About sixty hours after fertilization, approximately sixteen cells have formed to what is called a morula, still enclosed by the zona pellucida; three days after fertilization, the morula enters the uterus.
2
Conn's syndrome is also very rare, caused by a benign adenoma or hyperplasia of the zona glomerulosa producing excess aldosterone.
3
For fertilization to occur, a sperm must penetrate the tough outer membrane of the egg called the zona pellucida.
4
The egg is surrounded by a special coat called the zona pellucida.
5
The zona granulosa cells begin to secrete progesterone (granulosa lutein cells ).
6
The zona pellucida disappears and the morula becomes a blastocyst.
7
When one sperm successfully binds with the zona pellucida, a series of chemical reactions occurs to allow only that sperm to penetrate.