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An ovum (Latin: "egg", plural: ova) is the name for the haploid female reproductive cell, or gamete. Both animals and land plants (embryophytes) produce ova. At birth, a female has all of her eggs, and from puberty, she releases an egg once a month until none are left. This is called oogenesis. The ovum is fertilized inside the female body, and the embryo then develops inside the uterus, being fed by the mothers placenta.

The ovum is the largest cell in the human body. You can see it without a microscope. The human ovum is between 100 and 200 µm long. They are nevertheless much smaller than the cleidoic eggs laid externally by reptiles and birds, which is why they need a long period of internal development in the womb.[1][2][3][4]

Other mammals

The sexual cycle is quite different in other mammals, whose females are only receptive during their 'heat', which triggers the release of eggs from the ovary.

Plants

In many plants, ova are made inside archegonia through meiosis. The archegonium has a long 'neck' with the egg cell inside.

In flowering plants, the female gametes are made of only eight cells, called the embryo sac, inside the ovule. The cell closest to the opening of the embryo sac becomes the egg cell. The zygote then develops into an embryo inside the ovule. Cleidoic egg

Other websites

  • The Ovum, Gray's Anatomy of the Human Body, Yahoo! Education
  • Ovum, Online Medical Dictionary, CancerWEB, Newcastle University
  • Oogenesis, Dr. Uzwiak, New Jersey State University
  • Definition of Ovum, Biology-Online.org