to develop many follicles. The man would provide sperm through his semen. Both the sperm and eggs developed by the male and female respectively are extracted and mixed together in a dish, and the healthiest embryo that results are implanted into the mother’s uterus. Of course, the mother would have to take a pregnancy test to make sure the embryo transfer worked.

We’ll be studying in vitro fertilization with more details in class, but the above paragraph is basically what happens for the male and female to conceive a child. It’s important to note that there are ethical issues associated with IVF – as always, some people are for IVF while others are against. An example of the arguments against IVF is that it’s an unnatural process, and humans have complete power in deciding which embryo (essentially a potential human being) gets to live and which doesn’t. An example of the arguments for IVF is that it bring happiness and a solution to unhappy parents who want children badly, and suffering due to genetic disease is greatly reduced because the embryo are screened before being transferred into the uterus.

 

Essay Questions

  1. Draw a labelled diagram of the adult female reproductive system. 4 marks
  2. Draw a labeled diagram of an adult male reproductive system. 6 marks
  3. Explain the processes involved in oogenesis in humans. 9 marks
  4. Draw the structure of a mature human egg. 4 marks
  5. Explain the role of hormones in the regulation of the menstrual cycle in human females. 8 marks
  6. Outline the levels of each of the hormones that control the menstrual cycle immediately before ovulation. 3 marks
  7. Explain the roles of LH and FSH in the menstrual cycle, including the timing of their secretion during the cycle. 6 marks
  8. Outline the roles of progesterone and estrogen in the human menstrual cycle. 6 marks
  9. Draw a labeled diagram of the structure of an ovary as seen using a light microscope. 5 marks
  10. Draw the structure of the human female reproductive system immediately before ovulation. (Only the ovaries, oviducts and uterus need to be shown.) 6 marks
  11. Draw a labelled diagram of a mature sperm. 5 marks
  12. Outline the process of spermatogenesis in humans. 5 marks
  13. Production of semen involves a series of processes, which in total take many weeks to carry out. Outline the processes involved in semen production from the start of sperm formation (spermatogenesis) to ejaculation. 8 marks
  14. Compare the process of spermatogenesis and oogenesis. 7 marks
  15. Discuss how, in humans, a larger number of sperms are produced than eggs. 4 marks
  16. Describe the process of fertilization in humans. 8 marks
  17. Describe the development of the early human embryo. 5 marks
  18. Outline the regulation of pregnancy by two named hormones. 4 marks
  19. Outline the role of human chorionic gonadotropin (HCG) in early pregnancy 2 marks
  20. Outline the way in which a pregnancy can be detected at a very early stage. 4 marks
  21. Compare the roles of LH and HCG in female reproduction. 2 marks
  22. State the role of the amniotic sac and the amniotic fluid. 2 marks
  23. Explain the function and structure of the placenta. 8 marks
  24. Outline the process of in vitro fertilization (IVF). 6 marks
  25. Discuss the ethical issues surrounding IVF. 6 marks
  26. Outline the role of positive feedback in the process of birth in humans. 4 marks

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