Uterus

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This article is about female reproductive anatomy. For the nightclub in Shibuya, Tokyo, see Womb (nightclub).

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Uterus

Human female internal reproductive anatomy

1. Round ligament 2. Uterus 3. Uterine cavity 4. Intestinal surface of Uterus 5. Versical surface(toward bladder) 6. Fundus of uterus 7. Body of uterus 8. Palmate folds of cervical canal 9. Cervical canal 10. Posterior lip 11. Cervical os (external) 12. Isthmus of uterus 13. Supravaginal portion of cervix 14. Vaginal portion of cervix 15. Anterior lip 16. Cervix
Gray's	subject #268 1258
Artery	ovarian artery, uterine artery, helicine branches of uterine artery
Vein	uterine veins
Lymph	body and cervix to internal iliac lymph nodes, fundus to para-aortic lymph nodes
Precursor	Müllerian duct
MeSH	Uterus

The uterus (Latin word for womb) is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation. The term uterus is used consistently within the medical and related professions; the Germanic term, womb is more common in everyday usage. The plural of uterus is uteruses or uteri.

One end, the cervix, opens into the vagina; the other is connected on both sides to the Fallopian tubes.

[edit] Function

The uterus provides structural integrity and support to the bladder, bowel, pelvic bones and organs. The uterus helps separate and keep the bladder in its natural position above the pubic bone and the bowel in its natural configuration behind the uterus. The uterus is continuous with the cervix, which is continuous with the vagina, much in the way that the head is continuous with the neck, which is continuous with the shoulders. It is attached to bundles of nerves, and networks of arteries and veins, and broad bands of ligaments such as round ligaments, cardinal ligaments, broad ligaments, and uterosacral ligaments [1].

The uterus is essential in sexual response by directing blood flow to the pelvis and to the external genitalia, including the ovaries, vagina, labia, and clitoris. The uterus is needed for uterine orgasm to occur.

The reproductive function of the uterus is to accept a fertilized ovum which becomes implanted into the endometrium, and derives nourishment from blood vessels which develop exclusively for this purpose. The fertilized ovum becomes an embryo, develops into a fetus and gestates until childbirth. Due to anatomical barriers such as the pelvis, the uterus is pushed partially into the abdomen due to its expansion during pregnancy. Even during pregnancy the mass of a human uterus amounts to only about a kilogram (2.2 pounds).

[edit] Forms in mammals

In mammals, the four main forms in which it is found are:

Bipartite: Found in ungulates (deer, moose, elk etc.), and in carnivores (cats, and dogs).
Bicornuate: Found in pigs.
Simplex: Found in humans, other primates and horses.
Duplex: Found in rodents (such as mice, rats and guinea pigs), marsupials and lagomorpha (rabbits and hares).

[edit] Anatomy

The uterus is located inside the pelvis immediately dorsal (and usually somewhat rostral) to the urinary bladder and ventral to the rectum. Outside of pregnancy, its size in humans is several centimeters in diameter. The uterus is a pear shaped muscular organ which can be divided anatomically into four segments: The fundus, corpus, cervix and the internal os.

[edit] Regions

From outside to inside, the path to the uterus is as follows:

Vulva
Vagina
Cervix uteri - "neck of uterus"
corpus uteri - "Body of uterus"
- Cavity of the body of the uterus
- Fundus (uterus)

[edit] Layers

The layers, from innermost to outermost, are as follows:

Endometrium: The lining of the uterine cavity is called the "endometrium." It consists of the functional endometrium and the basal endometrium from which the former arises. In most mammals, including humans, the endometrium builds a lining periodically which is shed or reabsorbed if no pregnancy occurs. Shedding of the functional endometrial lining in humans is responsible for menstrual bleeding (known colloquially as a woman's "period") throughout the fertile years of a female and for some time beyond. In other mammals there may be cycles set as widely apart as six months or as frequently as a few days.
Myometrium: The uterus mostly consists of smooth muscle, known as "myometrium." The innermost layer of myometrium is known as the junctional zone, which becomes thickened in adenomyosis.
Perimetrium: The loose surrounding tissue is called the "perimetrium."
Peritoneum: The uterus is surrounded by "peritoneum."

[edit] Support

The uterus is primarily supported by the pelvic diaphragm,perineal body and the urogenital diaphragm. Secondarily, it is supported by ligaments and the peritoneum (broad ligament of uterus) ^[1]

[edit] Major ligaments

It is held in place by several peritoneal ligaments, of which the following are the most important (there are two of each):

Name	From	To
uterosacral ligament	the posterior cervix	the sacrum of pelvis
cardinal ligaments	the side of the cervix	the ischial spines
pubocervical ligament ^[1]	the side of the cervix	the pubic symphysis

Other named ligaments near the uterus, i.e. the broad ligament, the round ligament, the suspensory ligament of the ovary, the infundibulopelvic ligament, have no role in the support of the uterus.

[edit] Position

Under normal circumstances the uterus is both "anteflexed" and "anteverted." The meaning of these terms are described below:

Distinction	More common	Less common
Position tipped	"anteverted": tipped forward	"retroverted": tipped backwards
Position of fundus	"anteflexed": the fundus is pointing forward relative to the cervix	"retroflexed": the fundus is pointing backwards

[edit] Development

The bilateral Müllerian ducts form during early fetal life. In males, MIF secreted from the testes leads to their regression. In females these ducts give rise to the Fallopian tubes and the uterus. In humans the lower segments of the two ducts fuse to form a single uterus, however, in cases of uterine malformations this development may be disturbed. The different uterine forms in various mammals are due to various degrees of fusion of the two Müllerian ducts.

[edit] Sexual response

Main article: Uterine orgasm

Stimulation of the uterus can result in an intense orgasm.

[edit] Pathology

[edit] Additional images

Schematic frontal view of female anatomy	Uterus and uterine tubes.		Anatomical model of a human pregnancy
Sectional plan of the gravid uterus in the third and fourth month.	Fetus in utero, between fifth and sixth months.	Vessels of the uterus and its appendages, rear view.	Uterus and right broad ligament, seen from behind.
Female pelvis and its contents, seen from above and in front.	Sagittal section of the lower part of a female trunk, right segment.	Posterior half of uterus and upper part of vagina.	The arteries of the internal organs of generation of the female, seen from behind.
Median sagittal section of female pelvis.