ASCCP - Practice Recommendations - Practice Management Materials

PRACTICE RECOMMENDATIONS: Practice Management Materials

• Vulva • Vagina • Cervix • Anus

THE CERVIX: Anatomy of the Uterine Cervix

• I.	Introduction	• V.	Invasive Cancer of the Cervix
• II.	Anatomy of the Uterine Cervix	• VI.	Colposcopy
• III.	Histology of the Normal Cervix	• VII:	Cervical Cancer Screening and Colposcopy During Pregnancy
• IV.	Premalignant Lesions of the Cervix		Cervical Cancer Screening and Colposcopy During Pregnancy

SHAPE AND DIMENSIONS
The cervix is actually the lower, narrow portion of the uterus, connected to the uterine fundus by the uterine isthmus. Its name is derived from the Latin word for "neck." It is cylindrical or conical in shape. Its upper limit is considered to be the internal os, which is an anatomically and histologically ill-defined junction of the more muscular uterine fundus and the denser, more fibrous cervical stroma. The cervix protrudes through the upper anterior vaginal wall. Approximately half its length is visible; the remainder lies above the vagina beyond view. The portion projecting into the vagina is referred to as the portio vaginalis. On average, the portio vaginalis is 3 cm long and 2.5 cm wide. The size and shape of the cervix varies widely with age, hormonal state, and parity. In parous women, the cervix is bulkier and the external os, or lowermost opening of the cervix into the vagina, appears wider and more slit-like and gaping than in nulliparous women. Before childbearing, the external os is a small, circular opening at the center of the cervix. The portion of the cervix exterior to the external os is called the ectocervix. The passageway between the external os and the endometrial cavity is referred to as the endocervical canal. Its upper limit is the internal os. 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. The canal itself shows a complex configuration of mucosal folds or plicae. These make cytologic screening and colposcopy of the endocervical tissues technically more difficult and less reliable than for the smoother and more accessible squamous epithelium of the ectocervix.

The overall size and shape of the cervical portio, along with numerous other factors such as parity, location and severity of disease, will influence choice of management and treatment options. Cold knife conization of the cervix can be associated with subsequent adverse pregnancy outcome in some cases, presumably secondary to shortening of the cervix. Although the determinants of obstetrical cervical competence remain enigmatic, the length of the cervix probably plays a role. In addition, an unusually small or large cervix, or one that is difficult to reach due to anatomic variations, may influence whether any needed treatment will take place in an inpatient versus an outpatient setting.

BLOOD SUPPLY
The blood supply of the cervix derives from the internal iliac arteries, which give rise to the uterine arteries. Cervical and vaginal branches of the uterine arteries supply the cervix and upper vagina. There is considerable anatomic variation and anastomoses with vaginal and middle hemorrhoidal arteries. The cervical branches of the uterine arteries generally descend on the lateral aspects of the cervix at 3 and 9 o'clock. The venous drainage of the cervix parallels the arterial supply, eventually emptying into the hypogastric venous plexus.

LYMPHATICS / MUCOSAL IMMUNITY
The lymphatic drainage of the cervix is complex and variable and includes the common, internal, and external iliac nodes, the obturator and parametrial nodes, and numerous other groups as well. The primary route of spread of cervical cancers is through the lymphatics of the pelvis. Radical hysterectomy for invasive cancer of the cervix includes removal of as much of the pelvic lymphatics as possible.

SUPPORT AND INNERVATION
The main support structures of the cervix are the cardinal and uterosacral ligaments. These attach to the lateral and posterior aspects of the cervix above the vagina and extend laterally and posteriorly to the walls of the bony pelvis. The uterosacral ligaments are the conduits of the main nerve supplying to the cervix, derived from the hypogastric plexus. Sensory, sympathetic, and parasympathetic fibers are present in the cervix. Instrumentation of the endocervical canal (dilatation and / or curettage) may result in a vasovagal reaction with reflex bradycardia in some patients. The endocervix also has a plentiful supply of sensory nerve endings, while the ectocervix is relatively lacking in these. This allows procedures such as small cervical biopsies and cryotherapy to be well tolerated in most patients without the use of anesthesia.

REFERENCES
A Manual of Clinical Colposcopy. Thomas M Julian, MD. The Parthenon Publishing Group, NY, 1997. Chapter 2.

Systemic Pathology / Third Edition, Vol. 6, Female Reproductive System. Ed. MC Anderson. Churchill Livingston, London, 1991. p. 47.

Comprehensive Gynecology. Droegemuller W, Herbst AL, Michell Dr, Stendever MA. CV Mosby Co, St Louis, 1987, p. 48-51.