Ovary

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Ovarian
)
This article is about the reproductive organ. For the plant part, see Ovary (botany). For other uses, see Ovary (disambiguation).
"Ovaria" redirects here. In botany, this is a proposed section and a synonym of Solanum.
Ovary
Paraaortic lymph node
Identifiers
Latinovarium
MeSHD010053
TA98A09.1.01.001
TA23470
FMA7209
Anatomical terminology]

The ovary is a

Latin ovarium 'egg, nut') found on the left and the right side of the body. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. The ovary progresses through many stages beginning in the prenatal period through menopause. It is also an endocrine gland because of the various hormones that it secretes.[2]

Structure

Each ovary is whitish in color and located alongside the lateral wall of the uterus in a region called the ovarian fossa. The ovarian fossa is the region that is bounded by the external iliac artery and in front of the ureter and the internal iliac artery. This area is about 4 cm x 3 cm x 2 cm in size.[3][4]

The ovaries are surrounded by a capsule, and have an outer cortex and an inner medulla.[4] The capsule is of dense connective tissue and is known as the tunica albuginea.[5]

Usually, ovulation occurs in one of the two ovaries releasing an egg each menstrual cycle.

The side of the ovary closest to the

infundibulopelvic ligament,[3] and the other side points downwards attached to the uterus via the ovarian ligament
.

Other structures and tissues of the ovaries include the hilum.

Ligaments

The ovaries lie within the peritoneal cavity, on either side of the uterus, to which they are attached via a fibrous cord called the

suspensory ligament of the ovary, which is a posterior extension of the broad ligament of the uterus. The part of the broad ligament of the uterus that covers the ovary is known as the mesovarium.[4]

The ovarian pedicle is made up part of the fallopian tube, mesovarium, ovarian ligament, and ovarian blood vessels.[6]

Microanatomy

The surface of the ovaries is covered with a membrane consisting of a lining of simple cuboidal-to-columnar shaped mesothelium,[7] called the germinal epithelium.

ovarian medulla.[8]
It can be hard to distinguish between the cortex and medulla, but follicles are usually not found in the medulla.

Follicular cells are flat epithelial cells that originate from surface epithelium covering the ovary. They are surrounded by granulosa cells that have changed from flat to cuboidal and proliferated to produce a stratified epithelium.

The ovary also contains

lymphatics.[9]

Function

At puberty, the ovary begins to secrete increasing levels of hormones. Secondary sex characteristics begin to develop in response to the hormones. The ovary changes structure and function beginning at puberty.[2] Since the ovaries are able to regulate hormones, they also play an important role in pregnancy and fertility. When egg cells (oocytes) are released from the fallopian tube, a variety of feedback mechanisms stimulate the endocrine system, which cause hormone levels to change.[10] These feedback mechanisms are controlled by the hypothalamus and pituitary glands. Messages or signals from the hypothalamus are sent to the pituitary gland. In turn, the pituitary gland releases hormones to the ovaries. From this signaling, the ovaries release their own hormones.

Gamete production

Main article: Oogenesis
The process of ovulation and gamete production, oogenesis, in a human ovary

The ovaries are the site of production and periodical release of

follicles. Typically, only one oocyte develops at a time, but others can also mature simultaneously. Follicles are composed of different types and number of cells according to the stage of their maturation, and their size is indicative of the stage of oocyte development.[11]
: 833 

When an oocyte completes its maturation in the ovary, a surge of

implantation of the embryo.[11]
: 839 

Hormone secretion

At maturity, ovaries secrete

reproductive organs in their mature functional state. Progesterone prepares the uterus for pregnancy, and the mammary glands for lactation. Progesterone functions with estrogen by promoting menstrual cycle changes in the endometrium.[medical citation needed
]

Ovarian aging

As women age, they experience a decline in reproductive performance leading to menopause. This decline is tied to a decline in the number of ovarian follicles. Although about 1 million oocytes are present at birth in the human ovary, only about 500 (about 0.05%) of these ovulate, and the rest are wasted. The decline in ovarian reserve appears to occur at a constantly increasing rate with age,[17] and leads to nearly complete exhaustion of the reserve by about age 52. As ovarian reserve and fertility decline with age, there is also a parallel increase in pregnancy failure and meiotic errors resulting in chromosomally abnormal conceptions. The ovarian reserve and fertility perform optimally around 20–30 years of age.[18] Around 45 years of age, the menstrual cycle begins to change and the follicle pool decreases significantly.[18] The events that lead to ovarian aging remain unclear. The variability of aging could include environmental factors, lifestyle habits or genetic factors.[18]

Women with an inherited mutation in the DNA repair gene BRCA1 undergo menopause prematurely,[19] 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.[20] 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).[21] Homologous recombinational repair is especially promoted during meiosis. Titus et al.[20] 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.[22][23]

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.[24]

Clinical significance

Polycystic ovaries typically found in polycystic ovarian syndrome

endocrine disorders or as a disorders of the reproductive system.[medical citation needed
]

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.

Notes Ref(s)
Ovarian tumors
Germ cell tumor Seen most often in young women or adolescent girls. Other germ cell tumors are: Endodermal sinus tumor and teratoma, [25]
Ovarian cancer includes
ovarian epithelial cancer
 [26][27][28]
Luteoma Seen in pregnancy
Ovaritis
 Synonym of oophoritis [16]
Ovarian remnant syndrome Incomplete removal of tissue during oophorectomy [16][29]
Endometriosis Often seen in a variety of reproductive regions including

the ovaries.

[30]
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 		[31]
Ovarian torsion Occurs in rare cases. Can occur in all ages [32]
Ovarian apoplexy (rupture) Most often results from ovarian cysts. In rare instances this condition can cause hemorrhaging and death. [33]
Premature ovarian failure
 This disorder is linked to genetic, environmental and autoimmune conditions [34]
Polycystic ovarian syndrome Affects women of reproductive age [30]
Anovulation Caused by a variety of conditions [35]
Follicular cyst of ovary Can occur after menopause, or during childbearing years [36]
Theca lutein cyst Normally occurs postpartum [37]
Chocolate cyst
 Presence of this type of cyst is an indicator of endometriosis [38]
Ovarian germ cell tumors
Benign
 [39]
Dysgerminoma Typically occurs in young women between the ages of 10–30 years of age [40]
Choriocarcinoma Can occur without gynecological symptoms [41]
Yolk sac tumor
 Malignant. Occurs in young children [42]
Teratoma Very rare. Often occurs in newborns [medical citation needed]
Ovarian serous cystadenoma
Benign
lesions 		[43]
Serous cystadenocarcinoma Malignant. Low survival rates [44]
Mucinous cystadenocarcinoma Rare and malignant [44]
Brenner tumor This benign tumor is often found in post-menopausal women [45]
Granulosa cell tumor Rare. Increases estrogen levels. [46]
Krukenberg tumor Metastatic with origins from the stomach [47]
Ovarian torsion. Present in rats.

Society and culture

Cryopreservation

graft rejection, and tissue can be harvested later when mature follicles have developed.[51]

History

In former centuries, medical authors, for example Galen, referred to a woman's ovaries as "female testes".

Other animals

Ovary of a marine fish and its parasite, the nematode Philometra fasciati

Birds have only one functional ovary (the left), while the other remains vestigial. In mammals including humans, the female ovary is homologous to the male testicle, in that they are both gonads and endocrine glands. Ovaries of some kind are found in the female reproductive system of many invertebrates that employ sexual reproduction. However, they develop in a very different way in most invertebrates than they do in vertebrates, and are not truly homologous.[52]

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,

elasmobranch fish; in other species, the remnants of the follicle are quickly resorbed by the ovary. In birds, reptiles, and monotremes, the egg is relatively large, filling the follicle, and distorting the shape of the ovary at maturity.[52]

Amphibians and reptiles have no ovarian medulla; the central part of the ovary is a hollow, lymph-filled space.[53]

The ovary of

jawless fish, and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.[52]

Additional images

  • Left ovary
    Left ovary
  • Ovaries
    Ovaries

See also

References

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Bibliography

External links

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