The cervix is somewhat conical in shape, with its truncated apex directed posteriorly and inferiorly. The inferior aspect of the cervix protrudes into the vaginal vault which surrounds it.
The canal of the cervix (endocervical canal) is somewhat fusiform, flattened from anterior to posterior and broader in the middle than at either extremity. It communicates through its internal orifice (internal os) with the cavity of the body of the uterus, and through the external orifice (external os) with the vaginal cavity. The wall of the canal presents an anterior and a posterior longitudinal ridge, from each of which arise a number of small oblique columns, the palmate folds, giving the appearance of branches from the stem of a tree. The folds on the two walls are not exactly opposed but fit between one another so as to close the cervical canal.
Owing to its various attachments, it is less freely movable than the uterine body. In turn, the long axis of the cervix is therefore seldom in the same plane as the long axis of the uterine body.
Musculotendinous and ligamentous
- anterior: pubocervical ligament
- lateral: transverse cervical ligaments (Cardinal or Mackendrodt's) - attached to the side of the cervix uteri and to the vault and lateral fornices of the vagina
- posterior: uterosacral ligaments
- inferior: puborectalis and pubovaginalis parts of the levator ani muscle
The cervix projects through the anterior wall of the vagina, which divides it into an upper, supravaginal portion, and a lower, vaginal portion.
- anterior: separated from the bladder by fibrous tissue (parametrium), which extends also on to its sides and the lateral wall between the layers of the broad ligaments.
- lateral: the uterine arteries reach the margins of the cervix within the broad ligaments, while on either side the ureter runs downward and forward in it at a distance of about 2 cm from the cervix.
- posterior: the supravaginal cervix is covered by peritoneum, which extends below onto the posterior vaginal wall, and then is reflected onto the rectum, forming the rectouterine excavation. It is in close proximity to the rectum, from which it may be separated by coils of the small bowel.
The vaginal portion of the cervix projects frees into the anterior wall of the vagina between the anterior and posterior fornices. On its rounded extremity is a small, depressed external orifice (external os) of the uterus, through which the cavity of the cervix communicates with that of the vagina. The external orifice is bounded by two lips, an anterior and a posterior, of which the anterior is the shorter and thicker, although, on account of the slope of the cervix, it projects lower than the posterior. Normally, both lips are in contact with the posterior vaginal wall.
- arterial supply: a branch of the uterine artery
- venous drainage: drains to the uterine vein, then to the internal iliac vein
- external and internal iliac nodes
- sacral nodes
- cervical branches derived from the inferior hypogastric plexus
- sympathetic: the uterovaginal plexus derived from lower lumbar spinal cord segments
- parasympathetic: the uterovaginal plexus derived from the pelvic splanchnic nerves (S2-4)
In the cervix, the mucous membrane is sharply differentiated from that of the uterine cavity. It is thrown into numerous oblique ridges, which diverge from an anterior and posterior longitudinal raphe. In the upper two-thirds of the canal, the mucous membrane is provided with numerous deep glandular follicles, which secrete a clear viscid alkaline mucus. In addition, extending through the whole length of the canal is a variable number of tiny cysts, presumably follicles which have become occluded and distended with retained secretion known as nabothian cysts.
The mucous membrane covering the lower half of the cervical canal has numerous papillae. The epithelium of the upper two-thirds is cylindrical and ciliated, but below this, it loses its cilia, and gradually changes to stratified squamous epithelium close to the external orifice. On the vaginal surface of the cervix, the epithelium is similar to that lining the vagina (stratified squamous).