HL 1 Biology

11.4a Spermatogenesis

<<Spermatogenesis>>

  • production of sperm
  • location: testes (composed of narrow tubes, seminiferous tubules)
  • interstitial(Leydig) cells:  cells in the gaps between tubules
  • germinal epithelium: outer layer of cells, where process of sperm production begins
  • spermatozoa (sperm):  cells with developed tails
  • Sertoli cells: large nurse cells in the wall of tubule
  • Hormones involved in spermatogenesis: FSH, testosterone, LH
  • PROCESS:
    • cells in germinal epithelium divide by mitosis (to produce endless supply of diploid cells)
    • cells formed by mitosis displaced inwards + divide by mitosis once large
    • enlarged cells carry out 1st division of meiosis
    • 2 haploid cells carry out 2nd division of meiosis
    • 4 cells attach to a Sertoli cell (feeds them until become a sperm)
  • Structures helping production of semen: epididymis, seminal vesicles, prostate gland

<<Male & Female Gametes>>

  • Similarities: contain a haploid nucleus, have microtubules organizing centres 
  • Different: size, shape (round: tail), structure (complex: simple)
  • Spermatogenesis vs. Oogenesis:
  • similarities: both start with proliferation of cells by mitosis, involve cell growth before meiosis, involve 2 divisions of meiosis
  • differences: amount produced (millions sperms daily: 1 every 28 days), starting point (puberty: fetal development in females), amount produced per meiosis (4: 1)

================DBQ==========================================

Sperm Counts and Male Fertility (p.276)

1 a) In the summer, the production of sperms is lower than the amount produced in the winter. Yet the % of normal sperm remains the same for both country group. Also, the sperm production in the sumer in Finland has a relatively similar amount produced as the Danish men during the winter.

b) A reason for the difference could include the average temperature year long. In denmark, the temperature is always relatively higher than the temperature in Finland. Thus, we can see that in a warmer temperature, the production of sperms in males is lower than during a season with a cooler temperature.

2 a) Sperm production of men aged 20-45 is higher compared to those who are aged 18-20. The % normal sperm is also higher in men aged 20-45 than the men aged 18-20. Also unlike the large difference in sperm production between the  20-45 age group in Denmark and Finland, the men aged 18-20 in both countries are closely related.

b) Reasons for the differences in the production of sperms between the two age groups include their social position and amount of development. Since men aged 20-45 are more likely to have pregnant partners, more production of sperm is observed compared to the 18-20 year old men who are more likely to not have pregnant females. Also, the men in age group 18-20 may not be fully developed and completed puberty, compared to the men of 20-45.

3 a) The hypothesis that sperm production should be lower in Denmark than in Finland because of the rate of testicular cancer being high can be supported with the data. As the data shows the lower production in Denmark than Finland, possibly less healthy sperms are produced and a higher rate of testicular cancer is apparent. Possibly the humidity in Denmark affects the lower production of sperms and a higher rate of testicular cancer as well. Also, it is studied in Denmark, the chemicals in breast milk, like pesticides, were highly found in mothers which could have lead many Danish men to grow up to have a high rate of testicular cancer.

 

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One thought on “11.4a Spermatogenesis

  1. Grade 7 A consistent and thorough understanding of the required knowledge and skills, and the ability to apply them almost faultlessly in a wide variety of situations.

    DBQ: sperm counts and male fertility page 276

    1
    • (within a group) higher in winter than summer;
    • summer count in Finnish men (nearly) equal to
    winter count in Danish men;
    • no change in % normal sperm occurs with the change in seasons.

    2
    • younger men without pregnant partners have fewer defective sperm;
    • younger men have a lower sperm count;
    • less variability in younger men between the two national groups;

    3 Hypothesis supported by sperm count data.

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