Tuesday, January 12, 2010

Fascinating Facts: Eggs + Sperm

I have to confess that I have only gotten about half way though my book that I am re-reading up on IVF.

In doing so, I  would like to share some very fascinating facts about the egg and sperm.  Some of this is common knowledge, that even fertiles probably know about, but some are oh so very interesting.

Hello Egg, meet Sperm
  • About the size of a grain of sand, the human egg is the largest cell in the human body.
  • A woman develops all the eggs she will ever have at the fetal age of 12 weeks.
  • A female baby starts off with about 7 million eggs when she is in her mother's womb.
  • Her ovaries contain about 700,000 eggs by the time she reaches puberty
  • A woman uses about 300,000 of these eggs during the approximately 400 ovulations that occur during her reproductive life span.
  • In contrast to the egg, sperm are the smallest cells in the body.
  • The man's testicles generate a new complement of sperm every 100 days.
  • Eggs and sperm are called gametes until fertilization.
  • A fertilized egg is called a zygote until it begins to divide
  • From initial cell division through the first 8 weeks of gestation, it is known as an embryo.
  • From the 9th week of gestation until delivery, it is called a fetus.

Swim boys, swim!
  • Out of the millions of sperm ejaculated the vagina, only a few hundred  to a few thousand make successfully complete the journey to the waiting egg in the fallopian tube.
  • Fertilization process occurs near the middle of the fallopian tube, not in the uterus
  • The journey from the cervix to the fallopian tubes is about 4 inches.  For a cell the size of a sperm to travel this distance is equivalent to an adult human swimming the Pacific Ocean from Los Angeles to Tahiti - I was most fascinated by this.  
Can you imagine swimming from LA to Tahiti? Do you even know where Tahiti is?  It's in the middle of the Pacific Ocean!!  

That's approximately 4,000 miles or 6,500 km, or 8 hours flight time.



  1. Swim boys, swim is right! What an interesting way to think about it. Your eggs are in Tahiti. : )

  2. It's a miracle ANYONE gets pregnant! And yes Swim boys Swim is right!

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  4. Hey all, I can not repeat calculations. Sperm with size of 5 micron has to travel 4 inches.
    From my point of view 6' it is equivalent to 23 miles in my world. It is far but not Pacific Island. Regards Shiva Oslo

  5. Thanks Shiva, you saved me the trouble of pointing that one out!

    To be fair though, because of the water tension on the sperm's body it is more like trying to swim through 23 miles of treacle. This is one of the reasons that sperm "drill" rather than swim through the water.