ovary


ovary
/oh"veuh ree/, n., pl. ovaries.
1. Anat., Zool. the female gonad or reproductive gland, in which the ova and the hormones that regulate female secondary sex characteristics develop.
2. Bot. the enlarged lower part of the pistil in angiospermous plants, enclosing the ovules or young seeds.
[1650-60; < NL ovarium. See OVUM, -ARY]

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In zoology, the female reproductive organ (see reproductive system) that produces eggs and sex hormones (estrogen and progesterone).

Human females have two ovaries, almond-shaped organs about 1.5 in. (4 cm) long. They contain hollow balls of cells (follicles) that hold immature eggs. About 150,000–500,000 follicles usually are present at birth; by young adulthood, only about 34,000 remain. The number continues to decrease until menopause, when the few remaining follicles decay and the ovaries shrink and produce far less estrogen. Only 300–400 follicles mature and release an egg, which develops into an embryo if fertilized or, if not, passes from the body with menstruation. In botany, an ovary is the enlarged base of a flower's female organ (pistil). It contains ovules, which develop into seeds when fertilized, and matures into a fruit.

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▪ animal and human
      in zoology, female reproductive organ in which sex cells (eggs or ova) are produced. The usually paired ovaries of female vertebrates produce both the sex cells and the hormones necessary for reproduction. In some invertebrate groups such as coelenterates, formation of ovaries is associated with the seasons. Many invertebrates have both ovaries and testes in one animal, and some species undergo sex reversal. See also egg; gonad.

      In humans, ovaries of the newborn and young child are a mass of elongated tissue; as the female reaches adolescence, the ovaries gradually enlarge and change their shape. The adult ovaries are almond-shaped and are about 4 centimetres (1.6 inches) long, 2 centimetres (0.8 inch) wide, and 1.5 centimetres (0.6 inch) thick; the two ovaries weigh from 4 to 8 grams (0.15 to 0.3 ounce). The ovaries are attached to the uterus and the fallopian tubes by several ligaments. The surfaces of the ovaries are usually uneven and have areas of scar tissue. Hollow balls of cells—follicles—containing immature egg cells are present in the ovaries at birth; there are usually 150,000 to 500,000 follicles at this time. When the female reaches adolescence and young adulthood, the number has been reduced to only about 34,000. As a woman ages, the follicles gradually diminish in number until, at menopause and the cessation of reproductive powers, the few remaining follicles degenerate. During the active child-bearing years, normally between the ages 13 and 50, only 300 to 400 of the follicles undergo maturation. In about every four weeks of the active reproductive years, one follicle from only one of the two ovaries matures; the egg inside the follicle is extruded from the ovary into the rest of the reproductive tract for fertilization. If the egg is not fertilized by the male sperm, it passes from the body during the process of menstruation (q.v.).

      The ovaries also function as endocrine (endocrine system, human) glands by secreting two hormones, estrogen and progesterone, into the bloodstream. Estrogen, which is secreted by the ovarian follicle, controls the development of the secondary sex characteristics such as enlargement of the breasts, growth of pubic hair, and the increased amount of fat on the hips and buttocks; estrogen also stimulates growth of the uterine lining during the menstrual cycle. progesterone is secreted from the cells of the corpus luteum, a body that develops at the site of the mature follicle upon release of the egg. Progesterone helps the fertilized egg to secure itself to the uterus and to develop into an embryo.

      The centre of the ovary, called the medulla, is a core of connective tissue consisting of blood vessels, lymphatic ducts, and nerve fibres. The thick layer covering the medulla is the cortex, which contains the follicles and ova. As a follicle matures, it enlarges and migrates to the surface of the ovary. When an egg is discharged from a follicle, blood and yellow cells move into the empty follicular cavity to fill it; this tissue becomes the corpus luteum. If the egg is fertilized, the corpus luteum remains until the end of pregnancy; (pregnancy) during this time the corpus luteum secretes progesterone. If the ovum is not fertilized, the corpus luteum becomes a whitish scar mass, known as corpus albicans, which, usually, eventually disappears.

      After menopause, the ovaries shrink in size and usually consist of old fibrous tissue. The production of estrogen drops considerably but does not totally cease. See also ovulation.

plant
      in botany, enlarged basal portion of the pistil, the female organ of a flower. The ovary contains ovules (ovule), which develop into seeds upon fertilization. It will mature into a fruit, either dry and parchmentlike or fleshy, enclosing the seeds.

      A simple or unicarpellate ovary is formed from a single carpel, an evolutionarily modified leaf. It has one chamber (locule), within which are the ovules. A multicarpellate ovary consists of more than one carpel and may have one or more locules.

  Ovary position is a useful feature in classification. An ovary attached to the receptacle above the attachment of other floral parts is termed superior (see photograph—>); when it lies below the attachment of other floral parts, it is inferior (see photograph—>). See also flower.
 

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Universalium. 2010.

Look at other dictionaries:

  • ovary — (n.) 1650s, from Mod.L. ovarium ovary (16c.), from M.L. ovaria the ovary of a bird (13c.), from L. ovum egg, from PIE *owyo /*oyyo egg (see EGG (Cf. egg) (n.)). In classical Latin, ovarius meant egg keeper …   Etymology dictionary

  • Ovary — O va*ry ([=o] v[.a]*r[y^]), n.; pl. {Ovaries} ([=o] v[.a]*r[i^]z). [NL. ovarium, fr. L. ovum egg: cf. F. ovaire. See {Oval}.] 1. (Bot.) That part of the pistil which contains the seed, and in most flowering plants develops into the fruit. See… …   The Collaborative International Dictionary of English

  • ovary — ovary. См. завязь. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • ovary — ovary. См. яичник. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Óváry — (spr. ōwāri), Leopold, Ritter von, ungar. Historiker, geb. 31. Dez. 1833 in Veszprim, nahm 1848–49 am ungarischen und 1860 am italienischen Freiheitskampf teil und wurde 1867 in das ungarische Landesarchiv berufen, das er gegenwärtig als… …   Meyers Großes Konversations-Lexikon

  • ovary — ► NOUN (pl. ovaries) 1) a female reproductive organ in which ova or eggs are produced. 2) Botany the base of the carpel of a flower, containing one or more ovules. ORIGIN Latin ovarium, from ovum egg …   English terms dictionary

  • ovary — [ō′və rē] n. pl. ovaries [ModL ovarium < L ovum,EGG1] 1. Anat. Zool. a female reproductive gland producing eggs and, in vertebrates, sex hormones 2. Bot. the enlarged, hollow part of the pistil or gynoecium, containing ovules: see PISTIL… …   English World dictionary

  • Ovary — For ovary as part of plants, see ovary (plants). Ovaria redirects here. This is also a proposed section and a synonym of Solanum. Ovary Blood supply of the human female reproductive organs. The left ovary is visible above the label …   Wikipedia

  • ovary — Female reproductive organ, producing ova [Butler, T.H.]. In free living copepod unpaired, parasitic copepod paired, expanded section of female reproductive system in which eggs are produced. Located dorsally, above midgut, near border of head and …   Crustacea glossary

  • Ovary — The female gonad, the ovary is one of a pair of reproductive glands in women. They are located in the pelvis, one on each side of the uterus. Each ovary is about the size and shape of an almond. The ovaries produce eggs (ova) and female hormones …   Medical dictionary


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