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Ovaries: What to Know

Medically Reviewed by Dany Paul Baby, MD on October 04, 2022

Sexual reproduction keeps many species alive. In humans, male and female reproductive systems look very different, though. The female reproductive system has many unique parts, including the ovaries, all working in tandem to achieve reproduction.

What Are the Ovaries?

Ovaries are a part of the female reproductive system, as well as the endocrine system.

The female reproductive system is made up of many parts that are both inside the body and on the outside. Ovaries are part of the internal female reproductive system. Other internal components of the female reproductive system include the:

  • Fallopian tubes. The fallopian tubes carry egg cells from the ovaries to the uterus. Fertilization of an egg cell by sperm typically occurs inside the fallopian tubes. The fertilized egg is then carried to the uterus. Ectopic pregnancies, which happen when the egg implants somewhere other than the uterus, most often happen inside the fallopian tubes instead. These pregnancies cannot be carried to term.
  • Uterus. The uterus is made up of two parts: the corpus and the cervix. The corpus is the main section of the uterus. This is where the baby will grow during pregnancy. The cervix is the lower part that creates a separation between the vagina and the rest of the uterus. The cervix contains an opening that allows sperm in and also expels blood and tissue out during a menstrual cycle. When you go into labor, the cervix expands to allow your baby to pass through. 
  • Vagina. The vagina is a muscular canal that connects the uterus to the outside of the body.

What Do the Ovaries Do?

The ovaries have two primary jobs: to make, store, and release female sex hormones and to generate, store, and release eggs.

Making, storing, and releasing ovary hormones. Your ovaries produce two types of hormone: estrogen and progesterone.

Estrogen is an important hormone for both sexes, though less is produced by males. In addition to the ovaries, the adrenal glands and body fat can also secrete estrogen. 

Non-reproductive uses of estrogen in the body include managing:

  • Blood flow and circulation
  • Blood sugar
  • Bone mass
  • Brain function
  • Collagen production
  • Cholesterol

As a reproductive hormone, estrogen also has the following jobs:

  • Changing the body during puberty
  • Releasing eggs during ovulation
  • Increasing fertility
  • Making intercourse more comfortable
  • Regulating the menstrual cycle
  • Stimulating menopause

Progesterone is another important hormone. Its levels rise in the second half of your menstrual cycle to prepare the uterus for a possible pregnancy. It does this by causing the uterine line to thicken so the egg can implant and also by prohibiting uterine muscle contractions. 

If you get pregnant, progesterone levels will remain elevated throughout your pregnancy to stop the body from producing additional eggs and to help prepare the breasts for milk production. If you don’t get pregnant, the levels of progesterone in your body will drop until your next cycle.

Making, storing, and releasing eggs. Those with ovaries are born with all the eggs they will ever have. That means that while a baby is in the uterus, the ovaries are already busy making eggs. These immature eggs are stored within the ovaries in small sacs called the ovarian follicles. Each of your ovaries has thousands of follicles.

Your ovaries release these eggs according to the pattern of your menstrual cycle. Your menstrual cycle has three phases: the follicular phase, the ovulatory phase, and the luteal phase.

The follicular phase is the phase before the ovary releases the egg. The first day of the follicular phase is the first day of your menstrual cycle. During the beginning of this phase, your pituitary gland releases follicle-stimulating hormone (FSH). This stimulates multiple ovarian follicles to begin maturing. As the levels of FSH begin to drop, usually only one follicle continues to mature. This follicle releases estrogen, and estrogen levels rise.

During the ovulatory phase, your pituitary gland sends out a surge of luteinizing hormones and follicle-stimulating hormones. This causes the ovaries to release the egg they’ve been preparing. This process is called ovulation and usually happens midway through your menstrual cycle, at about day 14 or so. The egg passes through the ovarian wall and is caught by the fibers of the fallopian tube.

During the luteal phase, the ruptured ovarian follicle forms a cyst called the corpus luteum. This cyst produces progesterone to prepare the uterus for a possible pregnancy.

Where Are the Ovaries Located?

Your ovaries sit on either side of your uterus. They’re held in place by muscles and ligaments. They’re typically egg-sized but shrink after menopause.

Ovary Conditions and Disorders

Many conditions and disorders may affect the ovaries, causing pain, nausea, and fertility problems. 

Ovarian conditions may include:

  • Ovarian cancer.
  • Endometriosis. Endometriosis is a condition in which uterine-like tissue grows outside the uterus. It can grow on your ovaries or fallopian tubes and in the pelvis. This causes irritation, cysts, and a buildup of scar tissue.
  • Ovarian cysts. Ovarian cysts develop when these fluid-filled sacs grow on the uterus. They are usually harmless but sometimes can become cancerous. Additionally, some may cause severe pain and bleeding if they rupture.
  • Ovarian tumors. Ovarian tumors may grow on the surface lining of the ovaries (i.e., surface epithelial tumors), in the area that produces hormones (stromal tumors), and in the egg cells (germ cell tumors). Most ovarian tumors are benign, but some may be cancerous.
  • Pelvic inflammatory disease (PID). Pelvic inflammatory disease is a condition in which one or more of the female reproductive organs become infected. This is usually caused by sexually transmitted bacteria.
  • Polycystic ovary syndrome (PCOS). PCOS is a condition in which cysts grow along the outer edge of the ovary. These cysts contain egg cells, making them ovarian follicles, but they do not regularly release eggs. PCOS is the result of a hormonal issue that remains somewhat mysterious. 
  • Primary ovarian insufficiency. Primary ovarian insufficiency, also known as premature ovarian failure, happens when the ovaries stop working before a person has reached age 40. This is usually due to an issue with the ovarian follicles. Many things can cause problems with the follicles, including genetic disorders, metabolic disorders, autoimmune diseases, radiation, or toxins like cigarette smoke and pesticides. 

Ovary pain can coincide with ovulation. While severe abdominal pain could be the result of many things, check with your doctor, as it may also be a symptom of a problem with your ovaries.

Show Sources

SOURCES:
American Cancer Society: “What Is Ovarian Cancer?”
Cleveland Clinic: “Endocrine System,” “Estrogen,” “Female Reproductive System,” “Ovaries,” “Pituitary Gland.”
Dignity Health: “Ovarian Tumors.”
Endocrine Society: “Reproductive Hormones.”
Mayo Clinic: “Ectopic pregnancy,” “Endometriosis,” “Pelvic inflammatory disease (PID).”
Medline Plus: “Primary Ovarian Insufficiency.”
Merck Manual: “Menstrual Cycle,” “Polycystic ovary syndrome (PCOS).”
Office on Women's Health: “Ovarian cysts.”

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