(or neck of the
) is the lower, narrow portion of the uterus
where it joins with the top end of the
. 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
The portion projecting into the vagina is referred to as the
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.
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.
The passageway between the external os and the uterine cavity is
referred to as the endocervical
. 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
The endocervical canal terminates at the internal os
which is the
opening of the cervix inside the uterine cavity.
There are pockets in the lining of the cervix known as cervical
They function to produce cervical fluid.
of the cervix is
varied.The ectocervix (more distal, by the vagina) is composed of
.The endocervix (more proximal, within the
uterus) is composed of simple
The area adjacent to the border of the endocervix and ectocervix is
known as the transformation
. 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
squamous epithelium which is better suited to the vaginal
environment. Similarly when the ectocervix enters the less harsh
uterine area it undergoes metaplasia
become columnar epithelium.
Times in life when this metaplasia
transformation zone occurs:
- puberty; when the endocervix everts (moves out) of the
- with the changes of the cervix associated with the normal
- post-menopause; the uterus shrinks moving the transformation
All these changes are normal and the occurrence is said to be
However, all this metaplasia does increase the risk of cancer in
this area - the transformation zone is the most common area for
cervical cancer to occur.
At certain times of life, the columnar epithelium is replaced by
metaplastic squamous epithelium, and is then known as the
are often found in
After a menstrual period
external os is blocked by mucus
that is thick
and acidic. This "infertile" mucus blocks spermatozoa from entering
. For several days around the time
, "fertile" types of mucus are
produced: they have a higher water content, are less acidic, and
have a ferning pattern that helps guide spermatozoa
through the cervix. This ferning is
a branching pattern seen in the mucus when observed with low
Some methods of fertility
involve estimating a woman's periods of fertility and
infertility by observing changes in her body. Among these changes
are several involving the quality of her cervical mucus: the
sensation it causes at the vulva, its elasticity (spinnbarkeit
), its transparency, and the
presence of ferning
Most methods of hormonal
work primarily by preventing ovulation, but their
effectiveness is increased because they prevent the fertile types
of cervical mucus from being produced. Conversely, methods of
thinning the mucus may help to achieve pregnancy. One suggested
method is to take guaifenesin
in the few
days before ovulation.
During pregnancy the cervix is blocked by a special antibacterial
infection, somewhat similar to its state during the infertile
portion of the menstrual cycle
mucus plug comes out as the cervix dilates in labor or shortly
After menstruation and directly under the influence of estrogen
, the cervix undergoes a series of changes
in position and texture. During most of the menstrual cycle, the
cervix remains firm, like the tip of the nose, and is positioned
low and closed. However, as a woman approaches ovulation, the
cervix becomes softer, and rises and opens in response to the high
levels of estrogen present at ovulation. These changes, accompanied
by the production of fertile types of cervical mucus, support the
survival and movement of sperm.
stretches open slightly to allow the endometrium
to be shed. This stretching is
believed to be part of the cramping
many women experience. Evidence for this is given by the fact that
some women's cramps subside or disappear after their first vaginal
birth 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.
Stimulation of the cervix leads to orgasm for some women. During
, 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 would tend to
draw semen in the vagina
into the uterus, increasing the likelihood of
explanation has been called the "upsuck theory of female orgasm."
Komisaruk, Whipple, and Beyer-Flores, in their book, The Science of
Orgasm, claimed there is evidence in support of the upsuck theory.
Science historian Elisabeth Lloyd
(The Case of the Female Orgasm) has questioned the logic of this
theory and the quality of the experimental data used to back
Short cervix is the strongest predictor of preterm birth
. Some treatments to prevent
cervical cancer, such as LEEP
, cold - Knife cone,
or cryotherapy may shorten the cervix.
infection is a necessary factor in the development of nearly all
cases of cervical cancer. HPV vaccines
can reduce the chance of developing cervical cancer, if
administered before initiation of sexual activity. Potentially
pre-cancerous changes in the cervix can be detected by a Pap smear
, in which epithelial cells
are scraped from the surface of the cervix and examined under a microscope
. With appropriate
treatment of detected abnormalities, cervical cancer can be
prevented. Most cervical cancers occur in women who have never had
a Pap smear, or not had one within the last five years.
Worldwide, cervical cancer is the fifth most deadly cancer in
women. It affects about 16 per 100,000 women per year and kills
about 9 per 100,000 per year. Pap smear screening has greatly
reduced cervical cancer incidence and mortality in nations with
regular screening programs.
The lymphatic drainage
cervix is along the uterine arteries
and cardinal ligaments
to the parametrial,
external iliac vein
, internal iliac vein
, and obturator
and presacral lymph nodes
. From these pelvic lymph nodes,
drainage then proceeds to the paraaortic lymph nodes
. In some women,
the lymphatics drain directly to the paraaortic nodes.
Most women report that stimulation of the cervix during intercourse
is very painful and results
in a sensation similar to being kicked in the stomach
. However, there are reports of women
achieving intense orgasms
as a result of
stimulation of certain parts of the cervix. One area in particular,
a ring-like structure that encircles the cervix, which is said to
have a texture similar to the back of a Frisbee
, has been reported to be highly erogenous
. This area, in a sexual
context, is sometimes referred to as
the Deep spot
(in common with both the AFE zone
and the Rectouterine pouch
) or the
Image:Illu repdt female.jpg|Organs of the female reproductive system.
Image:Illu cervix.jpg|Uterus and uterine tubes.
Image:Gray1167.svg|Posterior half of uterus and upper part of vagina.
Beautiful Cervix—site with a series of photographs illustrating
the cervix over a menstrual cycle