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The Endowment for Human Development
The Endowment for Human Development
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Fertilization Begins

Fertilization Begins [Click for next image]
From The Biology of Prenatal Development.Buy Now

Note:

Fertilization begins when a single spermatozoon penetrates the zona pellucida, which surrounds the oocyte. This event triggers a reaction called the zona reaction, which dramatically alters the outer membrane and prevents the entry of any additional spermatozoa into the oocyte.

Label Key:

1. principal piece of spermatozoon
2. zona pellucida
3. midpiece
4. neck
5. postacromial region
6. acrosomal cap
All ages referenced to fertilization, not last menstrual period.
Ready for Birth and Beyond
Ready for Birth and Beyond
The Calm Before the Storm
The Calm Before the Storm
Fertilization Begins
Fertilization Begins
Chromosomes
Chromosomes
DNA Structure
DNA Structure
A Human Cell
A Human Cell
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