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First stages of segmentation of a mammalian embryo. Semidiagrammatic. z.p. Zona pellucida. p.gl. Polar bodies. a. Two-cell stage. b. Four-cell stage. c. Eight-cell stage. d, e. Morula stage. A polar body is a small haploid cell that is formed at the same time as an egg cell during oogenesis, but generally does not have the ability to be ...
Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum Oocyte meiosis, important to all animal life cycles yet unlike all other instances of animal cell division, occurs completely without the aid of spindle ...
Each primary oocyte divides twice in meiosis, unequally in each case. The first division produces a daughter cell, and a much smaller polar body which may or may not undergo a second division. In meiosis II, division of the daughter cell produces a second polar body, and a single haploid cell, which enlarges to become an ovum. Therefore, in ...
Thus, it has only one of each pair of homologous chromosomes. In other words, it is haploid. However, each chromosome still has two chromatids, making a total of 46 chromatids (1N but 2C). The secondary oocyte continues the second stage of meiosis (meiosis II), and the daughter cells are one ootid and one polar body.
The oocyte completes its second meiotic division. This results in a mature haploid ovum and the release of a polar body. [22] The nucleus of the oocyte is called a pronucleus in this process, to distinguish it from the nuclei that are the result of fertilization. Drawing of an ovum
The LH surge that occurs during ovulation triggers the release of the oocyte and its cumulus oophorus from the ovary and into the fallopian tube and triggers the oocyte to divide and enter metaphase of meiosis II (46 or 2n chromosome) and extrude its first polar body. The oocyte will only continue through meiosis and extrude its second polar ...
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The meiotic division I produces 2 cells differing in size: a small polar body and a large secondary oocyte. The secondary oocyte undergoes meiotic division II and that results in the formation of a second small polar body and a large mature egg, both being haploid cells. The polar bodies degenerate. [12]