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An oocyte (/ ˈ oʊ ə s aɪ t /, oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis ...
This is known as the primary oocyte. Human females are born with all the primary oocytes they will ever have. [10] Starting at puberty the process of meiosis can complete resulting in the secondary oocyte and the first polar body. [10] The secondary oocyte can later be fertilized with the male sperm.
In fact, a primary oocyte is, by its biological definition, a cell whose primary function is to divide by the process of meiosis. [16] However, although this process begins at prenatal age, it stops at prophase I. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, called the dictyate.
Folliculogenesis is continuous, meaning that at any time the ovary contains follicles in many stages of development. The majority of follicles die and never complete development. A few develop fully to produce a secondary oocyte which is released by rupture of the follicle in a process called ovulation.
Ovulation is the regular release of one oocyte from the ovary into the reproductive tract and is preceded by follicular growth. A few follicle cells are stimulated to grow but only one oocyte is ovulated. A primordial follicle consists of an epithelial layer of follicular granulosa cells enclosing an oocyte.
While undergoing mitotic expansion in the developing gonad, the male germline starts the re-methylation process by embryonic day 14.5. The sperm-specific methylation pattern is maintained during mitotic expansion. DNA methylation levels in primary oocytes before birth remain low, and re-methylation occurs after birth in the oocyte growth phase ...
In contrast with males, each of the original diploid germ cells or primary oocytes will form only one mature ovum, and three polar bodies which are not capable of fertilization. It has long been understood that in females, unlike males, all the primary oocytes ever found in a female will be created prior to birth, and that the final stages of ...
Oocyte (or ovum/egg) activation is a series of processes that occur in the oocyte during fertilization. Sperm entry causes calcium release into the oocyte. In mammals, this is caused by the introduction of phospholipase C isoform zeta (PLCζ) from the sperm cytoplasm. [1] Activation of the ovum includes the following events: