Slideshow: Early Events
Fertilization Begins
#363, Slide 2 of 24
| ||
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. |
