4.1. Introduction to Cervix
The narrow and lower portion of the Uterus which continues the Uterus with the upper end of Vagina is known as the Cervix (Neck in Latin) of the Uterus. The shape of the Cervix is Cylindrical or conical which projects through the anterior wall of the Vagina.
When inspected by the medical instruments, half of the length of Cervix is visible and the remaining half which is present above the Vagina is not visible by the external scopes as it lies in the Uterus and thus is called as the Cervix uteri.
4.2. Anatomy of Ectocervix
Ectocervix is that part of the Cervix which protrudes into the Vagina and thus is also known as Portio vaginalis. The Ectocervix is about 3 centimeters long and 2.5 centimeters wide, on an average. The surface of the cervix is convex and elliptical and is divided into two lips – The Anterior and Posterior lips.
4.3. External Orifice (Os) of the Cervix
The external opening or orifice of the Uterus is known as the External Os and is also known as the Ostium of Uterus or the External opening of the Cervix. This External Os is a depressed, small and not perfectly but somewhat circular aperture on the vaginal portion of the Cervix which is a rounded opening.
Through this opening, the internal cavity of the Cervix communicates with the cavity of the Vagina.
The External Ostium of the Cervix is bounded by two lips – The Anterior lip and the Posterior lip.
The Anterior lip of External Os of Cervix is short and thick, while the Posterior lip of External Os of Cervix is log and thin. Even then, the anterior lip projects lower than the posterior lip because of the slope and angle of the cervix and thus in normal Anatomical and Physiological conditions, both the lips are in contact of the Posterior Wall of Vagina. Before the first pregnancy, the external Os of Cervix is round in shape when viewed through the Canal of Vagina using a speculum, which after the parturition of the first (Primi-) pregnancy, becomes transverse slit shaped (H Shaped).
4.4. Canal of Cervix – Endocervical Canal
The canal of the cervix is also known as the endocervical canal, cervical canal, cervical canal of uterus, or the cavity of cervix. The canal of Cervix is spindle shaped and flattened antero-posteriorly which forms the neck of the Uterus of the Female Reproductive System.
The Canal of the Cervix serves as a communication channel in between the Vagina and the Uterus via the External orifice and the internal orifice, respectively.
The Cervical Canal wall has two longitudinal ridges; the anterior longitudinal ridge and the posterior ridge. From each of the ridges, numerous columns which are small and oblique give out palmate folds which appear like the branches from the stem of a tree which is known as the arbor vitæ uteri. The folds arising from the longitudinal ridges are arranged in such a manner that they fit in between each other so that the canal is closed.
4.5. Internal (Orifice) Os of the Cervix
The internal opening or orifice of the uterus is known as the internal orifice of the cervix uteri or internal Os. The internal Os is a change in the anatomy of the walls of the lower 1/3rd of the Uterus where there is an interior narrowing of the uterine cavity. It is known as the isthmus which can be observed on the surface of the uterus about midway between the apex and base.
4.6. Crypts of the Cervix
The pockets in the cervix linings are known as the crypts of the Cervix. The function of the crypts of the Cervix is to produce Cervical Fluid. The Crypts also aid in holding the sperms after the initial stage of locomotion into the vagina. The sperms which are on hold are then later moved forwards thus increasing the time span which can be utilized for fertilizing the Ovum after one intercourse.
4.7. Arterial Blood Supply of the Cervix
The arterial or Oxygenated blood supply of the Cervix of the Uterus is accomplished by the Vaginal Artery and the Uterine Artery which arise from the Internal Iliac Arteries with the descend of the arteries along the lateral aspect of the Cervix along the 3 and 9’o clock positions.
4.8. Venous Drainage of the Cervix
The venous drainage is carried out by venules and its tributaries running along the path of the arteries and arterioles and then finally draining into the Hypogastric Venous Plexus.
4.9. Lymphatic Drainage of the Cervix
The Lymphatic drainage of the Cervix is carried out by multiple groups of Lymph nodes and Lymphatic vessels including the common, internal, external iliac nodes, the Obturator lymph nodes and the parametrial nodes.