The uterus is an organ of the female reproductive system. It’s shaped like an upside-down pear and has thick walls. The uterus’s main function is to house and nourish a fetus until it’s ready for birth.

The uterus sits in the middle of the pelvis, behind the bladder and in front of the rectum. The actual position of the uterus within the pelvis varies from person to person. Each position has its own name:

Both of these positions are normal, and the position of the uterus can change throughout a woman’s life, most frequently after a pregnancy.

Fundus

The fundus is the upper part of the uterus. It’s broad and curved. The fallopian tubes attach to the uterus just below the fundus.

Corpus

The corpus is the main body of the uterus. It’s very muscular and can stretch to accommodate a developing fetus. During labor, the muscular walls of the corpus contract to help push the baby through the cervix and vagina.

The corpus is lined by a mucus membrane called the endometrium. This membrane responds to reproductive hormones by changing its thickness during each menstrual cycle. If an egg is fertilized, it attaches to the endometrium. If no fertilization occurs, the endometrium sheds its outer layer of cells, which are released during menstruation.

Isthmus

The portion of the uterus between the corpus and the cervix is called the isthmus. This is where the walls of the uterus begin to narrow toward the cervix.

Cervix

The cervix is the lowest part of the uterus. It’s lined with a smooth mucous membrane and connects the uterus to the vagina. Glands in the cervical lining usually produce a thick mucus. However, during ovulation, this becomes thinner to allow sperm to easily pass into the uterus.

The cervix has three main parts:

  • Endocervix. This is the inner part of the cervix that leads to the uterus.
  • Cervical canal. The cervical canal links the uterus to the vagina.
  • Exocervix. The exocervix is the outer part of the cervix that protrudes into the vagina.

During childbirth, the cervix dilates (widens) to allow the baby to pass through the birth canal.

Use this interactive 3-D diagram to explore the uterus.

Congenital uterine conditions

The word congenital refers to something that a person is born with. According to March of Dimes, about are born with a congenital uterine condition. In some cases, congenital uterine conditions cause pregnancy complications.

Some examples of congenital uterine conditions are:

  • Septate uterus. A band of muscle divides the uterus into two separate sections.
  • Bicornuate uterus. The uterus has two smaller cavities instead of one large one.
  • Didelphic uterus. The uterus has two smaller cavities, each with its own cervix.
  • Unicornuate uterus. Only half of the uterus forms.

Endometriosis

Endometriosis happens when the endometrium, which usually lines the uterus, grows on the outside of the uterus, fallopian tubes, or pelvic lining. It can cause severe pain, especially during menstruation or intercourse.

Uterine fibroids

Uterine fibroids are noncancerous growths on the walls of the uterus. They can range in size from very small (the size of a seed) to quite large (the size of an orange). While fibroids don’t always cause symptoms, some women experience bleeding and pain. In addition, larger ones can also lead to fertility issues in some cases.

Uterine prolapse

A prolapse happens when an organ’s support system is stretched or damaged. Uterine prolapse happens when part of the uterus slips down into the vagina. In severe cases, part of the uterus can stick out of the vaginal opening. Many things can cause this, including childbirth, surgery, menopause, or extreme physical activities.

Pelvic inflammatory disease

Pelvic inflammatory disease (PID) is an infection within the female reproductive organs. It’s sometimes caused by the same bacteria that cause gonorrhea and chlamydia, though other bacteria can also cause it.

The main symptoms of PID are lower abdominal pain, as well as pain during intercourse and urination. Other possible symptoms include unusual vaginal discharge, fatigue, and irregular bleeding. If left untreated, PID can cause infertility and an increased risk of an ectopic pregnancy.

Cancer

While uterine cancer can start anywhere in the uterus, it’s in the endometrium. Several things can increase a woman’s risk of developing endometrial cancer, including obesity and taking estrogen without progesterone.

Cancer can also affect the cells of the cervix, causing cervical cancer. Doctors aren’t sure about the exact causes and risk factors for cervical cancer, but smoking and having sexually transmitted infections both seem to be a factor, in addition to having a weak immune system.

The symptoms of many uterine conditions share some main symptoms, including:

  • very heavy periods
  • bleeding between periods
  • unusual or foul-smelling vaginal discharge
  • pelvic or lower-back pain
  • pain during menstruation or intercourse
  • pain during urination or bowel movements

Contact your doctor if you notice any of these symptoms. Using your medical history and physical exam, they can help to narrow down what might be causing them.

The uterus is an important organ with many moving parts. Follow these tips to keep it healthy:

Get routine Pap smears

Pap smears can detect precancerous changes in your cervix in addition to other uterine conditions. The American Cancer Society :

  • all women aged 21 through 29 have a Pap smear done every three years
  • women who are 30 or older get a Pap smear, along with a human papilloma virus (HPV) test, every five years until the age of 65, even if they’ve been vaccinated against HPV
  • women over 65 stop having Pap smears if they’ve had regular ones for the previous 10 years, unless they have a higher risk of uterine cancer

Get vaccinated against HPV

The HPV vaccine protects against nine strains. It’s available to females between the ages of 9 and 26. According to the FDA, the vaccine can prevent up to of cervical, vaginal, and anal cancers.

Use a condom

Using a condom during intercourse helps to prevent the spread of STIs, which can increase a woman’s risk of developing PID or cervical cancer.

Avoid smoking

Smoking is to certain types of cervical cancer. If you currently smoke, try these tips for quitting.

Eat well

The following types of food are known to help keep your cervix healthy and to boost your immune system:

  • foods rich in folic acid, such as asparagus, broccoli, and other green vegetables
  • foods rich in vitamin C, such as oranges and grapefruits
  • foods rich in beta carotene, such as carrots, squash, and cantaloupe
  • foods rich in vitamin E, such as whole-grain breads and cereals