Graafian follicle


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Related to Graafian follicle: ovarian follicle, ovulation, corpus luteum

graafian follicle

 [graf´e-an]
a small sac, embedded in the ovary, that encloses an ovum. At puberty each ovary has a large number of immature follicles (primordial follicles), each of which contains an undeveloped egg cell.

About every 28 days between puberty and the onset of menopause, one of the follicles develops to maturity, or ripens, into a graafian follicle (or vesicular ovarian follicle). As it ripens, it increases in size. The ovum within becomes larger, the follicular wall becomes thicker, and fluid collects in the follicle and surrounds the ovum. The follicle also secretes estradiol, the hormone that prepares the endometrium to receive a fertilized egg. As the follicle matures, it moves to the surface of the ovary and forms a projection. When fully mature, the graafian follicle breaks open and releases the ovum, which passes into the fallopian tubes. This release of the ovum is called ovulation; it occurs midway in the menstrual cycle, generally about 14 days after the commencement of the menstrual flow.

The released ovum travels down the tube to the uterus, a process that takes about 3 days. Meanwhile, the empty graafian follicle in the ovary becomes filled with cells containing a yellow substance, the corpus luteum. The corpus luteum secretes progesterone, a hormone that causes further change in the endometrium, allowing it to provide a good milieu in which a zygote (fertilized ovum) can grow through the stages of gestation to become a fetus.

ve·sic·u·lar o·var·i·an fol·li·cle

[TA]
a follicle in which the primary oocyte attains its full size and is surrounded by an extracellular glycoprotein layer (zona pellucida) that separates it from a peripheral layer of follicular cells permeated by one or more fluid-filled antra; the primary oocyte occupies the cumulus oophorus; the theca of the follicle develops into internal and external layers.

Graafian follicle

(grä′fē-ən, grăf′ē-)
n.
Any of the fluid-filled vesicles in the mammalian ovary containing a maturing ovum.

ve·sic·u·lar o·var·i·an fol·li·cle

(vĕ-sik'yū-lăr ō-var'ē-ăn fol'i-kĕl) [TA]
A follicle in which the oocyte attains its full size and is surrounded by an extracellular glycoprotein layer (zona pellucida) that separates it from a peripheral layer of follicular cells permeated by one or more fluid-filled antra; the theca of the follicle develops into internal and external layers.
Synonym(s): antral follicle, graafian follicle, secondary follicle.

Graafian follicle

A nest of cells in the ovary that develops into a fluid-filled cyst containing a maturing egg (ovum). One or more of these develops in each menstrual cycle, releasing one or more ova into the FALLOPIAN TUBE and leaving behind the CORPUS LUTEUM. (Regnier de Graaf, 1641–73, Dutch anatomist).
Graafian follicleclick for a larger image
Fig. 179 Graafian follicle . General structure.

Graafian follicle

a structure in the ovary of a female mammal, consisting of an OOCYTE surrounded by granular FOLLICLE cells which enclose also a large, fluid filled cavity, the whole structure being encased in a wall of connective tissue. See Fig. 179 . The Graafian follicle begins to form deep inside the ovary, stimulated by FSH as the OESTROUS CYCLE develops, gradually enlarging and maturing as it moves to the surface, eventually appearing like a blister on the surface, just prior to release of the oocyte (ovulation) by rupture of the wall. After ovulation the follicle becomes a CORPUS LUTEUM. Further ovulation is normally prevented by the corpus luteum secreting PROGESTERONE, which in turn inhibits FSH production by the PITUITARY GLAND, so no further follicles develop. The presence of the cavity distinguishes the Graafian follicle (named after Regnier de Graaf) from the OVARIAN FOLLICLES of other vertebrates.

Graaf,

Reijnier de, Dutch physiologist and histologist, 1641-1673.
graafian follicle - a follicle in which the oocyte attains its full size. Synonym(s): vesicular ovarian follicle
References in periodicals archive ?
The differences of Graafian follicles in the control and cyclophosphamide-treated group was however not significant.
The histological structures of the primary secondary and graafian follicles derived from the groups of cyclophosphamide pre-treated with NSO were more preserved than that achieved from cyclophosphamide-alone group.
TABLE 2: Comparison of mean number of atretic and cystic primordial, growing, and graafian follicles and corpus luteum in PCO and control groups.
However, the shape of the ovary was greatly changed due to the presence of Graafian follicles or the corpora lutea.
However, for the right ovary, mean numbers of active Graafian follicles was significantly (p<0.05) higher during the peak than the low breeding season.
Among 92 camels, four had plain ovaries without any Graafian follicles, while 18 had follicles of 5 mm or less in diameter and were considered as inactive.
Follicles were classified based on their morphological characteristics as: primordial, primary, secondary and Graafian follicles.
Visibly, administration of nicotine for 15 days caused a significant decrease in the number of secondary and Graafian follicles (p < 0.05) in comparison with the controls.
Co-administration of nicotine and melatonin significantly increased number of secondary and Graafian follicles and corpus luteum in compareson with the nicotine only treated mice (Table 1).