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Concept
Folliculogenesis
Summary
Although the process is similar in many animals, this article will deal exclusively with human folliculogenesis.
In biology, folliculogenesis is the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte. 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 that previously recruited some follicles to mature. This depletion in follicle supply signals the beginning of menopause.
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). From birth, the ovaries of the human female contain a number of immature, primordial follicles. These follicles each contain a similarly immature primary oocyte. At puberty, clutches of follicles begin folliculogenesis, entering a growth pattern that ends in ovulation (the process where the oocyte leaves the follicle) or in atresia (death of the follicle's granulosa cells).
During follicular development, primordial follicles undergo a series of critical changes in character, both histologically and hormonally. First they change into primary follicles and later into secondary follicles. The follicles then transition to tertiary, or antral, follicles. At this stage in development, they become dependent on hormones, particularly FSH which causes a substantial increase in their growth rate. The late tertiary or pre-ovulatory follicle ruptures and discharges the oocyte (that has become a secondary oocyte), ending folliculogenesis.
Follicle ‘selection’ is the process by which a single ‘dominant’ follicle is chosen from the recruited cohort or wave for preferential growth.
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Ontological neighbourhood
Related courses (1)
BIO-321: Morphology II
Ce cours permet aux étudiants ayant suivi Morphologie I de réviser et d'approfondir leurs connaissances par l'étude de l'anatomie radiologique et du développement. L'origine de malformations fréquente
Related publications (26)
Related people (5)
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Activin and inhibin
Activin and inhibin are two closely related protein complexes that have almost directly opposite biological effects. Identified in 1986, activin enhances FSH biosynthesis and secretion, and participates in the regulation of the menstrual cycle. Many other functions have been found to be exerted by activin, including roles in cell proliferation, differentiation, apoptosis, metabolism, homeostasis, immune response, wound repair, and endocrine function. Conversely, inhibin downregulates FSH synthesis and inhibits FSH secretion.
Hypothalamic–pituitary–gonadal axis
The hypothalamic–pituitary–gonadal axis (HPG axis, also known as the hypothalamic–pituitary–ovarian/testicular axis) refers to the hypothalamus, pituitary gland, and gonadal glands as if these individual endocrine glands were a single entity. Because these glands often act in concert, physiologists and endocrinologists find it convenient and descriptive to speak of them as a single system. The HPG axis plays a critical part in the development and regulation of a number of the body's systems, such as the reproductive and immune systems.
Puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed.