: cervices) or cervix uteri is a dynamic fibromuscular sexual organ of the female reproductive system that connects the vagina with the uterine cavity.

[4] To the rear, the supravaginal cervix is covered by peritoneum, which runs onto the back of the vaginal wall and then turns upwards and onto the rectum, forming the recto-uterine pouch.

[7] The cervical canal varies greatly in length and width between women or over the course of a woman's life,[3] and it can measure 8 mm (0.3 inch) at its widest diameter in premenopausal adults.

[11] After menstruation and directly under the influence of estrogen, the cervix undergoes a series of changes in position and texture.

However, as ovulation approaches, the cervix becomes softer and rises to open in response to the higher levels of estrogen present.

During development, the outer parts of the two ducts fuse, forming a single urogenital canal that will become the vagina, cervix and uterus.

[15]: 15–16  New studies show, however, that all the cervical as well as large part of the vaginal epithelium are derived from Müllerian duct tissue and that phenotypic differences might be due to other causes.

[17]: 411  Upon entering puberty, due to hormonal influence, and during pregnancy, the columnar epithelium extends outward over the ectocervix as the cervix everts.

[17]: 410–411  A buildup of mucus in the glands forms Nabothian cysts, usually less than about 5 mm (0.20 in) in diameter,[4] which are considered physiological rather than pathological.

[15]: 106 The cervical canal is a pathway through which sperm enter the uterus after being induced by estradiol after penile-vaginal intercourse,[21] and some forms of artificial insemination.

[21] Although the "upsuck theory" has been generally accepted for some years, it has been disputed due to lack of evidence, small sample size, and methodological errors.

Among these changes are several involving the quality of her cervical mucus: the sensation it causes at the vulva, its elasticity (Spinnbarkeit), its transparency, and the presence of ferning.

As the fetus descends within the uterus in preparation for birth, the presenting part, usually the head, rests on and is supported by the cervix.

[32] As labour progresses, the cervix becomes softer and shorter, begins to dilate, and withdraws to face the anterior of the body.

[33] The support the cervix provides to the fetal head starts to give way when the uterus begins its contractions.

During childbirth, the cervix must dilate to a diameter of more than 10 cm (3.9 in) to accommodate the head of the fetus as it descends from the uterus to the vagina.

[34][35] Generally, the active first stage of labour, when the uterine contractions become strong and regular,[34] begins when the cervical dilation is more than 3–5 cm (1.2–2.0 in).

[35] The number of past vaginal deliveries is a strong factor in influencing how rapidly the cervix is able to dilate in labour.

[32] The time taken for the cervix to dilate and efface is one factor used in reporting systems such as the Bishop score, used to recommend whether interventions such as a forceps delivery, induction, or Caesarean section should be used in childbirth.

Cervical diaphragms are reusable, firm-rimmed plastic devices inserted by a woman prior to intercourse that cover the cervix.

[44] The introduction of routine screening has resulted in fewer cases of (and deaths from) cervical cancer, however this has mainly taken place in developed countries.

[50] A LEEP procedure using a heated loop of platinum to excise a patch of cervical tissue was developed by Aurel Babes in 1927.

[44] Instituting and sustaining cytology-based programs in these regions can be difficult, due to the need for trained personnel, equipment and facilities and difficulties in follow-up.

[49] Cervical intraepithelial neoplasia is a possible result of the biopsy and represents dysplastic changes that may eventually progress to invasive cancer.

Inflammation is often investigated through directly visualising the cervix using a speculum, which may appear whiteish due to exudate, and by taking a Pap smear and examining for causal bacteria.

[47][59] Diethylstilbestrol, used from 1938 to 1971 to prevent preterm labour and miscarriage, is also strongly associated with the development of cervical stenosis and other abnormalities in the daughters of the exposed women.

[60] Enlarged folds or ridges of cervical stroma (fibrous tissues) and epithelium constitute a cockscomb cervix.

[47] Cervical ectropion refers to the horizontal overgrowth of the endocervical columnar lining in a one-cell-thick layer over the ectocervix.

[70] In domestic pigs, the cervix contains a series of five interdigitating pads that hold the boar's corkscrew-shaped penis during copulation.

[50] However, there was some variation in word sense among early writers, who used the term to refer to both the cervix and the internal uterine orifice.