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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.
Eventually, the oogonia will either degenerate or further differentiate into primary oocytes through asymmetric division. Asymmetric division is a process of mitosis in which one oogonium divides unequally to produce one daughter cell that will eventually become an oocyte through the process of oogenesis , and one daughter cell that is an ...
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 ...
The zona pellucida is a translucent matrix of cross-linked glycoprotein filaments that surrounds the mammalian oocyte and is 6.5–20 μm thick depending on the species. Its formation, which depends on a conserved zona pellucida-like (ZP) module that mediates the polymerization of egg coat components, [2] is critical to successful fertilization. [3]
In the ovaries, the developing egg cells (or oocytes) mature in the fluid-filled follicles. Typically, only one oocyte develops at a time, but others can also mature simultaneously. Follicles are composed of different types and number of cells according to the stage of their maturation, and their size is indicative of the stage of oocyte ...