Sexual Health Reproductive Health Issues The Anatomy of the Uterus By Jennifer Whitlock, RN, MSN, FN Jennifer Whitlock, RN, MSN, FN LinkedIn Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine. Learn about our editorial process Updated on October 31, 2021 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Anita Sadaty, MD Medically reviewed by Anita Sadaty, MD Facebook LinkedIn Twitter Anita Sadaty, MD, is a board-certified obstetrician-gynecologist at North Shore University Hospital and founder of Redefining Health Medical. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Anatomy Function Associated Conditions Tests Frequently Asked Questions The uterus, also known as the womb, is the hollow, pear-shaped organ in the female pelvis in which fertilization of an ovary (egg), implantation of the resulting embryo, and development of a baby take place. It is a muscular organ that both stretches exponentially to accommodate a growing fetus and contracts in order to push a baby out during childbirth. The lining of the uterus, the endometrium, is the source of the blood and tissue shed each month during menstruation. Shidlovski / Getty Images Anatomy Three distinct layers of tissue comprise the uterus: Perimetrium: The outer layer of tissue made of epithelial cellsMyometrium: The middle layer made of smooth muscle tissueEndometrium: The inner lining that builds up over the course of a month and is shed if pregnancy does not occur Shaped like an inverted pear, the uterus sits behind the bladder and in front of the rectum. It has four main sections: Fundus: The broad curved area at the top and widest portion of the organ that connects to the fallopian tubes Corpus: The main part of uterus that starts directly below the level of fallopian tubes and continues downward, becoming increasingly narrower Isthmus: The lower narrow part of the uterus Cervix: The lowest two inches of the uterus. Tubular in shape, the cervix opens into the vagina and dilates (widens) to allow The uterus is supported in the pelvis by the diaphragm, the perineal body, and a collection of ligaments, including the round ligaments. Easing Round Ligament Pain Function The uterus performs multiple important functions in the reproductive cycle, fertility, and childbearing. During a normal menstrual cycle, the endometrial lining of the uterus goes through a process called vascularization during which tiny blood vessels proliferate, leaving the lining thicker and rich with blood in the event the egg released during that cycle is fertilized. If this does not happen, the uterus sheds the lining as a menstrual period. If conception occurs, the fertilized egg (the embryo) burrows into the endometrium from which the maternal portion of the placenta, the decidua basalis, will develop. As a pregnancy progresses, the uterus grows and the muscular walls become thinner, like a balloon being blown up, to accommodate the developing fetus and the protective amniotic fluid produced first by the mother and later by urine and lung secretions of the baby. During pregnancy, the muscular layer of the uterus begins contracting on-and-off in preparation for childbirth. These "practice" contractions, Braxton-Hicks contractions, resemble menstrual cramps; some women don't even notice them. They are not the increasingly powerful and regular contractions that are strong enough to squeeze the baby out of the uterus and into the vagina. What Are Braxton-Hicks Contractions? After a baby is born, the uterus continues to contract in order to expel the placenta. It will continue to contract in the coming weeks to return the uterus to its normal size and to stop the bleeding that occurs in the uterus during childbirth. Associated Conditions The uterus can be subject to any of a number of health issues. The most common uterine conditions include: Endometriosis An estimated 11% of women are affected by endometriosis, a condition in which the tissue of the endometrial lining grows outside of the uterus, causing symptoms that include painful cramps, chronic lower back pain, and pain during or after sex. Less common symptoms of endometriosis include spotting between periods, digestive problems, and infertility. Endometriosis typically is treated with extended-cycle hormonal birth control or an intrauterine device (IUD), though some women respond to complementary and alternative therapies such as acupuncture, chiropractic care, or supplements. The condition often goes away after menopause. Endometriosis Fibroids Uterine fibroids are noncancerous tumors that grow in the muscular tissue of the uterus. Fibroids often do not cause symptoms or require treatment. For some women, however, uterine fibroids lead to heavy periods or pain, symptoms typically treated with over-the-counter pain relievers containing ibuprofen or acetaminophen or hormonal contraception. In severe cases, surgery such as endometrial ablation, myomectomy, or uterine fibroid embolization may be required. What Are Uterine Fibroids? Uterine Polyps Polyps are fingerlike growths that attach to the wall of the uterus. They can range in size from as small as a sesame seed to larger than a golf ball. Many women have polyps without knowing it. When symptoms do occur, they can include irregular periods, heavy bleeding, breakthrough bleeding, and infertility. Uterine polyps carry a small risk of cancer and should be removed with a procedure known as hysteroscopy. Sometimes a dilation and curettage (D and C) is done to remove and biopsy endometrial polyps. Keeping an Eye Out for Asymptomatic Uterine Polyps Tipped Uterus Some women have a retroverted or retroflexed uterus, which means it is in a tipped or tilted position. This anatomical anomaly usually isn't detected unless a woman becomes pregnant, and usually is not an issue. However, some women with a tilted uterus may have a higher risk of miscarriage or experience a pregnancy complication known as uterine incarceration. If that happens, a Caesarean delivery will be necessary. Will Having a Tilted Uterus Increase Your Risk of Miscarriage? Uterine Cancer There are two types of cancers that can affect the uterus: One, uterine sarcoma, is very rare. The other, endometrial cancer, originates in the endometrial lining and is fairly common. It typically occurs after menopause. The primary symptom of endometrial cancer is abnormal vaginal bleeding, which may start as a watery, blood-streaked flow that gradually contains more blood. Abnormal vaginal bleeding is not a normal part of menopause and should be discussed with a gynecologist. Endometrial Cancer: Symptoms, Causes, Diagnosis Tests Tests involving the uterus are used to screen for cancer, diagnose certain diseases and conditions, aid in fertility treatments, and monitor the progress of a pregancy. They include: Pap smear: A test in which cervical cells are collected and analyzed in a lab to look for precancerous and other changes Ultrasound: An imaging test that can be performed intravaginally (using a slender transducer—a wand-like instrument inserted into the vagina) or externally with a transducer applied to the abdomen. Ultrasound uses sound waves to produce images of the uterus, Fallopian tubes, ovaries, and surrounding tissue. In pregnancy, external ultrasound is used to check the baby’s progress. Pelvic X-rays: An imaging test that uses radiation to take pictures of the pelvis. X-rays can be used to check the placement of the uterus and identify masses. Hysteroscopy: An interventional procedure in which a tube is inserted into the cervix to see inside the uterus. Hysterectomy is often used to aid in the removal of fibroids. Frequently Asked Questions What is the average size of a uterus normally and during pregnancy? The uterus is usually the size of an apple but can stretch to the size of a watermelon during pregnancy. There are some conditions that may cause an enlarged uterus such as cancer, fibroids, and polycystic ovary syndrome. What is a prolapsed uterus? Sometimes the pelvic muscles and ligaments become weak over time as women age. When these tissues are weak, the uterus is able to drop down into the vaginal area and sometimes pushes out of the vagina. This is a prolapsed uterus. Who is most at risk of uterine prolapse? Risk factors for uterine prolapse include age, having given birth via vaginal delivery, going through menopause, being White, being overweight, and smoking. Reproductive Health Issues Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 13 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Ameer MA, Fagan SE, Sosa-Stanley JN, et al. Anatomy, abdomen and pelvis, uterus. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. U.S. National Library of Medicine: MedlinePlus. Uterus. NIH: Eunice Kennedy Shriver National Institute of Child Health and Human Development. About menstruation. U.S. Department of Health and Human Services Office on Women's Health: HealthyWoman.gov. Endometriosis. U.S. Department of Health and Human Services Office on Women's Health: HealthyWoman.gov. Uterine fibroids. U.S. National Library of Medicine: MedlinePlus. Endometrial polyps. U.S. Department of Health and Human Services Office on Women's Health: HealthyWoman.gov. Uterine cancer. U.S. National Library of Medicine: MedlinePlus. Pap smear. Mayo Clinic. Fetal ultrasound. U.S. National Library of Medicine: MedlinePlus. Pelvis x-rays. U.S. National Library of Medicine. Hysteroscopy. Kehde BH, van Herendael BJ, Tas B, Jain D, Helsen K, Jochems L. Large uterus: what is the limit for a laparoscopic approach? Autops Case Rep. 2016;6(1):51–56. doi: 10.4322/acr.2016.025 Johns Hopkins Medicine. Uterine prolapse.