The cervix (synonyms: neck of the uterus, neck of the uterus) represents the lower portion of the uterus ; below, the cervix borders directly on the upper part of the vagina, while above it continues with the uterine isthmus, representing the junction point between the two structures:
- the vagina is a cylindrical duct that houses the penis during coitus and allows the passage of menstrual fluid and the fetus during delivery
- the uterus welcomes the embryo in its own mucosa (implantation) and supports its development into the fetus and the growth of the latter until the moment of delivery
Through the uterine cervix, capable of undergoing important morpho-functional modifications, the spermatozoa pass (and become active) for fertilization , the menstrual flow and the fetus at the time of delivery. As pregnancy progresses , the uterine cervix represents a precious mechanical support that prevents the fetus from exiting prematurely.
The cervix is also known for its oncogenic risk, being the site of the development of one of the most frequent and feared female cancers : cervical cancer .
- FALLOPIO TUBE
The uterine cervix looks like a cylindrical-conical formation with a length of 2.5-4 centimeters and a diameter of 2 and a half centimeters. Its morphological characteristics, on the other hand, are variable in relation to age and parity (number of children).
Above, through the internal orifice, it communicates with the isthmus (uterine strangulation, more evident in the nullipara), which in turn continues with the cavity of the uterine body representing the junction point between the body and the neck of the uterus. Inferiorly, the cervix communicates with the vagina through the external orifice.
In summary, the cervix is then divided into two zones:
- vaginal portion (or exocervix or ectocervix or exocollus or portio vaginalis or vaginal portion) : it continues above with the endocervix and below with the vaginal mucosa through the external uterine orifice (or external ostium), protruding into the vagina like a tench (portion of the cervix that opens into the vagina)
- supravaginal portion (or endocervix or endocollo or uterine portio or intrauterine portion) : it continues above with the isthmus and the body of the uterus through the internal uterine orifice (or internal ostium), and below with the exocervix
The exocervix and uterine isthmus are joined by the endocervical canal , belonging to the endocervix: it is a canal delimited by the two uterine orifices, internal and external, characterized by some protrusions of the mucous membrane called webbed folds. As shown in the figure, this canal has the shape of a spindle: wider in the middle part and narrower in correspondence with the two uterine orifices, internal and external
Functions Of The Cervix: Physiology
- The glands of the uterine cervix secrete mucus under the influence of female sex hormones . Estrogens , whose peak occurs around ovulation , stimulate the cells to secrete a viscous , transparent and acellular mucus which favors the survival and migration of the spermatozoa; it is precisely in the cervical canal that they acquire the fertilizing capacity (capacitation). Conversely, under the stimulus of progesterone la secrezione mucosa cervicale diviene più densa ed acida, opponendosi al passaggio degli spermatozoi in una cavità uterina non ancora predisposta all’impianto. D’altronde, anche l’orifizio uterino esterno ed il canale endocervicale divengono più ampi in fase pre-ovulatoria, quando il collo uterino è soffice e cedevole, mentre nei soggetti con ipoestrogenismo o nelle fasi di scarsa produzione estrogenica il canale risulta più stretto e poco cedevole
- Il muco secreto dalla cervice uterina possiede normalmente anche proprietà batteriostatiche a difesa sia del canale stesso che degli organi più interni della sfera genitale: corpo dell’utero e tube
- During pregnancy, particularly thick mucous secretions accumulate in the cervical canal, blocking it and creating a protective barrier for the fetus called the mucous plug . This plug is lost shortly before delivery.
- During labor, stimulation and stretching of the cervix induces a release of oxytocin , a hormone secreted by the neurohypophysis that causes the uterus to contract at delivery
Histology: Ectocervix, Endocervix And Squamous-Columnar Junction
- the ectocervix is internally covered by a non-keratinized pluristratified squamous epithelium , devoid of glands (the same that characterizes the vagina), also called squamous epithelium
- the endocervix and the endocervical canal are covered by a monostratified (synonyms: simple) columnar (synonyms: bathyprismatic or cylindrical) epithelium consisting of ciliated cells and mucus-secreting cells, with the presence of endocervical glands or pseudoglands which most closely associate it with the epithelium uterine. For this reason it is also known as glandular epithelium
The two epithelia join at the so-called squamous-columnar junction . In most adult women this transition is not abrupt: the squamocolumnar junction is a zone containing irregular areas of columnar and metaplastic squamous epithelium. The size of this area, detectable after the application of acetic acid, varies from 2 to 15 mm.
The precancerous lesions of the cervix, the so-called CIN (cervical intraepithelial neoplasms) , generally originate in the transformation zone extending in depth for less than 7 mm. The deeper the extent of the lesion, the more serious the condition.
The cervix is non-movable because it is attached to the vagina and bladder by loose connective tissue. The body of the uterus, on the other hand, is mobile, even if these movements are limited by various ligaments