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Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that occurs in part during the menstrual cycle. Contrary to male spermatogenesis , which can last indefinitely, folliculogenesis ends when the remaining follicles in the ovaries are incapable of responding to the hormonal cues ...
In the absence of the Y chromosome, the gonads will differentiate into ovaries. As the ovaries differentiate, ingrowths called cortical cords develop. This is where the primordial germ cells collect. [3] [4] During the 6th to 8th week of female (XX) embryonic development, the primordial germ cells grow and begin to differentiate into oogonia.
A primordial follicle consists of an epithelial layer of follicular granulosa cells enclosing an oocyte. The pituitary gland secrete follicle-stimulating hormones (FSHs) that stimulate follicular growth and oocyte maturation. The thecal cells around each follicle secrete estrogen. This hormone stimulates the production of FSH receptors on the ...
In this way, the rudiments of the ovarian follicles are formed. During oogenesis, the oogonia become primary oocytes. Oocytes (immature ova) residing in the primordial follicle of the ovary are in a non-growing prophase arrested state, but have the capacity to undergo highly efficient homologous recombinational repair of DNA damages including ...
Over time, many studies have been conducted with the aim to optimize the characteristics of ovarian tissue culture systems and to better support the three main phases: 1) activation of primordial follicles; 2) isolation and culture of growing preantral follicles; 3) removal from the follicle environment and maturation of oocyte cumulus complexes.
CCs primarily support growth and development of the oocyte whereas MGCs primarily serve an endocrine function and support the growth of the follicle. Cumulus cells aid in oocyte development and show higher expression of SLC38A3, a transporter for amino acids, and Aldoa, Eno1, Ldh1, Pfkp, Pkm2, and Tpi1, enzymes responsible for glycolysis. [ 7 ]
Ovarian follicle activation can be defined as primordial follicles in the ovary moving from a quiescent (inactive) to a growing phase. The primordial follicle in the ovary is what makes up the “pool” of follicles that will be induced to enter growth and developmental changes that change them into pre-ovulatory follicles, ready to be released during ovulation.
All of the oogonia and many primary oocytes die before birth. After puberty in primates, small groups of oocytes and follicles prepare for ovulation by advancing to metaphase II. Only after fertilization is meiosis completed. Meiosis is asymmetric producing polar bodies and oocytes with large amounts of material for embryonic development.