A pear-shaped, thick-walled muscular organ of females which projects upwards and forwards above the bladder from the upper part of the vagina; also known as the womb. It consists of a fundus (the region of the body above the level of entrance of the uterine tubes), a body, and the cervix (separated from the body by a slight narrowing). The lower end of the cervix is surrounded by and opens into the upper part of the vagina. At birth the uterus is mainly an abdominal organ, the cervix being relatively large and not distinct from the body. It grows slowly until just before puberty, when its growth is rapid for a time. In old age the uterine wall becomes harder and more fibrous than in the younger woman. The pregnant uterus increases rapidly in size and weight as it rises into the abdomen. In the human female, the nonpregnant uterus is c.7·5 cm/3 in in length and weighs 40 g/1·4 oz. During pregnancy it increases in size to become c.30 cm/12 in in length and can weigh as much as 1 kg/2·2 lb by the eighth month. Immediately after childbirth it contracts, so that by the end of the eighth week it is back to its normal size (this process is known as involution). The epithelial lining (endometrium) is influenced by oestrogens and progestagens produced by the ovary. If implantation does not follow ovulation, the superficial layers of the endometrium are shed in response to hormonal changes, causing the menstrual flow.
Regions
From outside to inside, the path to the uterus is as follows:
Vagina Cervix uteri - "neck of uterus" External orifice of the uterus Canal of the cervix Internal orifice of the uterus corpus uteri - "Body of uterus" Cavity of the body of the uterus Fundus (uterus)Layers
The layers, from innermost to outermost, are as follows:
| Layer | Description |
| endometrium | The lining of the uterine cavity is called the "endometrium". |
| myometrium | The uterus mostly consists of smooth muscle, known as "myometrium". |
| perimetrium | The loose surrounding tissue is called the "perimetrium". |
| peritoneum | The uterus is surrounded by "peritoneum". |
Ligaments
It is held in place by the following ligaments:
| Name | Number | Description |
| anterior | one | vesicouterine fold of peritoneum |
| posterior | one | rectovaginal fold of peritoneum |
| lateral or broad ligament of the uterus (mesometrium) | two | part of peritoneum that extends from the sides of the uterus |
| uterosacral ligaments | two | rectouterine folds |
| round ligament of uterus | two | from lateral angle of the uterus to labium majus |
| ovarian ligaments | two | connect uterus to ovaries |
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 |
Development
The bilateral Müllerian ducts form during early fetal life.
Pathology
Some pathological states include:
Prolapse of the uterus Carcinoma of the cervix - malignant neoplasm Carcinoma of the uterus - malignant neoplasm Ectopic pregnancy Fibroids - benign neoplasms Adenomyosis - ectopic growth of endometrial tissue within the myometrium Pyometra - infection of the uterus, most commonly seen in dogsTerminology
The term uterus is commonly used within the medical and related professions, whilst the term womb is in more common usage.
Additional images
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Schematic frontal view of female anatomy |
Uterus and uterine tubes. |
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