What is the Sternum?

D.M. Abrecht

The sternum, also known as the breastbone, is the bone located in the center of the chest where the upper ribs converge. It protects the heart and lungs from injury and helps to stabilize the structure of the ribcage. It is found in most vertebrates — exceptions include fish, snakes, and turtles. It takes different forms in different species; the information in this article pertains to the form it takes in humans.

The xiphoid process lies at the base of the sternum.
The xiphoid process lies at the base of the sternum.

In the human embryo, the sternum first appears as two bands of cartilage which fuse in the center of the chest. This fused band gives rise to six bones, called sternabrae, that gradually combine to become the adult breastbone. The process continues throughout childhood, and may not be complete until middle or even old age. Fusion begins at the top of the bone and proceeds downward.

The sternum connects each side of the rib cage.
The sternum connects each side of the rib cage.

A long, flat bone shaped like the letter "T," the sternum is comprised of three parts. The first sternabra becomes the manubrium, the top part of the bone which forms the horizontal stroke of the "T." The manubrium is roughly diamond-shaped. It is wider at the top, where it connects to the collarbone, and narrower at the bottom.

CPR, performed incorrectly, can injure the sternum.
CPR, performed incorrectly, can injure the sternum.

The next four sternabrae form the middle and longest portion, called the sternal body or gladiolus. This piece forms most of the vertical stroke of the "T." The gladiolus is marked by three horizontal ridges on its front and back surfaces. It connects to the first seven pairs of ribs in humans.

Turtles are one of the few vertebrates that have no sternum.
Turtles are one of the few vertebrates that have no sternum.

A small piece called the xiphoid process connects to the bottom of the gladiolus and completes the bone. It is formed from the last sternabra and is usually the last piece to fuse. In some adults it never becomes fully fused, remaining attached to the rest of the bone by a piece of cartilage. It is thin, long, and occasionally bifurcated.

Accidental injuries to the sternum are rare. When they do occur, they are most often a result of blunt force trauma, as in an automobile accident. Fracture is usually associated with damage to the heart, lungs, and other organs. Incorrectly performed CPR sometimes causes the xiphoid process to break off, which may result in damage to the diaphragm.

In order to perform surgery on organs in the chest cavity, it is often necessary to deliberately fracture the sternum. The procedure is called a median sternotomy. It involves cutting the bone from top to bottom with an oscillating saw and then pulling the two halves apart. After surgery, the bone will heal over the course of several weeks, just like any other broken bone.

A sternotomy is a thoracic surgery that cuts through the sternum, and is often necessary for reaching the heart or lungs.
A sternotomy is a thoracic surgery that cuts through the sternum, and is often necessary for reaching the heart or lungs.

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Discussion Comments


Has anyone been told they have a tight feeling in the sternum? I was told this by my consultant last week. How can they tell you have that? I have had pains there but I never have told anyone. Can anyone give me some info and could it be serious in any way? --genniemi


@cloudel – For years, I had no sternum problems, but after I turned thirty, I started feeling pain like you are describing. My ribcage was tender, and the sudden stabbing was really alarming.

My doctor tested me for heart problems, but I seemed to be fine in that area. She decided that I must have fibromyalgia.

Fibromyalgia can cause the cartilage connecting the sternum to the ribs to become inflamed. This is the reason for all the pain with sudden movements and persistent tenderness.

My doctor told me that the pain should disappear in a few months. She told me I could take ibuprofen when it was really intense, but she advised against taking it all the time, because it could cause organ damage.


I've been having some concerning pains in the area of my sternum. I am in good health, and my blood pressure is perfect, so I don't believe the pains are heart-related.

Sometimes, when I take a deep breath, my chest hurts. If I touch my ribs, they feel sore. If I shift my torso quickly to the side, I feel a sudden stabbing pain.

My mother thinks it is just gas, but I don't believe that. What would gas be doing in my sternum, anyway?

Does anyone have any idea what might be wrong with me? Have you had similar pains, and did you find out what caused them?


I imagine that having your sternum sawed in two would take awhile to recover from! That sounds pretty extreme, but so is heart surgery.

I'm sure that people who have to have heart transplants must have their sternums sawed open. It seems like there would be a lot of pain after the patient wakes up and for quite some time thereafter.

I've never damaged my sternum in any way, but having something so central to your structure cut apart must generate a lot of discomfort. It would probably feel like your very heart was hurting, since it is right over the top of the heart.

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