Structure of ovum

Structure of ovum Human ovum is non-cleidoic, alecithal and microscopic in nature. (Fig. . (b)). Its cytoplasm called ooplasm contains a large nucleus called the germinal vesicle. The ovum is surrounded by three coverings namely an inner thin transparent vitelline membrane , middle thick zona pellucida and outer thick coat of follicular cells called corona radiata . Between the vitelline membrane and zona pellucida is a narrow perivitelline space. tail is the longest part of the sperm and is slender and tapering. It is formed of a central axial filament or axoneme and an outer protoplasmic sheath. The lashing movements of the tail push the sperm forward. The human male ejaculates about to million sperms during coitus. It is estimated that around percent of sperms must have normal shape of which at least per cent must show vigorous motility for normal fertility. The sperm is the smallest human cell and the ovum or egg is the largest human cell.