13/03/2013 § 2 Comments
Genesis is the creation of something. Soooo, if we smash “sperm” and a few more letters into the word “genesis,” then we get spermatogenesis, which is the production of sperm. This production occurs in the seminiferous tubules of the testes, which are a mass of narrow tubes. Between the tubules are interstitial cells, which make up gaps called interstices. The outer layer of cells that makes up the seminiferous tubules is called the germinal epithelium. Sperm in production are contained within the germinal epithelium and the ones closest to the mature stage are closer to the fluid-filled centers. Sperm cells that have developed tails are called spermatozoa, but we know them as sperm. Then, there are brilliantly altruistic nurse cells called Sertoli cells that feed the sperm as they develop.
The hormones involved in the production of sperm cells are: FSH, testosterone, and LH. Note that FSH and LH are also used in the production of egg cells. Semen is also produced with the sperm for various reasons. The semen contains nutrients for the sperm like fructose as well as mineral ions (making it alkaline) to protect them from the vagina’s acidic conditions.
- Draw a labelled diagram of the adult female reproductive system. 4 marks
- Draw a labeled diagram of an adult male reproductive system. 6 marks
- Explain the processes involved in oogenesis in humans. 9 marks
- Draw the structure of a mature human egg. 4 marks
- Explain the role of hormones in the regulation of the menstrual cycle in human females. 8 marks
- Outline the levels of each of the hormones that control the menstrual cycle immediately before ovulation. 3 marks
- Explain the roles of LH and FSH in the menstrual cycle, including the timing of their secretion during the cycle. 6 marks
- Outline the roles of progesterone and estrogen in the human menstrual cycle. 6 marks
- Draw a labeled diagram of the structure of an ovary as seen using a light microscope. 5 marks
- Draw the structure of the human female reproductive system immediately before ovulation. (Only the ovaries, oviducts and uterus need to be shown.) 6 marks
- Draw a labelled diagram of a mature sperm. 5 marks
- Outline the process of spermatogenesis in humans. 5 marks
- 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
- Compare the process of spermatogenesis and oogenesis. 7 marks
- Discuss how, in humans, a larger number of sperms are produced than eggs. 4 marks
- Describe the process of fertilization in humans. 8 marks
- Describe the development of the early human embryo. 5 marks
- Outline the regulation of pregnancy by two named hormones. 4 marks
- Outline the role of human chorionic gonadotropin (HCG) in early pregnancy 2 marks
- Outline the way in which a pregnancy can be detected at a very early stage. 4 marks
- Compare the roles of LH and HCG in female reproduction. 2 marks
- State the role of the amniotic sac and the amniotic fluid. 2 marks
- Explain the function and structure of the placenta. 8 marks
- Outline the process of in vitro fertilization (IVF). 6 marks
- Discuss the ethical issues surrounding IVF. 6 marks
- Outline the role of positive feedback in the process of birth in humans. 4 marks
DATA BASED QUESTIONS
Page 276, sperm counts and male fertility
- a) Compare sperm production in summer and in winter. —> The sperm count for both Denmark and Finland is larger during the Winter as opposed to the sperm count in the Summer. The percentage of normal sperm is the same all throughout the year (52% all year round for Finland and 48% all year round for Denmark).
- b) Suggest reasons for the difference. —> Though Denmark and Finland are both in Europe and have about the same climate, the culture and diet in both countries could very likely be different.
- a) Compare the sperm production of men aged 20-45 with pregnant partners, with the sperm production of men aged 18-20. —> The sperm count for men with pregnant partners (ages 20 – 45) is larger so than men aged 18 – 20. In Denmark, the younger men produce only 41 million sperm per ml of semen while the older men with pregnant partners produce sperm from 69 – 98 million sperm per ml of semen throughout the year. In Finland, the younger men produce only 54 million sperm per ml of semen compared to the older men with pregnant partners who produce sperm from 93 – 132 million sperm per ml of semen throughout the year.
- b) Suggest two reasons for the difference. —> The younger men who are reporting for military service probably have more on their minds than just sex, but their diets are different than the normal men with pregnant partners. Also, the men with pregnant partners have a more active sex drive. Maybe. I DON’T KNOW, DON’T ASK ME.
3. Evaluate the hypothesis that sperm production should be lower in Denmark than in Finland because the rate of testicular cancer is higher.
The data given in Table 4 shows that the men in Denmark DO have a lower sperm count than the men in Finland (whether it be the younger men reporting for military service, or the older men with pregnant partners). This makes sense because if men have testicular cancer, then the tumor that grows on the testes will limit the efficiency of the reproductive system, resulting in a lower production of sperm cells.