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Cervix

Image:Female anatomy frontal.png

The cervix (from Latin"neck") is actually the lower, narrow portion of the uteruswhere 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", or "neck of the uterus".

Inhaltsverzeichnis

1 Anatomy
- 1.1 Ectocervix
  - 1.1.1 External Os
- 1.2 Endocervical Canal
- 1.3 Internal Os
2 Cervical Mucus
3 Functionality
4 Cervical cancer
5 Lymphatic Drainage
6 See also

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 Mucus

Normally the external os is blocked by a thick mucusthat prevents infection, however the mucus thins when ovumare ready to be fertilized, allowing spermatazoato pass through the cervix. Most oral contraceptivesincrease their effectiveness by not allowing this mucus to thin, therefore blocking spermatazoa from passing even when ovum are ready to be fertilized. During pregnancy the cervix is completely blocked by a special antibacterial mucosal plug which prevents infection as before. The mucous plug comes out as the cervix dialates in labor or shortly before.

Functionality

During orgasm, the cervix convulses and the external os dilates. Dr. R. Robin Baker and Dr. Mark A. Bellis, both at the University of Manchester, first proposed that this behavior worked in such a way as to draw any semenin the vagina into the uterus, increasing the likelihood of conception. Later researchers, most notably Elisabeth A. Lloyd, have questioned the logic of this theory and the quality of the experimental data used to back it.

During menstruationthe cervix stretches open slightly to allow the endometriumto be shed. This stretching is believed to be part of the crampingpain that many women experience. Evidence for this is given by the fact that some women's cramps subside or disappear after their first baby because the cervical opening has widened.

During childbirth, contractions of the uterus will dilate the cervix up to 10cm in diameter to allow the child to pass through.

Cervical cancer

In humans the cervix is associated with cervical cancer, a particular form of cancerwhich is detectable by cytologicalstudy of epidermalcellsremoved from the cervix in a process known as the pap smear. Evidence now shows that those with exposure to HPV, or the Human Papilloma Virus are at increased risk for cervical cancer. This virus is related to the virus that causes warts.

Lymphatic Drainage

The lymphatic drainage of the cervix is along the uterine arteriesand cardinal ligamentsto the parametrial, external iliac, internal iliac, obturator, and presacral lymph nodes. From these pelvic lymph nodes, drainage then proceeds to the paraaortic lymph nodes.