Ovary

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. 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, The ovarian pedicle is made up of the fallopian tube, mesovarium, ovarian ligament, and ovarian blood vessels. Microanatomy The surface of the ovaries is covered with a membrane consisting of a lining of simple cuboidal-to-columnar shaped mesothelium, called the germinal epithelium. 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. Follicular cells are flat epithelial cells that originate from the 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 blood vessels and lymphatics. ==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. 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 The ovaries are the site of production and periodical release of egg cells, the female gametes. In the ovaries, the developing egg cells (or oocytes) mature in the fluid-filled follicles. Typically, only one oocyte develops at a time, but others can also mature simultaneously. Follicles are composed of different types and numbers of cells according to the stage of their maturation, and their size is indicative of the stage of oocyte development. 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. The follicle remains functional and reorganizes into a corpus luteum, which secretes progesterone to prepare the uterus for an eventual implantation of the embryo. inhibin, and progestogen. 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. Around 45 years of age, the menstrual cycle begins to change and the follicle pool decreases significantly. 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, which 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 damage, 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. A variety of testing methods can be used 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 follicle count) can predict ovarian aging. AMH levels serve as an indicator of ovarian aging since the quality of ovarian follicles can be determined. ==Clinical significance==

Ovarian diseases can be classified as endocrine disorders or as a disorders of the reproductive system. 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 from growing normally, and this will cause cycle irregularities. . Present in rats. ==Society and culture==

Cryopreservation Cryopreservation of ovarian tissue, often called ovarian tissue cryopreservation, 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. A study of 60 procedures concluded that ovarian tissue harvesting appears to be safe. The ovarian tissue may also be transplanted into mice that are immunocompromised (SCID mice) to avoid graft rejection, and tissue can be harvested later when mature follicles have developed. History Aristotle referred to ovarectomy in Historia Animalium, in sows to stimulate growth and fatness, and in female war camels to sterilize them. However, he believed that embryos are formed when the seed of a male (produced by the sperm ducts, rather than the testicles) plants into the soil of a female (probably referring to menstrual blood), and did not subscribe to the significance of gonads in heredity. He also observed that spayed females cease to go into estrus. Herophilus was the first to describe the ovaries and the oviducts. 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. De Graaf made a full-length study of the female reproductive system. 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, and ashen in others. Drelincourt in 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 for "yellow body"] because he worked with the cow's ovaries, in which the corpus luteum is yellow. Boerhaave clearly stated the currently accepted theory that the ovum escapes from the ovary, leaving scar tissue of the corpus luteum, and passes down the fallopian tube, is fertilized by a sperm within the tube, then enters the uterus. Percival 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 ovariectomy in humans. In 1827, von Baer first described and illustrated the mammalian egg within the follicle. 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 thermocautery 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 deciduoma, 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. ==Other animals==

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. 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 monotremes, the egg is relatively large, filling the follicle and distorting the shape of the ovary at maturity. The ovary of teleosts is also often hollow, but in this case, the eggs are shed into the cavity, which opens into the oviduct. Although most female vertebrates have two ovaries, this is not the case in all species. In most birds and in platypuses, 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. ==Additional images==

File:Slide1DDD.JPG|Left ovary File:Ovaries.jpg|Ovaries File:Uterus and ovaries.png|Uterus, fallopian tubes, and ovaries File:Right ovary.png|Right ovary ==See also==