What is a Sacrum? - Definition, Location & Function

Instructor: Justine Fritzel

Justine has been a Registered Nurse for 10 years and has a Bachelor's of Science in Nursing degree.

The sacrum is part of your spine. In this lesson we will learn more about the sacrum. We will learn what it is, where it is located, and what functions it serves.

The Backbone of your Body

Your skeletal system is responsible for holding up your body and protecting your internal organs. If you did not have a skeletal system you would be like a jelly fish!

Your spine is essential in supporting your upper body. The spine is made up of vertebrae which are small donut shaped bones that are stacked to form our spine. Starting at the top of your spine, at the base of your skull, begins your seven cervical vertebrae. Continuing down your spine begins your twelve thoracic vertebrae followed by five lumbar vertebrae. After the lumbar vertebrae is the sacrum and then your coccyx, or tailbone.

Here is a picture of entire spinal column that we just talked about. Let's learn more about the sacrum next.


What is the Sacrum?

The sacrum is a wedge-shaped bone that is below the fifth lumbar vertebrae at the base of your spine. It is made up of five vertebrae that begin to fuse into one single bone when you are in your late teens or early twenties.


Did you know that the word 'sacrum' means 'sacred' in Latin? Many cultures believe this bone is holy! It protects the precious organs that create life. It is also usually the last bone to rot when buried. There was belief that because of that, the body could reassemble around the sacrum in the afterlife.

The first three vertebrae of the sacrum have small bony pieces that extend off the sides that are called alae. The alae connect with the large bones of the pelvis called ilium. Where the sacrum connects to the ilium is called the sacroiliac joint. The sacrum has four openings on each side that allows nerves and blood vessels to pass through.

Now that you understand more about the sacrum, you may be wondering what is the function of the sacrum.

Does the Sacrum serve any Purpose?

As we discussed previously, the sacrum connects to the hip bones and is important in forming a strong pelvis. The sacrum provides support at the base of your spine. The sacrum is a very strong bone that helps to support the weight of the upper body. In fact, it's so strong that it is seldom fractured. It takes a severe injury such as a fall to fracture the sacrum, although someone with osteoporosis is at risk of stress fractures in the sacrum.

Sacroiliac Joint

There are also several muscles that connect to the sacrum. These muscles pull on the sacrum to allow the leg to move. Without the sacrum, most activity wouldn't be possible, including walking, running, and climbing.

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