Ovarian follicle - wikipedia Ovarian follicle Ovarian follicle Histology section of a mature ovarian follicle. The oocyte is the large, round, pink - staining cell at top center of the image. Details Precursor Cortical cords Identifiers Latin Folliculus ovaricus MeSH D006080 TA A09. 1.01. 013 FMA 18641 Anatomical terminology ( edit on Wikidata ) An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. Women begin puberty with about 400,000 follicles, each with the potential to release an egg cell ( ovum ) at ovulation for fertilization. These eggs are developed once every menstrual cycle. Contents 1 Structure 1.1 Oocyte 1.2 Cumulus oophorus 1.3 Membrana granulosa 1.3. 1 Granulosa cell 1.4 Theca of follicle 2 Development 2.1 Development of oocytes in ovarian follicles 3 Clinical significance 4 Additional images 5 See also 6 References 7 External links Structure Section of vesicular ovarian follicle of cat. X 50. Ovarian follicles are the basic units of female reproductive biology. Each of them contains a single oocyte ( immature ovum or egg cell ). These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single competent oocyte in humans. They also consist of granulosa cells and theca of follicle. Oocyte Main article : Oocyte Once a month, one of the ovaries releases a mature egg ( ovum ), known as an oocyte. The nucleus of such an oocyte is called a germinal vesicle ( see picture ). Cumulus oophorus Main article : Cumulus oophorus Cumulus oophorus is a cluster of cells ( called cumulus cells ) that surround the oocyte both in the ovarian follicle and after ovulation. Membrana granulosa Main article : Membrana granulosa It contains numerous granulosa cells. Granulosa cell Granulosa cells or follicular cells are cells that surround the oocyte within the follicle ; their numbers increase directly in response to heightened levels of circulating gonadotropins or decrease in response to testosterone. They also produce peptides involved in ovarian hormone synthesis regulation. Follicle - stimulating hormone ( FSH ) induces granulosa cells to express luteinizing hormone ( LH ) receptors on their surfaces ; when circulating LH binds to these receptors, proliferation stops. Theca of follicle Main article : Theca of follicle 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 ). Outside the basal lamina, the layers theca interna and theca externa are found. Development Main articles : Folliculogenesis and Ovarian follicle activation Primordial follicles are indiscernible to the naked eye. However, these eventually develop into primary, secondary and tertiary vesicular follicles. Tertiary vesicular follicles ( also called `` mature vesicular follicles '' or `` ripe vesicular follicles '' ) are sometimes called Graafian follicles ( after Regnier de Graaf ). In humans, oocytes are established in the ovary before birth and may lie dormant awaiting initiation for up to 50 years. After rupturing, the follicle is turned into a corpus luteum. Development of oocytes in ovarian follicles Main article : Oogenesis In a larger perspective, the whole folliculogenesis from primordial to preovulatory follicle is located in the stage of meiosis I of ootidogenesis in oogenesis. Embryonic development in males and females follows a common pathway before gametogenesis. Once gametogonia enter the gonadal ridge, however, they attempt to associate with these somatic cells. Development proceeds and the gametogonia turn into oogonia, which become fully surrounded by a layer of cells ( pre-granulosa cells ). The 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. 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. For several primary oocytes that complete meiosis I each month, only one or a few functional oocyte, the dominant follicles, completes maturation and undergoes ovulation. The other follicles that begin to mature will regress and become atretic follicles, eventually deteriorating. 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. Clinical significance Any ovarian follicle that is larger than about two centimeters is termed an ovarian cyst. Ovarian function may be measured by gynecologic ultrasonography of follicular volume. Presently, ovarian follicle volumes can be measured rapidly and automatically from three - dimensionally reconstructed ultrasound images. Rupture of the follicle can result in abdominal pain ( mittelschmerz ) and is to be considered in the differential diagnosis in women of childbearing age. Cryopreservation and culture tissue after cryopreservation. Cryopreservation of ovarian tissue is of interest to women who want to preserve their reproductive function beyond the natural limit, or whose reproductive potential is threatened by cancer therapy, for example in hematologic malignancies or breast cancer. For in vitro culture of follicles, there are various techniques to optimize the growth of follicles, including the use of defined media, growth factors and three - dimensional extracellular matrix support. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Animal studies have generally showed correct imprinted DNA methylation establishment in oocytes resulting from follicle culture. Additional images Primordial ovarian follicle. The oocyte is surrounded by a single layer of flat granulosa cells. A histological slide of a human primary ovarian follicle in greater magnification. See also Antral follicle References Jump up ^ David Krogh ( 2010 ), Biology : A Guide to the Natural World, Benjamin - Cummings Publishing Company, p. 638, ISBN 978 - 0 - 321 - 61655 - 5 Jump up ^ `` What Is an Ovarian Follicle ? ''. wiseGEEK.org. wiseGEEK. Retrieved 24 May 2015. Jump up ^ Luijkx, Tim. `` Ovarian follicle ''. radiopaedia.org. radiopaedia.org. Retrieved 24 May 2015. Jump up ^ Biology - online Jump up ^ Katz : Comprehensive Gynecology, 5th ed. Jump up ^ McGee E.A. ; Hsueh A.J. ( 2000 ). `` Initial and cyclic recruitment of ovarian follicles ''. Endocrine Reviews. 21 ( 2 ) : 200 -- 14. doi : 10.1210 / er. 21.2. 200. PMID 10782364. Jump up ^ 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. Jump up ^ 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. Jump up ^ Salama S, Arbo E, Lamazou F, Levailllant JM, Frydman R, Fanchin R ( April 2010 ). `` Reproducibility and reliability of automated volumetric measurement of single preovulatory follicles using SonoAVC ''. Fertil. Steril. 93 ( 6 ) : 2069 -- 73. doi : 10.1016 / j. fertnstert. 2008.12. 115. PMID 19342038. Jump up ^ http://www.merck.com/mmpe/sec02/ch011/ch011b.html Jump up ^ Isachenko V, Lapidus I, Isachenko E, et al. ( 2009 ). `` Human ovarian tissue vitrification versus conventional freezing : morphological, endocrinological, and molecular biological evaluation ''. Reproduction. 138 ( 2 ) : 319 -- 27. doi : 10.1530 / REP - 09 - 0039. PMID 19439559. Jump up ^ Oktay K, Oktem O ( November 2008 ). `` Ovarian cryopreservation and transplantation for fertility preservation for medical indications : report of an ongoing experience ''. Fertil. Steril. 93 ( 3 ) : 762 -- 8. doi : 10.1016 / j. fertnstert. 2008.10. 006. PMID 19013568. ^ Jump up to : Smitz J, Dolmans MM, Donnez J, et al. ( February 2010 ). `` Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation : implications for fertility preservation ''. Hum Reprod Update. 16 ( 4 ) : 395 -- 414. doi : 10.1093 / humupd / dmp056. PMC 2880913. PMID 20124287. Jump up ^ Anckaert, E. ; De Rycke, M. ; Smitz, J. ( 2012 ). `` Culture of oocytes and risk of imprinting defects ''. Human Reproduction Update. 19 ( 1 ) : 52 -- 66. doi : 10.1093 / humupd / dms042. PMID 23054129. External links Anatomy photo : 43 : 05 - 0105 at the SUNY Downstate Medical Center - `` The Female Pelvis : The Ovary '' Histology image : 14803loa -- Histology Learning System at Boston University Slide at fda.gov Images at okstate.edu Life cycle at gfmer.ch Female reproductive system Internal Adnexa Ovaries Follicles corpus hemorrhagicum luteum albicans Theca of follicle externa interna Follicular antrum Follicular fluid Corona radiata Zona pellucida Membrana granulosa Perivitelline space Other Germinal epithelium Tunica albuginea cortex Cumulus oophorus Stroma Medulla Fallopian tubes Isthmus Ampulla Infundibulum Fimbria Ostium Ligaments Ovarian ligament Suspensory ligament Wolffian vestiges Gartner 's duct Epoophoron Vesicular appendages of epoophoron Paroophoron Uterus Regions Body Uterine cavity Fundus Cervix External orifice Cervical canal Internal orifice Supravaginal portion Vaginal portion Uterine horns Layers Endometrium epithelium Myometrium Perimetrium Parametrium Ligaments Round ligament Broad ligament Cardinal ligament Uterosacral ligament Pubocervical ligament General Uterine glands Vagina Fossa of vestibule of vagina Vaginal fornix Hymen Vaginal rugae Support structures Vaginal epithelium External Vulva Labia Mons pubis Labia majora Anterior commissure Posterior commissure Pudendal cleft Labia minora Frenulum of labia minora Frenulum of clitoris Vulval vestibule Interlabial sulci Bulb of vestibule Vaginal orifice vestibular glands / ducts Bartholin 's glands / Bartholin 's ducts Skene 's glands / Skene 's ducts Clitoris Crus of clitoris Corpus cavernosum Clitoral glans Hood Urethra Urethral crest Other G - spot Urethral sponge Perineal sponge Retrieved from `` https://en.wikipedia.org/w/index.php?title=Ovarian_follicle&oldid=835155149 '' Categories : Mammal female reproductive system Hidden categories : Pages with unresolved properties Talk Contents About Wikipedia Čeština Dansk Deutsch Ελληνικά Español فارسی Français Gaeilge Galego 한국어 Italiano עברית Kreyòl ayisyen Lietuvių मराठी Nederlands 日本 語 Polski Português Русский Slovenščina Suomi Svenska Tagalog Türkçe Українська 中文 19 more Edit links This page was last edited on 6 April 2018, at 22 : 05. 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Question: the release of an egg cell is called
Answer: ovulation