The uterine cervix (synonyms: cervix, cervix) represents the lower portion of the uterus ; at the bottom, the cervix borders directly with the upper part of the vagina, while at the top it continues with the uterine isthmus, representing the junction between the two structures:
- the vagina is a cylindrical duct that welcomes the penisduring coitus and allows the passage of menstrual flow and the fetus during childbirth
- the uterus receives the embryoin its own mucosa (implant) and supports its development into the fetus and its growth up to the moment of delivery
Through the uterine cervix, capable of undergoing important morpho-functional modifications, the spermatozoa pass (and become active) for fertilization , menstrual flow and the fetus at birth. With the evolution of pregnancy , the cervix represents a precious mechanical support that prevents the premature exit of the fetus.
The cervix is also known for its oncogenic risk, as it is the site of the development of one of the most frequent and feared female cancers : cervical cancer .
|4) FALLOPIUM TUBE|
The uterine cervix appears as a cylindro-conical formation with a length of 2.5-4 centimeters and a diameter of 2.5 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 constriction, 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 cervix. Inferiorly, the cervix communicates with the vagina through the external orifice.
In summary, the cervix is then divided into two zones:
- vaginalportion (or exocervix or ectocervix or exocollo 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 muzzle of tench (part of the neck of the uterus that flows into the vagina)
- supravaginal portion (or endocervix or endocollo or uterine portio or intrauterine portion): it continues superiorly with the isthmus and the body of the uterus through the internal uterine orifice (or internal ostium), and at the bottom with the exocervix
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 mucosa called palmate folds. As shown in the figure, this canal has the shape of a spindle: wider in the middle part and narrowed in correspondence of the two uterine orifices, internal and external
Functions of the Cervix: Physiology
- The glands of the uterine cervix secrete mucusunder the influence of female sex hormones . The estrogens , whose peak occurs in the vicinity of ‘ ovulation , stimulate cells to secrete a viscous mucus, transparent and acellular that promotes the survival and migration of the spermatozoa; it is precisely in the cervical canal that they acquire the fertilizing capacity (capacitation). Conversely, under the stimulation of progesteronethe cervical mucous secretion becomes denser and more acidic, opposing the passage of spermatozoa into a uterine cavity not yet predisposed to implantation. On the other hand, also the external uterine orifice and the endocervical canal become wider in the pre-ovulatory phase, when the uterine neck is soft and yielding, while in subjects with hypoestrogenism or in the phases of low estrogen production the canal is narrower and not very yielding
- The mucus secreted by the uterine cervix normally also possesses bacteriostatic properties to defend both the canal itself and the innermost organs of the genital sphere: the body of the uterus and tubas
- During pregnancy, particularly thick mucous secretions accumulate in the cervical canal, obstructing it and creating a protective barrier for the fetus called a mucous plug. This cork is lost shortly before delivery.
- During labor, stimulation and stretching of the cervix induce a release of oxytocin, a hormone secreted by the neurohypophysis that causes the uterus to contract at the time of delivery
Histology: exocervix, endocervix and squamo-columnar junction
From the histological point of view:
- the exocervix is internally covered by a multi-layered, non-keratinized, glandless epithelium (the same that characterizes the vagina), also called squamous epithelium
- the endocervix and the endocervical canal are covered by a monostratified epithelium (synonyms: simple) columnar (synonyms: batiprismatic or cylindrical)consisting of hair cells and mucus secreting cells, with the presence of endocervical glands or pseudoglands that most closely associate it with the epithelium uterine. For this reason it is also known as the glandular epithelium
The two epithelia join in the so – called squamous-columnar junction . In most adult women this transition is not abrupt: the squamocolonnar junction is an area containing irregular areas of columnar and squamous metaplastic epithelium. The size of this area, which can be seen after applying acetic acid, varies from 2 to 15 millimeters.
Precancerous lesions of the cervix, the so-called CIN (cervical intraepithelial neopiasias) , generally originate in the transformation zone extending in depth for less than 7 mm. The deeper the extent of the injury, the more serious the condition.
The cervix is not mobile because it is fixed 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