Ovary

The ovary is an important part of the female reproductive system. It is a special organ that makes and releases eggs, called ova. There are two ovaries, one on each side of the body. When an egg is ready, it travels from the ovary through a tube called the oviduct into the uterus, where it may meet with sperm to start a new life.

Ovaries also act like tiny hormone factories. They release hormones that help control the menstrual cycle and play a big role in fertility, which means the ability to have babies. These hormones help the body know when it’s the right time each month for an egg to be released.

Ovaries start developing before a baby is even born and continue to work through many years of a person’s life. They go through different stages from the prenatal period, when a baby is growing inside its mother, all the way until menopause, when a person stops getting their menstrual cycle. Understanding how ovaries work helps us learn about how bodies grow and change.

Structure

Each ovary is a small, whitish organ. It sits on either side of the uterus in a place called the ovarian fossa. This area is bordered by the external iliac artery, the ureter, and the internal iliac artery. The ovaries are about the size of a small almond.

The ovaries have a tough outer layer called the tunica albuginea. Inside, there is an outer part called the cortex and an inner part called the medulla. Each month, one of the ovaries releases an egg. This happens during the menstrual cycle. The egg then moves to the fallopian tube, where it might meet with sperm. The ovaries connect to the uterus through the ovarian ligament and are held in place by other tissues and blood vessels.

Function

At puberty, the ovaries start to make more hormones. These hormones help a girl’s body change and get ready for having a baby. The ovaries also let go of egg cells, which are needed for pregnancy.

The ovaries team up with other body parts to manage these changes. They send out hormones that help control many body actions, like the menstrual cycle. As girls get older, the number of egg cells in the ovaries gets smaller, which is normal as they age.

Clinical significance

Ovarian diseases can change how the body works or how babies are made. Sometimes, a small lump called an ovarian cyst can form if an egg does not leave the ovary properly. Many women have these small cysts and stay healthy. In some cases, a woman might have many small parts in the ovary that don’t grow right, which can change how her body works each month.

Society and culture

Cryopreservation

Keeping ovary tissue safe is a way for women to have children later in life or after treatments for diseases like cancer. Doctors take a small piece of ovary tissue and freeze it. Later, this tissue can help make new eggs, so a woman can become pregnant naturally.

History

Long ago, scientists like Aristotle studied the ovaries and thought they helped make babies. Over time, we learned more about how ovaries work. We found out that ovaries make eggs and that taking them out changes a woman’s body. These discoveries helped us learn more about women’s health today.

Other animals

Birds usually have just one working ovary, the left one, while the other stays small and unused. In mammals, like humans, the ovary works like the male testicle. Both make important body parts and release special chemicals that help the body.

Many animals make far more eggs than humans do. Fish and amphibians can have hundreds or even millions of eggs ready at any time. In birds, reptiles, and some special mammals called monotremes, the eggs are big and change the shape of the ovary when they grow. Some small worms called nematodes can live inside the ovaries of fish and grow very large.

Most animals have two ovaries, but this is not always true. In most birds and platypuses, only the left ovary works, while in some sharks and certain fish, only the right ovary works. In some very old types of fish and a few other fish, there is only one ovary instead of two.

Additional images

• Left ovary

• Ovaries

• Uterus, fallopian tubes, and ovaries

• Right ovary