CERVIX CANCER

Schematic frontal view of female anatomy
1: fallopian tube, 2: bladder, 3: pubic bone, 4: g-spot, 5: clitoris, 6: urethra, 7: vagina, 8: ovary, 9: sigmoid colon, 10: uterus, 11: fornix, 12: cervix, 13: rectum, 14: anus
Latin	cervix uteri
Gray's	subject #268 1259
Artery	vaginal artery, uterine artery
Precursor	Müllerian duct
MeSH	Cervix+uteri
Dorlands/Elsevier	cervix uteri

The cervix (or neck of the uterus) is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall. Approximately half its length is visible with appropriate medical equipment; the remainder lies above the vagina beyond view. It is occasionally called "cervix uteri". Cervix means neck in Latin.

Anatomy

Ectocervix

The portion projecting into the vagina is referred to as the portio vaginalis or ectocervix. On average, the ectocervix is 3 cm long and 2.5 cm wide. It has a convex, elliptical surface and is divided into anterior and posterior lips.

External os

The ectocervix's opening is called the external os. The size and shape of the external os and the ectocervix varies widely with age, hormonal state, and whether the woman has had a vaginal birth. In women who have not had a vaginal birth the external os appears as a small, circular opening. In women who have had a vaginal birth, the ectocervix appears bulkier and the external os appears wider, more slit-like and gaping.

Endocervical canal

The passageway between the external os and the uterine cavity is referred to as the endocervical canal. It varies widely in length and width, along with the cervix overall. Flattened anterior to posterior, the endocervical canal measures 7 to 8 mm at its widest in reproductive-aged women.

Internal os

The endocervical canal terminates at the internal os which is the opening of the cervix inside the uterine cavity.

Cervical crypts

There are pockets in the lining of the cervix known as cervical crypts. They function to produce cervical fluid.^[

Histology

The epithelium of the cervix is varied. The ectocervix (more distal, by the vagina) is composed of nonkeratinized stratified squamous epithelium The endocervix (more proximal, within the uterus) is composed of simple columnar epithelium.

The area adjacent to the border of the endocervix and ectocervix is known as the transformation zone. The Transformation zone undergoes metaplasia numerous times during normal life. When the endocervix is exposed to the harsh acidic environment of the vagina it undergoes metaplasia to squamous epithelium which is better suited to the vaginal environment. Similarly when the ectocervix enters the less harsh uterine area it undergoes metaplasia to become columnar epithelium.

Times in life when this metaplasia of the transformation zone occ