The cervix is the lower, narrow part of the uterus that connects the uterus to the vagina. If you are wondering what the cervix is, think of it as a short, muscular canal that controls what passes between these two organs. It plays a role in menstruation, fertility, pregnancy, and childbirth.
Where is the cervix located?
The cervix sits at the top of the vaginal canal, several inches inside the body. It forms the connection point between the uterus above and the vagina below.
Often described as looking like a small donut, the cervix is a rounded structure with a tiny central opening. Through that opening runs the cervical canal, the narrow passage that links the inside of the uterus to the vagina.
The cervix is part of the broader female reproductive anatomy, which also includes the vagina, uterus, fallopian tubes, and ovaries.
What is the cervix made of?
The cervix is made of firm, muscular tissue with two main parts:
- Ectocervix — the outer part that projects into the vagina. This is the portion a healthcare provider can see during an examination.
- Endocervix — the inner part, lined with glands that produce mucus, running up toward the uterus.
The opening in the center is called the os. The point where the ectocervix and endocervix meet is known as the transformation zone, an area providers pay close attention to during screening.
What does the cervix do?
The cervix has several jobs that change depending on where you are in your menstrual cycle and whether you are pregnant.
Letting fluids and cells move
- Menstruation: The cervix opens slightly to let menstrual blood flow out of the uterus and into the vagina.
- Fertility: It allows sperm to pass up into the uterus toward the fallopian tubes.
Producing cervical mucus
Glands in the endocervix make mucus that shifts in texture and amount across the cycle, influenced by hormones. Around ovulation the mucus becomes thinner and more stretchy, which can make it easier for sperm to travel. At other times it is thicker. This is different from the broader topic of normal vaginal discharge, though the two are related.
Acting as a barrier
The cervix helps keep bacteria and other organisms from moving up into the uterus, offering a degree of protection to the upper reproductive tract.
The cervix in pregnancy and childbirth
The cervix changes substantially during pregnancy:
- During pregnancy: It normally stays firmly closed, helping to keep the pregnancy in place. It also forms a thick mucus plug that seals the cervical canal as an added barrier.
- During labor: The cervix softens, thins (effaces), and opens (dilates) to allow the baby to pass from the uterus into the vagina.
These are major physical processes. Anyone who is pregnant or planning a pregnancy should follow the guidance of their own healthcare provider.
Caring for cervical health
You cannot see your own cervix, but you can take steps to protect it.
General ways to support cervical health include:
- Attending screening when invited, according to local guidelines.
- Considering HPV vaccination, which protects against the virus types most linked to cervical cancer.
- Not smoking, since smoking is associated with higher cervical cancer risk.
How the cervix compares with other anatomy
The cervix is one structure within a larger system. To see how the parts fit together, you can read about female reproductive anatomy and, for comparison, male reproductive anatomy. You can also explore more topics in our body and anatomy education section.
The bottom line
The cervix is the lower part of the uterus that connects it to the vagina, acting as a controlled gateway for menstrual blood, sperm, and, eventually, childbirth. It also helps protect the upper reproductive tract and is the focus of cervical screening, one of the most effective tools for preventing cervical cancer. Understanding what the cervix is and does can help you recognize what is normal and know when to seek care. For personal concerns, always consult a qualified healthcare provider.
