Cervix Function and Anatomy

The cervix is the lower portion (or the "neck") of the uterus. It is approximately 1 inch long and 1 inch wide and opens into the vagina. The cervix functions as the entrance for sperm to enter the uterus. During menstruation, the cervix opens slightly to allow menstrual blood to flow out of the uterus.

Cervix Functions

Your cervix has several important functions, including:

• Producing cervical mucus during the most fertile phase of the menstrual cycle, which helps sperm travel from the vagina into the uterus
• Opening during labor to allow the baby to pass through the birth canal
• Protecting the uterus from bacteria and other foreign objects

Here is how the cervix functions during specific phases of the menstrual cycle and pregnancy:

During Menstruation 

During menstruation, the cervix opens a small amount to permit the passage of menstrual blood out of the uterus and through the vagina.

During Conception

Conception occurs when sperm travel through the cervix to enter the uterus and ultimately fertilize an egg. Around ovulation, the most fertile part of the menstrual cycle, your cervix produces clear mucus, which helps the sperm reach the uterus.

During Pregnancy and Labor

During pregnancy, cervical mucus thickens to create a cervical "plug" that shields the growing embryo from infection.

When a woman gets closer to going into labor, the cervical plug thins and is expelled. The cervix softens and shortens (this is called effacement) and then dilates in preparation for birth.

As your due date nears, your healthcare provider will check the cervix for dilation to try to gauge when you are likely to give birth.

During Menopause 

During menopause, hormonal changes and aging change the nature of the cervical mucus and vaginal discharge. As a result, some menopausal women experience vaginal dryness.

Where Is the Cervix?

The cervix is located between the uterus and the vagina. It's possible to feel the cervix with your finger; if you do so, you'll notice that it changes texture over the course of your cycle. In order to actually see your cervix, you will need to use a mirror and a bright light, but it may still be difficult to see based on the length of your vagina.

The narrow opening of the cervix is called the os. The cervical os allows menstrual blood to flow out from the vagina during menstruation.

There are three parts of the cervix:

1. The lowest part, which can be seen from inside the vagina during a gynecological exam, is called the ectocervix. The center of the ectocervix can open, creating a passage between the uterus and vagina.
2. The highest part is the endocervix, also called the endocervical canal. It's the passage between the ectocervix and the uterus.
3. The point in the middle where the endocervix and ectocervix meet is called the transformation zone.

The cervix is covered by the epithelium, which is made of a thin layer of cells. Epithelial cells are either squamous or columnar (also called glandular cells). Squamous cells are flat and scaly, while columnar cells are, as their name suggests, column-like.

Conditions and Problems

The cervix is prone to certain conditions and diseases, including:

• Cervical cancer: Most cases of cervical cancer are caused by human papillomavirus (HPV), a sexually transmitted infection (STI) that can lead to cervical cancer. The Centers for Disease Control and Prevention suggest that all children be vaccinated against HPV at ages 11 to 12, but some people can be vaccinated up to age 45.
• Cervicitis: Cervicitis occurs when the the cervix becomes inflamed, sometimes as the result of a sexually transmitted infection such as chlamydia, gonorrhea, or herpes.
• Cervical dysplasia: This is the term for abnormal cells in the cervix that can develop into cervical cancer. Cervical dysplasia may be discovered with a Pap test.
• Cervical polyps: These are small growths on the ectocervix. Polyps are painless and usually harmless, but they can cause vaginal bleeding.
• Cervical insufficiency: Also called incompetent cervix, this occurs when the cervix is too weak to maintain a pregnancy, potentially leading to a miscarriage.

In some cases, the cervix is surgically removed along with the uterus to treat cancer or certain other conditions. This is called a total hysterectomy.

A Word From Verywell

It's helpful to know how your cervix functions, as it plays an important role in conception, menstruation, and childbirth. Talk to your gynecologist about how you can maintain a healthy cervix with regular Pap smears, safe sex (to avoid STIs), and getting the HPV vaccine.