Corona radiata (embryology)
| Corona radiata (embryology) | |
|---|---|
 Human ovum examined fresh in the liquor folliculi. The zona pellucida is seen as a thick clear girdle surrounded by the cells of the corona radiata. The egg itself shows a central granular deutoplasmic area and a peripheral clear layer, and encloses the germinal vesicle, in which is seen the germinal spot. | |
| Anatomical terminology |
- For the structure in neuroanatomy, see Corona radiata.
The corona radiata surround an ovum or unfertilized egg cell, and consist of two or three strata (layers) of follicular cells. They are attached to the outer protective layer of the ovum, the zona pellucida, and their main purpose in many animals is to supply vital proteins to the cell.[citation needed] They appear at ovulation, but may disappear eventually after fertilization.
The corona radiata are layers of follicle cells, that protect the secondary oocyte as it passes through the ruptured follicular wall, on its way to the infundibulum of the uterine (AKA fallopian) tubes. In order for fertalization to occur, the sperm must break through this layer of follicular cells by secreting the enzyme hyaluronidase. It takes the secretions of dozens of sperm to weaken the layer enough for one sperm to penetrate.
External links
- Image at Berkeley
- Histology image: 18404loa – Histology Learning System at Boston University
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