STRUCTURE OF OVUM

 

Structure Of Ovum: After the process of oogenesis -  an egg or the ovum is formed . Egg is released during the ovulation phase.

 

 Ovum is rounded, non motile cell. It is almost  free of  yolk and is called as alecithal. It has abundant cytoplasm , called ooplasm. It has a nucleus called as Germinal vesicle and there is the prominent occurrence of nucleolus. The nucleolus is surrounded by plasma membrane called  oolemma.  

There are no centrioles in the ovum. The ovum shows polarity. Its side which extrudes polar bodies called animal pole. The opposite side is called vegetal  pole. The ovum is enclosed by two additional egg coats: inner thin, transparent , non cellular zona pellucid and outer thick corona radiate.  

Zona  Pellucida is secreted by ovum itself and is called primary egg membrane. It is formed of three different glycol proteins. The corona radiate is formed of radically elongated follicular cells.

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