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any small spherical group of cells containing a cavity

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小嚢(しょうのう),卵胞 / (植物の)袋果(たいか)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/12/21 17:07:36」(JST)

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An antral follicle (or secondary follicle) is an ovarian follicle during a certain latter stage of folliculogenesis.

Definitions differ in where the shift into an antral follicle occurs in the staging of folliculogenesis, with some stating that it occurs when entering the secondary stage,^[1] and others stating that it occurs when entering the tertiary stage.^[2]

Appearance

It is marked by the formation of a fluid-filled cavity adjacent to the oocyte called the antrum. The basic structure of the mature follicle has formed and no novel cells are detectable. Granulosa and theca cells continue to undergo mitosis concomitant with an increase in antrum volume. Antral follicles can attain a tremendous size that is hampered only by the availability of follicle stimulating hormone (FSH), which it is dependent on in this stage of folliculogenesis.

By command of an oocyte-secreted morphogenic gradient, the antral follicle's granulosa cells begin to differentiate themselves into four distinct subtypes: corona radiata that surrounds the zona pellucida, membrana that's interior to the basal lamina, periantral that's adjacent to the antrum, and cumulus oophorus that connects the membrana and corona radiata granulosa cells together. Each type of cell behaves differently in response to FSH.

Endocrine properties

Theca cells express receptors for luteinizing hormone (LH). LH kicks off the production of androgens by the theca cells, most notably androstenedione, which are aromatized by granulosa cells to produce estrogens, primarily estradiol. Consequently, estrogen levels begin to rise.

Antral follicle count

The antral follicle count (AFC) is the number of antral follicles, generally in both ovaries taken together if not else specified. It can be determined by transvaginal ultrasonography.

A low AFC is a major factor in the diagnosis of poor ovarian reserve, that is, low fertility characterized by low numbers of remaining oocytes in the ovaries, usually accompanied by high follicle stimulating hormone (FSH) levels. Several studies show that an AFC test is more accurate than basal FSH testing for older women (< 44 years of age) in predicting IVF outcome.^[3] However, it does not appear to add any predictive information about success rates of an already established pregnancy after IVF.^[4]

It is also a major determinant of the success of ovarian hyperstimulation.

It has been suggested that counting the antral follicles measuring 2–5 or 4–6 mm in diameter is preferable. On the other hand, the number of smaller antral follicles (2–5 mm) is highly correlated with the total number of antral follicles (2–10 mm), and therefore it is suggested that counting all identifiable antral follicles of 2–10 mm in diameter would provide the most practical method for assessment of AFC in clinical practice.^[5]

Three-dimensional (3D) automated follicular tracking is a developing technique that can substantially decrease both intra- and inter-observer variability in estimating the AFC.^[5]

References

^ Page 769, section "formation of the antrum" in: Sherwood, Lauralee. (2010). Human physiology : from cells to system. Australia ; United States: Brooks/Cole. ISBN 978-0-495-39184-5.
^ Page 76 in: Vandenhurk, R.; Bevers, M.; Beckers, J. (1997). "In-vivo and in-vitro development of preantral follicles". Theriogenology 47: 73–82. doi:10.1016/S0093-691X(96)00341-X.
^ Klinkert, Ellen R, et al.,2005. "The antral follicle count is a better marker than basal follicle-stimulating hormone for the selection of older patients with acceptable pregnancy prospects after in vitro fertilization." Fertility and Sterility, 83(3), 811-814.
^ Broer, S. L.; Van Disseldorp, J.; Broeze, K. A.; Dolleman, M.; Opmeer, B. C.; Bossuyt, P.; Eijkemans, M. J. C.; Mol, B. -W. J.; Broekmans, F. J. M.; Import Study, S. L.; Van Disseldorp, J.; Broeze, K. A.; Dolleman, M.; Opmeer, B. C.; Anderson, R. A.; Ashrafi, M.; Bancsi, L.; Caroppo, L. E.; Copperman, A.; Ebner, T.; Eldar Geva, M.; Erdem, M.; Greenblatt, E. M.; Jayaprakasan, K.; Fenning, R.; Klinkert, E. R.; Kwee, J.; Lambalk, C. B.; La Marca, A.; McIlveen, M. (2012). "Added value of ovarian reserve testing on patient characteristics in the prediction of ovarian response and ongoing pregnancy: An individual patient data approach". Human Reproduction Update 19 (1): 26–36. doi:10.1093/humupd/dms041. PMID 23188168.
^ ^a ^b La Marca, A.; Sunkara, S. K. (2013). "Individualization of controlled ovarian stimulation in IVF using ovarian reserve markers: From theory to practice". Human Reproduction Update 20 (1): 124–40. doi:10.1093/humupd/dmt037. PMID 24077980.

UpToDate Contents

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1. 女性の不妊評価 evaluation of female infertility
2. 月経周期の評価と排卵時期 evaluation of the menstrual cycle and timing of ovulation
3. 体外受精（IFV） in vitro fertilization
4. 思春期における多嚢胞性卵巣症候群の診断的評価 diagnostic evaluation of polycystic ovary syndrome in adolescents
5. 自発性早期卵巣障害（早期卵巣機能不全）の臨床症状および評価 clinical manifestations and evaluation of spontaneous primary ovarian insufficiency premature ovarian failure

English Journal

A delay differential equation model of follicle waves in women.

Panza NM1, Wright AA2, Selgrade JF3.
Journal of biological dynamics.J Biol Dyn.2016 Dec;10(1):200-21. doi: 10.1080/17513758.2015.1115564.
This article presents a mathematical model for hormonal regulation of the menstrual cycle which predicts the occurrence of follicle waves in normally cycling women. Several follicles of ovulatory size that develop sequentially during one menstrual cycle are referred to as follicle waves. The model c
PMID 26674178

Long-term effects of methamphetamine exposure in adolescent mice on the future ovarian reserve in adulthood.

Wang L1, Qu G2, Dong X1, Huang K3, Kumar M4, Ji L1, Wang Y1, Yao J1, Yang S1, Wu R1, Zhang H5.
Toxicology letters.Toxicol Lett.2016 Feb 3;242:1-8. doi: 10.1016/j.toxlet.2015.11.029. Epub 2015 Dec 2.
Currently, there is an increasing prevalence of adolescent exposure to methamphetamine (MA). However, there is a paucity of information concerning the long-term impact of early exposure to MA upon female fertility and ovarian reserve. The aim of this study was to investigate the effect of long-term
PMID 26657179

Mechanisms of fibroblast growth factor signaling in the ovarian follicle.

Price CA1.
The Journal of endocrinology.J Endocrinol.2016 Feb;228(2):R31-43. doi: 10.1530/JOE-15-0414. Epub 2015 Nov 5.
Fibroblast growth factors (FGFs) have been shown to alter growth and differentiation of reproductive tissues in a variety of species. Within the female reproductive tract, the effects of FGFs have been focused on the ovary, and the most studied one is FGF2, which stimulates granulosa cell proliferat
PMID 26542145

Japanese Journal

Effects of reaggregated granulosa cells and oocytes derived from early antral follicles on the properties of oocytes grown in vitro

OI Ayano,TASAKI Hidetaka,MUNAKATA Yasuhisa [他]
The journal of reproduction and development 61(3), 191-197, 2015-06
NAID 40020494107

Resveratrol-induced mitochondrial synthesis and autophagy in oocytes derived from early antral follicles of aged cows

SUGIYAMA Miyako,KAWAHARA-MIKI Ryoka,KAWANA Hirosuke,SHIRASUNA Koumei,KUWAYAMA Takehito,IWATA Hisataka
Journal of Reproduction and Development 61(4), 251-259, 2015
… In this study, we collected oocytes and granulosa cell complexes (OGCs) from early antral follicles (EAFs) of aged cows (> …
NAID 130005094651

Effects of reaggregated granulosa cells and oocytes derived from early antral follicles on the properties of oocytes grown in vitro

OI Ayano,TASAKI Hidetaka,MUNAKATA Yasuhisa,SHIRASUNA Koumei,KUWAYAMA Takehito,IWATA Hisataka
Journal of Reproduction and Development 61(3), 191-197, 2015
… In this study, we examined the effects of reconstructed oocyte–granulosa cell complexes (OGCs) on the development of porcine oocytes derived from early antral follicles (EAFs; … After 14 days of culture, we compared cell number, oocyte diameter, and oocyte chromatin configuration in unmanipulated (natural) OGCs, reconstructed OGCs, and OGCs collected from antral follicles (AFs, 3.0–6.0 mm in diameter). …
NAID 130005077742