| Ovarian follicle | |
|---|---|
 |
|
| Human ovarian follicle | |
| Latin | folliculi ovarici primarii, folliculi ovarici vesiculosi |
| Gray's | subject #266 1256 |
| Precursor | cortical cords |
| MeSH | Ovarian+Follicle |
| Dorlands/Elsevier | f_11/12372180 |
Ovarian follicle is the basic unit of female reproductive biology and is composed of a roughly spherical aggregations of cells found in the ovary. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Gray's Anatomy the Respiratory apparatus ( Apparatus Respiratorius Respiratory system Respiratory apparatus Embryology (from Greek grc ἔμβρυον embryon, "unborn embryo" and grc -λογία -logia) is the study of the development In Embryology, cortical cords (also called secondary cords) are structures that develop from Sex cords in the female Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum. They contain a single oocyte (aka ovum or egg). An oocyte, ovocyte, or rarely ocyte, is a female Gametocyte or Germ cell involved in reproduction. An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single competent oocyte. Note This article deals primarily with Human ovulation nonhuman Animal ovulation is touched on briefly at the conclusion
Contents |
Structure
The cells of the ovarian follicle are the oocyte, granulosa cells and the cells of the internal and external theca layers.
Oocyte
The oocyte in a follicle is in the stage of a primary oocyte. The nucleus of such an oocyte is called a germinal vesicle[1] (see picture). An oocyte, ovocyte, or rarely ocyte, is a female Gametocyte or Germ cell involved in reproduction.
Granulosa
The oocyte is surrounded by a glycoprotein layer, the zona striata, or zona pellucida. The zona pellucida (or zona striata in older texts is a Glycoprotein membrane surrounding the Plasma membrane of an Oocyte. This, in turn, is swaddled in a layer of granulosa cells. A granulosa cell is a Somatic cell found closely associated with the developing female Gamete (called an Oocyte or egg In early tertiary follicles, the granulosa cells connecting the oocyte to the rest of the granulosa cells (membrana granulosa are the discus proligerus or cumulus oophorus. At one part of the mature follicle the cells of the Membrana granulosa are collected into a mass which projects into the cavity of the follicle
Theca
The granulosa cells, in turn, are enclosed in a thin layer of extracellular matrix – the follicular basement membrane or basal lamina (fibro-vascular coat in picture). In Biology, the extracellular matrix ( ECM) is the Extracellular part of animal tissue that usually provides structural support to the cells Outside the basal lamina, the layers theca interna and theca externa are found. The theca folliculi comprise a layer of the Ovarian follicles They appear as the follicles become Tertiary follicles The theca are divided into two layers the The theca folliculi comprise a layer of the Ovarian follicles They appear as the follicles become Tertiary follicles The theca are divided into two layers the
Development
Primordial follicles are indiscernible to the naked eye. In Biology, folliculogenesis is the maturation of the Ovarian follicle, a densely-packed shell of Somatic cells that contains an immature Oocyte However, they develop to primary, secondary and finally mature vesicular follicles. Mature vesicular follicles are sometimes called Graafian follicles (after Regnier de Graaf). Regnier de Graaf ( July 30, 1641 – August 17, 1673) was a Dutch Physician and anatomist who made key discoveries
In humans, oocytes are established in the ovary before birth, and may lay dormant awaiting initiation for up to 50 years [2].
After rupturing, the follicle is turned into a corpus luteum. The corpus luteum ( Latin for "yellow body" (plural corpora lutea) is a temporary Endocrine structure in mammals involved in production of
Development of oocytes in ovarian follicles
In a larger perspective, the whole folliculogenesis from primordial to preovulatory follicle is located in the stage of meiosis I of ootidogenesis in oogenesis. Oogenesis or rarely oögenesis is the creation of an Ovum (egg cell Oogenesis or rarely oögenesis is the creation of an Ovum (egg cell
The embryonic development doesn't differ from the male one, but follows the common path before gametogenesis. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular Gametogenesis is a process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid Gametes Depending on the Biological Once gametogonia enter the gonadal ridge, however, they attempt to associate with these somatic cells. In Embryology, the gonadal ridge (or genital ridge) is the precursor to the Gonads. Development proceeds and the gametogonia turns into oogonia, which become fully surrounded by a layer of cells (pre-granulosa cells). A granulosa cell is a Somatic cell found closely associated with the developing female Gamete (called an Oocyte or egg
Oogonia multiply by dividing mitotically; this proliferation ends when the oogonia enter meiosis. The amount of time that oogonia multiply by mitosis is not species specific. In the human fetus, cells undergoing mitosis are seen until the second and third trimester of pregnancy [3]; [4]. Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female After beginning the meiotic process, the oogonia (now called primary oocytes) can no longer replicate. Therefore the total number of gametes is established at this time. Once the primary oocytes stop dividing the cells enter a prolonged ‘resting phase’. This ‘resting phase’ or dictyate stage can last anywhere up to fifty years in the human. The dictyate or dictyotene is a prolonged resting phase in Oogenesis.
For each primary oocyte that undergoes meiosis, only one functional oocyte is produced. The other two or three cells produced are called polar bodies. A polar body is a cell structure found inside an Ovum. Both Animal and Plant ova possess it Polar bodies have no function and eventually deteriorate.
The primary oocyte turns into a secondary oocyte in mature ovarian follicles. Unlike the sperm, the egg is arrested in the secondary stage of meiosis until fertilization.
Upon fertilization by sperm, the secondary oocyte continues the second part of meiosis and becomes a zygote. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked"
Pathology
Any ovarian follicle that is larger than about two centimeters is termed an ovarian cyst. A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth An ovarian cyst is any collection of fluid surrounded by a very thin wall within an Ovary.
References
- ^ Biology-online
- ^ McGee, E. A. , and Hsueh, A. J. (2000). Initial and cyclic recruitment of ovarian follicles. Endocrine Reviews 21, 200-14.
- ^ Baker, T. G. (1982). Oogenesis and ovulation. In "Book 1: Germ cells and fertilization" (C. R. Austin and R. V. Short, Eds. ), pp. 17-45. Cambridge University Press, Cambridge.
- ^ Byskov, A. G. , and Hoyer, P. E. (1988). Embryology of mammalian gonads and ducts. In "The physiology of reproduction" (E. Knobil and J. Neill, Eds. ), pp. 265-302. Raven Press, Ltd, New York.
Additional images
 Pre-antral follicle |
 Graafian follicles |
External links
- SUNY Labs 43:05-0105 - "The Female Pelvis: The Ovary"
- Histology at BU 14803loa
- Slide at fda.gov
- Images at okstate.edu
- Life cycle at gfmer.ch
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic