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Related Concept Videos

Oogenesis02:07

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
Nondisjunction01:29

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.
Nondisjunction01:21

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers.  Nondisjunction is common during anaphase I or anaphase II of meiosis.  Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...
Ovarian Cycle01:27

Ovarian Cycle

The menstrual cycle includes a critical component known as the ovarian cycle, which undergoes two main phases each month—the follicular phase and the luteal phase. The follicular phase is variable and averaging around 14 days. Ovulation, triggered by a surge in luteinizing hormone (LH), marks the transition between the two phases. The second phase, the luteal phase, is relatively consistent, lasting approximately 14 days, and is marked by the activity of the corpus luteum. While a cycle length...
Oogenesis01:22

Oogenesis

Oogenesis,  the process of developing egg cells (female gametes), occurs within the ovaries and is fundamental to female fertility. This sequence begins during fetal development when diploid oogonia in the developing ovaries undergo mitotic divisions to produce primary oocytes. By birth, these primary oocytes enter prophase I of meiosis but become arrested in this stage, remaining suspended until puberty.
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...
Hormonal Control of the Ovarian Cycle01:30

Hormonal Control of the Ovarian Cycle

The ovarian cycle is meticulously regulated by the hypothalamic-pituitary-gonadal axis. This cycle orchestrates the release of a mature oocyte, essential for reproduction.
Before puberty, the hypothalamus releases GnRH in a low frequency, low amplitude pulsatile manner. This along with the immature hypothalamic-pituitary-gonadal axis activity, results in low estrogen levels and the absence of a fully functional ovarian cycle.  At puberty, GnRH secretion increases in both frequency and...

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Related Experiment Video

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Human Egg Maturity Assessment and Its Clinical Application
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Human Egg Maturity Assessment and Its Clinical Application

Published on: August 19, 2019

An eleven-year cycle in human births.

W Randall1

  • 1Department of Psychology, University of Iowa, Iowa City 52242.

International Journal of Biometeorology
|June 1, 1991
PubMed
Summary

Human conception rates show a reliable connection to the sun's 11-year cycle. This study confirms a direct relationship between the sunspot cycle and birth data from the 20th century.

Area of Science:

  • * Environmental Science
  • * Human Demographics
  • * Solar Physics

Background:

  • * The sun exhibits an approximately 11-year endogenous cycle.
  • * Previous research suggests potential links between solar cycles and human biological processes.
  • * Understanding these connections may reveal environmental influences on human reproduction.

Purpose of the Study:

  • * To investigate the correlation between the solar cycle and human conception rates.
  • * To analyze birth data for evidence of an 11-year periodicity.
  • * To explore potential mediating factors in the observed relationship.

Main Methods:

  • * Utilized time series analysis, including periodograms and periodic regression.
  • * Analyzed 20th-century birth data from the United States (1909-1985).

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  • * Analyzed 20th-century birth data from New Zealand (1909-1985).

    • Main Results:

    • * An approximate 11-year periodicity was identified in birth data from both countries.
    • * A reliable and direct statistical relationship was found between human conceptions and the 11-year sunspot cycle.
    • * The findings support a link between solar activity and human reproductive patterns.

    Conclusions:

    • * The 11-year solar cycle appears to be a significant factor influencing human conception.
    • * Geomagnetic disturbances are discussed as a potential mediating mechanism.
    • * Further research is warranted to fully elucidate the environmental and biological pathways involved.