What are the Different Types of Bone Marrow?

Amanda R. Bell

Bone marrow, the flexible tissue found inside the bones of the body and responsible for blood cell creation, comes in two types. Red marrow is made up primarily of hematopoietic tissue, the tissue that makes up blood cells. Fat cells account for almost all yellow marrow.

Three pieces of bone with the marrow in the middle.
Three pieces of bone with the marrow in the middle.

Red bone marrow creates almost all of the body’s blood cells and platelets, with the exception of a few white blood cells known as lymphocytes, which reach maturity in the lymphatic tissues of the body. Red marrow exists most commonly in bones that are flat, such as hip bones, breast bones, the skull, ribs, shoulder blades and the vertebrae of the spine. Red blood cells, which carry oxygen from the lungs to other organs, are essential to keeping the body healthy. Red marrow ensures that the body always has the proper level of blood cells.

A diagram of the anatomy of a bone, showing the bone marrow.
A diagram of the anatomy of a bone, showing the bone marrow.

The main purpose of yellow bone marrow is to store fat. This is the body’s natural way of protecting itself from extreme starvation, because the body will consume the fat in yellow marrow as a last resort. Yellow marrow can also turn itself back into red marrow in cases of severe blood loss or anemia. This transformation can happen in as little as an hour, protecting the body from red blood cell loss and organ damage stemming from a lack of oxygen. This type of marrow is stored in the hollow center of the long bones of the body.

The hip bones contain red bone marrow.
The hip bones contain red bone marrow.

Both types of marrow are prone to certain diseases, especially red marrow. The body’s stem cells are contained primarily in red marrow, so any disease affecting it can dampen the immune system's ability to function. The most common red bone marrow disease is the cancer leukemia, although exposure to chemotherapy or radiation can also damage the stem cells in the marrow. Bone marrow transplants are almost always needed in such cases.

Bone marrow makes up as much as 4 percent of the total body weight of a human. People are born with all red marrow, but the body begins converting it to yellow marrow around age 5 and, by adulthood, nearly half of the marrow in the body is yellow marrow. Red bone marrow is one of the most important parts of the human body, but yellow marrow works as an effective backup if any problems arise with the red marrow.

Almost all blood cells and platelets are created by red bone marrow.
Almost all blood cells and platelets are created by red bone marrow.

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Discussion Comments


So what kinds of diseases affect yellow bone marrow? Can the yellow marrow become cancerous, or does it happen more like leukemia?

Bone marrow transplants aren't necessary for leukemia every time, thank goodness. For the "garden variety," most of the time, chemotherapy, and maybe some radiation will usually cure the disease.

Some hospitals have follow up programs to track the progress of children who have been treated for leukemia, as well as for any problems that might crop up later on as a result of the treatments.


Well, I learned something! I found out there were two types of bone marrow. I didn't know. I thought it was all the same kind. Isn't it amazing to find out what the human body is capable of?

I also had no idea that bone marrow could change form -- and as in little as an hour. That's truly incredible.

I have to say it's equally amazing how someone could read about yellow marrow changing to red and not believe in some kind of intelligent design at work. There has to be a mind behind that kind of action!

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