Cervix

and part of the vagina. The cervix is the lower part of the uterus situated between the external os (external orifice) and the internal os (internal orifice). The cervical canal connects the interior of the vagina and the cavity of the body of the uterus.|alt=Diagram of the uterus and part of the vagina. The cervix is part of the female reproductive system. Around in length, and the mucosa covering the ectocervix is known as the exocervix. The cervix has an inner mucosal layer, a thick layer of smooth muscle, and posteriorly the supravaginal portion has a serosal covering consisting of connective tissue and overlying peritoneum. 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. The cervical canal varies greatly in length and width between women or throughout a woman's life, On average, the ectocervix is long and wide. and drains into the uterine vein. Visceral pain from the supravaginal portion of the cervix is transmitted via afferent fibers that travel with sympathetic nerves to spinal cord levels T10-L1 through the inferior hypogastric and uterovaginal plexuses. The vaginal portion of the cervix receives somatic sensory innervation via branches of the pudendal nerve (S2-S4). Parasympathetic fibers arising form the pelvic splanchnic nerves (S2-S4) contribute autonomic input via the inferior hypogastric plexus. The anterior and lateral cervix drains to nodes along the uterine arteries, travelling along the cardinal ligaments at the base of the broad ligament to the external iliac lymph nodes and ultimately the paraaortic lymph nodes. The posterior and lateral cervix drains along the uterine arteries to the internal iliac lymph nodes and ultimately the paraaortic lymph nodes, and the posterior section of the cervix drains to the obturator and presacral lymph nodes. These changes are also accompanied by changes in cervical mucus, The cervix grows in size at a smaller rate than the body of the uterus, so the relative size of the cervix over time decreases, decreasing from being much larger than the body of the uterus in fetal life, twice as large during childhood, and decreasing to its adult size, smaller than the uterus, after puberty. 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. Histology , visible as the darker red mucosa surrounding the cervical os. Viewed on speculum exam. The endocervical mucosa is about thick and lined with a single layer of columnar mucous cells. It contains numerous tubular mucous glands, which empty viscous alkaline mucus into the lumen. Underlying both types of epithelium is a tough layer of collagen. The mucosa of the endocervix is not shed during menstruation. The cervix has more fibrous tissue, including collagen and elastin, than the rest of the uterus.Type 1: Completely ectocervical (common under hormonal influence).Type 2: Endocervical component but fully visible (common before puberty).Type 3: Endocervical component, not fully visible (common after menopause). In prepubertal girls, the functional squamocolumnar junction is just within the cervical canal. After menopause, the uterine structures involute, and the functional squamocolumnar junction moves into the cervical canal. Nabothian cysts (or Nabothian follicles) form in the transformation zone where the lining of metaplastic epithelium has replaced mucous epithelium and caused a strangulation of the outlet of some of the mucous glands. A buildup of mucus in the glands forms Nabothian cysts, usually less than about in diameter, which are considered physiological rather than pathological. Both gland openings and Nabothian cysts are helpful to identify the transformation zone. == Function ==

Fertility The cervical canal is a pathway through which sperm enter the uterus after being induced by estradiol after penile-vaginal intercourse, and some forms of artificial insemination. Some sperm remains in cervical crypts, infoldings of the endocervix, which act as a reservoir, releasing sperm over several hours and maximising the chances of fertilisation. A theory states the cervical and uterine contractions during orgasm draw semen into the uterus. Some methods of fertility awareness, such as the Creighton model and the Billings method involve estimating a woman's periods of fertility and infertility by observing physiological changes in her body. 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. in the endocervix produce 20–60 mg of cervical mucus a day, increasing to 600 mg around the time of ovulation. The viscosity and water content vary during the menstrual cycle; cervical mucus is composed of around 93% water, reaching 98% at midcycle. It contains electrolytes such as calcium, sodium, and potassium; organic components such as glucose, amino acids, and soluble proteins; trace elements including zinc, copper, iron, manganese, and selenium; free fatty acids; enzymes such as amylase; and prostaglandins. Its consistency is determined by the influence of the hormones estrogen and progesterone. In the follicular phase of the menstrual cycle, estrogen dominates and cervical mucus gradually becomes thinner, reaching its lowest viscosity at ovulation. At midcycle, around the time of ovulation—a period of high estrogen levels— the mucus is thin and serous to allow sperm to enter the uterus and is more alkaline and, hence, more hospitable to sperm. At other times in the cycle, the mucus is thick and more acidic due to the effects of progesterone. Women taking an oral contraceptive pill also have thick mucus from the effects of progesterone. A cervical mucus plug, called the operculum, forms inside the cervical canal during pregnancy. This provides a protective seal for the uterus against the entry of pathogens and leakage of uterine fluids. The mucus plug is also known to have antibacterial properties. This plug is released as the cervix dilates, either during the first stage of childbirth or shortly before. It is visible as a blood-tinged mucous discharge. Childbirth to release oxytocin (4). Oxytocin is carried in the bloodstream to the uterus, causing contractions to induce childbirth. The cervix plays a major role in childbirth. 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. Generally, the active first stage of labour, when the uterine contractions become strong and regular, The second phase of labor begins when the cervix has dilated to , which is regarded as its fullest dilation, and is when active pushing and contractions push the baby along the birth canal leading to the birth of the baby. Contraception Several methods of contraception involve the cervix. Cervical diaphragms are reusable, firm-rimmed plastic devices inserted by a woman before intercourse that cover the cervix. Pressure against the walls of the vagina maintains the position of the diaphragm, and it acts as a physical barrier to prevent the entry of sperm into the uterus, preventing fertilisation. Cervical caps are a similar method, although they are smaller and adhere to the cervix by suction. Diaphragms and caps are often used in conjunction with spermicides. In one year, 12% of women using the diaphragm will undergo an unintended pregnancy, and with optimal use this falls to 6%. Efficacy rates are lower for the cap, with 18% of women undergoing an unintended pregnancy, and 10–13% with optimal use. Most types of progestogen-only pills are effective as a contraceptive because they thicken cervical mucus, making it difficult for sperm to pass along the cervical canal. In addition, they may also sometimes prevent ovulation. ==Clinical significance==

Cancer In 2008, cervical cancer was the third-most common cancer in women worldwide, with rates varying geographically from less than one to more than 50 cases per 100,000 women. It is a leading cause of cancer-related death in poor countries, where delayed diagnosis leading to poor outcomes is common. The introduction of routine screening has resulted in fewer cases of (and deaths from) cervical cancer; this has mainly taken place in developed countries. Most developing countries have limited or no screening, and 85% of the global burden occurs there. Cervical cancer nearly always involves human papillomavirus (HPV) infection. HPV vaccines, such as Gardasil and Cervarix, reduce the incidence of cervical cancer, by inoculating against the viral strains involved in cancer development. Potentially precancerous changes in the cervix can be detected by cervical screening, using methods including a Pap smear (also called a cervical smear), in which epithelial cells are scraped from the surface of the cervix and examined under a microscope. In some parts of the developed world, including the UK, the Pap test has been superseded with liquid-based cytology. An inexpensive, cost-effective, and practical alternative in poorer countries is visual inspection with acetic acid (VIA). A result of dysplasia is usually further investigated, such as by taking a cone biopsy, which may also remove the cancerous lesion. Most cases of cervical cancer are detected in this way, without having caused any symptoms. When symptoms occur, they may include vaginal bleeding, discharge, or discomfort. Inflammation Inflammation of the cervix is referred to as cervicitis. This inflammation may be of the endocervix or ectocervix. When associated with the endocervix, it is associated with a mucous vaginal discharge and sexually transmitted infections such as chlamydia and gonorrhoea. Other causes include overgrowth of the commensal flora of the vagina. When associated with the ectocervix, inflammation may be caused by the herpes simplex virus. 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. Special tests may be used to identify particular bacteria. If the inflammation is due to a bacterium, then antibiotics may be given as treatment. Anatomical abnormalities Cervical stenosis is an abnormally narrow cervical canal, typically associated with trauma caused by removal of tissue for investigation or treatment of cancer, or cervical cancer itself. 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. Other abnormalities include: vaginal adenosis, in which the squamous epithelium of the ectocervix becomes columnar; cancers such as clear cell adenocarcinomas; cervical ridges and hoods; and development of a cockscomb cervix appearance, Enlarged folds or ridges of cervical stroma (fibrous tissues) and epithelium constitute a cockscomb cervix. Similarly, cockscomb polyps lining the cervix are usually considered or grouped into the same overarching description. It is in and of itself considered a benign abnormality; its presence, however, is usually indicative of DES exposure, and as such, women who experience these abnormalities should be aware of their increased risk of associated pathologies. Cervical agenesis is a rare congenital condition in which the cervix completely fails to develop, often associated with the concurrent failure of the vagina to develop. Other congenital cervical abnormalities exist, often associated with abnormalities of the vagina and uterus. The cervix may be duplicated in situations such as bicornuate uterus and uterine didelphys. Cervical polyps, which are benign overgrowths of endocervical tissue, if present, may cause bleeding, or a benign overgrowth may be present in the cervical canal. Cervical ectropion refers to the horizontal overgrowth of the endocervical columnar lining in a one-cell-thick layer over the ectocervix. ==Animals==

Female marsupials have paired uteri and cervices. Most eutherian (placental) mammal species have a single cervix and a single, bipartite or bicornuate uterus. Lagomorphs, rodents, aardvarks, and hyraxes have a duplex uterus and two cervices. Lagomorphs and rodents share many morphological characteristics and are grouped in the clade Glires. Anteaters of the family Myrmecophagidae are unusual in that they lack a defined cervix; they are thought to have lost the characteristic, rather than other mammals developing a cervix on more than one lineage. In domestic pigs, the cervix contains a series of five interdigitating pads that hold the boar's corkscrew-shaped penis during copulation. ==Etymology and pronunciation==

The word cervix () came to English from Latin , which means "neck". Like its English translation, the Latin word can refer not only to the neck [of the body], but also to an analogous narrowed part of an object. Thus, the term (literally "neck of the uterus") is used in Latin to refer to the uterine cervix, but in English, the word cervix used alone usually refers to it. The first attested use of the word in English to refer to the cervix of the uterus was in 1702. The adjective cervical may refer either to the neck (as in cervical vertebrae or cervical lymph nodes) or to the uterine cervix (as in cervical cap or cervical cancer). The Latin word was in turn used to translate the Greek word (), "neck". The cervix was documented in anatomical literature in at least the time of Hippocrates; cervical cancer was first described more than 2,000 years ago, with descriptions provided by both Hippocrates and Aretaeus. Greek writers usually used the term () to refer to the cervical canal; however, there was some variation in the sense of these two words. == References ==