Cervix
From Free net encyclopedia
Image:Female anatomy frontal.png
The cervix (from Latin "neck") 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", or "neck of the uterus".
Contents |
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 mucus that prevents infection, however the mucus thins when ovum are ready to be fertilized, allowing spermatazoa to pass through the cervix. Most oral contraceptives increase their effectiveness by not allowing this mucus to thin, therefore blocking spermatazoa from passing even when ovum are ready to be fertilized. Some Natural Family Planning methods rely on observing the qualities of the cervical mucus to determine the periods of fertility and infertility during a woman's cycle. 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 dilates 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 semen in 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 menstruation the cervix stretches open slightly to allow the endometrium to be shed. This stretching is believed to be part of the cramping pain 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 10 cm in diameter to allow the child to pass through.
Cervical cancer
In humans the cervix is associated with cervical cancer, a particular form of cancer which is detectable by cytological study of epidermal cells removed 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 arteries and cardinal ligaments to the parametrial, external iliac, internal iliac, obturator, and presacral lymph nodes. From these pelvic lymph nodes, drainage then proceeds to the paraaortic lymph nodes.
See also
- WikiSaurus:cervix — the WikiSaurus list of synonyms and slang words for the cervix in many languages
| Reproductive system - edit |
|---|
| Female - Cervix | Clitoris | Clitoral hood | Fallopian tubes | Bartholin's glands | G-spot | Hymen | Labium | Mammary glands | Ovaries | Skene's glands | Urethra | Uterus | Vagina | Vulva |
| Male - Urethra | Testes | Scrotum | Spermatic cord | Epididymis | Seminiferous tubules | Sertoli cell | Rete testis | Efferent ducts | Vas deferens | Seminal vesicles | Ejaculatory duct | Penis | Corpus cavernosum | Glans penis | Fundiform ligament | Foreskin | Frenulum | Prostate | Bulbourethral glands |
de:Cervix uteri es:Cérvix fr:Col de l'utérus he:צוואר הרחם lt:Gimdos kaklelis nl:Baarmoederhals ja:子宮頚部 pt:Fórnix simple:Cervix