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Diagram showing the reduction in number of the chromosomes in the process of maturation of the ovum; the process is known as meiosis Main article: Oogenesis The formation of an oocyte is called oocytogenesis, which is a part of oogenesis. [ 1 ]
Oogenesis starts with the process of developing primary oocytes, which occurs via the transformation of oogonia into primary oocytes, a process called oocytogenesis. [11] From one single oogonium, only one mature oocyte will rise, with 3 other cells called polar bodies.
In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
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Animals, including mammals, produce gametes (sperm and egg) through meiosis in gonads (testicles in males and ovaries in females). Sperm are produced by the process of spermatogenesis and eggs are produced by oogenesis. These processes are outlined in the article gametogenesis.
Drawing of the head of a four-week-old human embryo. From Gray's Anatomy. Embryo drawing is the illustration of embryos in their developmental sequence. In plants and animals, an embryo develops from a zygote, the single cell that results when an egg and sperm fuse during fertilization. In animals, the zygote divides repeatedly to form a ball ...
The following outline is provided as an overview of and topical guide to zoology: . Zoology – study of animals.Zoology, or "animal biology", is the branch of biology that relates to the animal kingdom, including the identification, structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems.
Oocytogenesis : third trimester primary Oocyte: diploid/46: 4C: Ootidogenesis (meiosis 1) (Folliculogenesis) -- polar body separated: Dictyate in prophase I until ovulation secondary Oocyte: haploid/23: 2C: Ootidogenesis (meiosis 2) -- polar body separated: Halted in metaphase II until fertilization Ootid: haploid/23: 1C: Maturation: Minutes ...