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Oogenesis (/ ˌ oʊ. ə ˈ dʒ ɛ n ɪ s ɪ s /) or ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. [1] It is developed from the primary oocyte by maturation.
Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle.In female humans ovulation typically occurs near the midpoint in the menstrual cycle and after the follicular phase.
An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries.It secretes hormones that influence stages of the menstrual cycle.At the time of puberty, women have approximately 200,000 to 300,000 follicles, [1] [2] each with the potential to release an egg cell (ovum) at ovulation for fertilization. [3]
The primary role of the follicle is oocyte support. From the whole pool of follicles a woman is born with, only 0.1% of them will rise ovulation, whereas 99.9% will break down (in a process called follicular atresia).
The determination of the dorsal side of the embryo occurs during oogenesis when the oocyte nucleus moves along microtubules from the posterior to the anterior-dorsal margin of the oocyte. The nucleus expresses a protein called Gurken which is secreted locally and thus only activates follicle cells in the dorsal region by interacting with the ...
The dictyate or dictyotene [1] is a prolonged resting phase in oogenesis.It occurs in the stage of meiotic prophase I [2] in ootidogenesis.It starts late in fetal life [2] and is terminated shortly before ovulation by the LH surge. [3]
In mammals, oogenesis is believed to be primarily prenatal. The existence of oogonial stem cells in mammals is controversial, [ 7 ] except for the finding of OSCs in two species of loris [ 8 ] [ 9 ] and three species of bat.
Parthenogenesis can occur without meiosis through mitotic oogenesis. This is called apomictic parthenogenesis. Mature egg cells are produced by mitotic divisions, and these cells directly develop into embryos. In flowering plants, cells of the gametophyte can undergo this process. The offspring produced by apomictic parthenogenesis are full ...