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The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are , secreting various that play a role in the menstrual cycle and Fecundity. The ovary progresses through many stages beginning in the prenatal period through menopause.
The ovaries are surrounded by a capsule, and have an outer cortex and an inner medulla. The capsule is of dense connective tissue and is known as the tunica albuginea.
Usually, ovulation occurs in one of the two ovaries releasing an egg each menstrual cycle.
The side of the ovary closest to the fallopian tube is connected to it by infundibulopelvic ligament, and the other side points downwards attached to the uterus via the ovarian ligament.
Other structures and tissues of the ovaries include the hilum.
The ovarian pedicle is made up part of the fallopian tube, mesovarium, ovarian ligament, and ovarian blood vessels.
of the ovarian cortex from a rhesus monkey showing several round follicles embedded in a matrix of stromal cells. A secondary follicle sectioned through the nucleus of an oocyte is at the upper left, and earlier stage follicles are at the lower right. The tissue was stained with the dyes hematoxylin and eosin.]]The outer layer is the ovarian cortex, consisting of ovarian follicles and stroma in between them. Included in the follicles are the cumulus oophorus, membrana granulosa (and the granulosa cells inside it), corona radiata, zona pellucida, and primary oocyte. Theca of follicle, antrum and liquor folliculi are also contained in the follicle. Also in the cortex is the corpus luteum derived from the follicles. The innermost layer is the ovarian medulla. It can be hard to distinguish between the cortex and medulla, but follicles are usually not found in the medulla.
Ovarian follicle are flat epithelial cells that originate from surface epithelium covering the ovary. They are surrounded by that have changed from flat to cuboidal and proliferated to produce a stratified epithelium.
The ovary also contains and lymphatics.
When an oocyte completes its maturation in the ovary, a surge of luteinizing hormone is secreted by the pituitary gland, which stimulates the release of the oocyte through the rupture of the follicle, a process called ovulation. (2025). 9781437703245, Saunders. ISBN 9781437703245 The follicle remains functional and reorganizes into a corpus luteum, which secretes progesterone in order to prepare the uterus for an eventual implantation of the embryo.
Women with an inherited mutation in the DNA repair gene BRCA1 undergo menopause prematurely, suggesting that naturally occurring DNA damages in oocytes are repaired less efficiently in these women, and this inefficiency leads to early reproductive failure. The BRCA1 protein plays a key role in a type of DNA repair termed homologous recombinational repair that is the only known cellular process that can accurately repair DNA double-strand breaks. Titus et al. showed that DNA double-strand breaks accumulate with age in humans and mice in primordial follicles. Primordial follicles contain oocytes that are at an intermediate (prophase I) stage of meiosis. Meiosis is the general process in eukaryotic organisms by which germ cells are formed, and it is likely an adaptation for removing DNA damages, especially double-strand breaks, from germ line DNA (see Meiosis and Origin and function of meiosis). Homologous recombinational repair is especially promoted during meiosis. Titus et al. also found that expression of 4 key genes necessary for homologous recombinational repair of DNA double-strand breaks (BRCA1, MRE11, RAD51 and ATM) decline with age in the oocytes of humans and mice. They hypothesized that DNA double-strand break repair is vital for the maintenance of oocyte reserve and that a decline in efficiency of repair with age plays a key role in ovarian aging. A study identified 290 genetic determinants of ovarian ageing, also found that DNA damage response processes are implicated and suggests that possible effects of extending fertility in women would improve bone health, reduce risk of type 2 diabetes and increase the risk of hormone-sensitive cancers.
A variety of testing methods can be used in order to determine fertility based on maternal age. Many of these tests measure levels of hormones FSH, and GnrH. Methods such as measuring AMH (anti-Müllerian hormone) levels, and AFC (antral follicule count) can predict ovarian aging. AMH levels serve as an indicator of ovarian aging since the quality of ovarian follicles can be determined.
If the egg fails to release from the follicle in the ovary an ovarian cyst may form. Small ovarian cysts are common in healthy women. Some women have more follicles than usual (polycystic ovary syndrome), which inhibits the follicles to grow normally and this will cause cycle irregularities.
| Germ cell tumor | Seen most often in young women or adolescent girls. Other germ cell tumors are: Endodermal sinus tumor and teratoma, | |
| Ovarian cancer | includes ovarian epithelial cancer | |
| Luteoma | Seen in pregnancy | |
| Ovaritis | Synonym of oophoritis | |
| Ovarian remnant syndrome | Incomplete removal of tissue during oophorectomy | |
| Endometriosis | Often seen in a variety of reproductive regions including the ovaries. | |
| Hypogonadism | It exists in two forms, central and primary. Central hypogonadism is a condition that is a result of improper function from the hypothalamus and pituitary gland. | |
| Hyperthecosis | Theca cells are present within ovarian stroma | |
| Ovarian torsion | Occurs in rare cases. Can occur in all ages | |
| Ovarian apoplexy (rupture) | Most often results from . In rare instances this condition can cause Bleeding and death. | |
| Premature ovarian failure | This disorder is linked to genetic, environmental and autoimmune conditions | |
| Polycystic ovarian syndrome | Affects women of reproductive age | |
| Anovulation | Caused by a variety of conditions | |
| Follicular cyst of ovary | Can occur after menopause, or during childbearing years | |
| Theca lutein cyst | Normally occurs postpartum | |
| Chocolate cyst | Presence of this type of cyst is an indicator of endometriosis | |
| Ovarian germ cell tumors | Benign | |
| Dysgerminoma | Typically occurs in young women between the ages of 10–30 years of age | |
| Choriocarcinoma | Can occur without Gynaecology symptoms | |
| Yolk sac tumor | Malignancy. Occurs in young children | |
| Teratoma | Very rare. Often occurs in newborns | |
| Ovarian serous cystadenoma | Benign lesions | |
| Serous cystadenocarcinoma | Malignancy. Low survival rates | |
| Mucinous cystadenocarcinoma | Rare and Malignancy | |
| Brenner tumour | This benign tumor is often found in post-menopausal women | |
| Granulosa cell tumor | Rare. Increases estrogen levels. | |
| Krukenberg tumor | Metastasis with origins from the stomach |
Herophilos was the first to describe the ovaries and the . He called the ovaries the "female testes", and gave the female equal credit with the male for producing the fetus. He thought the ovaries produced female seeds, and the testicles produced male seeds. The female seeds travel through the fallopian tubes and combine with the male seed in the uterus (not the fallopian tubes), thus producing an embryo. Soranus of Ephesus gave a detailed description of the ovaries. Galen in On Semen argued that both the testicles and the ovaries contribute to embryo, but the testicles contribute more since they are larger. Andreas Vesalius, by dissecting women of reproductive age, discovered the follicles with fluid within "white and like a milky serum", as well as yellow stuff likely to be the corpus luteum. He also noted the ovaries are bumpy with ovulation stigmas. Fabricius observed that in the hen, yolk is formed in the ovary, while the Egg white and the Eggshell are formed during the transit through the oviduct. He also made the first illustration of the corpus luteum in De Formato Foetu (1604) and called it "numerous conjoined little glands". Carlo Ruini noted that the ovaries of fetal mare are up to 4 times as large as the mother's.
Nicolas Steno in 1667 hypothesized that the ovaries of mammals are analogous to the ovaries of birds, and thus they too contain eggs (rather than the "female semen"). In 1675 he described the ovaries of various animals, and hypothesized that she-mules are infertile because their ovaries do not produce eggs. De Graaf made a full-length study of the female reproductive system. De mulierum organis generationi (de Graaf, 1672) He thought the whole follicle was an egg, and proved it by cooking and eating the liquid inside follicles and noting that it had the same color, taste, and consistency as cooked egg-white. He stated that the number of corpus luteum is the same as the number of fetuses, and it only occurs after coitus (he was observing rabbits, who have induced ovulation). He also thought the corpus luteum is the scar tissue left behind after the egg is shed from the ovary. He observed that the corpus luteum is yellow in cows, red in sheep red, and ashen in others. Drelincourt in 1685 De Conceptione adversaria Leiden 1685 suggested that the follicle is not the egg, and that the true egg is much smaller, and within the follicle. Malpighi speculated that the follicle never leaves the ovary, but remains within. The true egg is much smaller and within the follicle, and leaves the ovary. He also coined the word "corpus luteum" Latin because he worked with the cow's ovaries, in which the corpus luteum is yellow. Herman Boerhaave clearly stated the currently accepted theory that the ovum escapes from the ovary, leaving a scar tissue of corpus luteum, and pass down the fallopian tube, be fertilized by a sperm within the tube, then enters the uterus.
There was a controversy during the period about how reproduction works. Some like William Harvey agreed with Aristotle that the ovaries are unimportant. Some like Wharton, Descartes, and Le Grand, agreed with Galen that the ovaries produced female semen that mixes with male semen to produce an embryo. The new "ovism" school like Steno and de Graaf thought the ovaries in mammals worked like the ovaries in birds: The entire follicle is an egg. The egg is fertilized in the ovary. Only fertilized eggs can leave the ovary. The new "Preformationism" school believed only the sperm contained the generative principle.
John Huner experimentally removed one ovary from a sow and compared her with a sow with two ovaries. He noted that the half-spayed sow became infertile after producing 76 piglets, but still continued to go into estrus. The other sow produced 162 piglets, thus he proposed that each ovary could produce a fixed number of offsprings. Percivall Pott reported in 1775 that he removed two herniated ovaries from a woman, after which she became thinner, lost her large breasts, and ceased menstruation. This was the first accurate description of the effect of ovarectomy in humans. In 1827, von Baer first described and illustrated the mammalian egg within the follicle.
Albert Peuch in 1873 stated that spaying young sows prevented subsequent growth in uterus. Emil Knauer showed that transplanting ovaries into the abdominal cavity in spayed gods, rabbits, and guinea pigs prevented this uterine atrophy, similar to the testicle transplant experiment of Berthold in 1849. Auguste Prenant in 1898 concluded by histology that the corpus luteum was an endocrine gland. Ludwig Fraenkel Vilhelm Magnus both showed independently in 1901 that spaying pregnant rabbits or removing their corpora lutea by Cauterization resulted in abortion or resorption of the embryos. Leo Loeb noted in 1906 that traumatizing the endometrium of a nonpregnant guinea pig or rabbit resulted in formation of placenta or Decidualization, but this did not happen if corpora lutea were removed. In 1915, Edmund Herrmann, an Austrian obstetrician, showed that a lipid extract of pig's corpora lutea produced a fully progestational endometrium when injected into immature rabbits. This line of work was continued by Corner and Allen, resulting in the discovery of progesterone. Leo Loeb also showed in 1911 that removing the corpora lutea hastened the next ovulation. (Makepeace et al, 1937) showed specifically that injecting progesterone inhibited ovulation in rabbits. This eventually resulted in hormonal contraception.
Many of the features found in human ovaries are common to all vertebrates, including the presence of follicular cells, tunica albuginea, and so on. However, many species produce a far greater number of eggs during their lifetime than do humans, so that, in fish and amphibians, there may be hundreds, or even millions of fertile eggs present in the ovary at any given time. In these species, fresh eggs may be developing from the germinal epithelium throughout life. Corpora lutea are found only in mammals, and in some elasmobranch fish; in other species, the remnants of the follicle are quickly resorbed by the ovary. In birds, reptiles, and , the egg is relatively large, filling the follicle, and distorting the shape of the ovary at maturity.
Amphibians and reptiles have no ovarian medulla; the central part of the ovary is a hollow, lymph-filled space.
The ovary of is also often hollow, but in this case, the eggs are shed into the cavity, which opens into the oviduct. Certain of the genus Philometra are parasitic in the ovary of marine fishes and can be spectacular, with females as long as , coiled in the ovary of a fish half this length. Although most female vertebrates have two ovaries, this is not the case in all species. In most birds and in , the right ovary never matures, so that only the left is functional. (Exceptions include the kiwi and some, but not all raptors, in which both ovaries persist.) In some elasmobranchs, only the right ovary develops fully. In the primitive jawless fish, and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.
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