What is Bone Marrow?

Article Details
  • Originally Written By: S. Mithra
  • Revised By: Andrew Jones
  • Edited By: L. S. Wynn
  • Last Modified Date: 14 May 2020
  • Copyright Protected:
    Conjecture Corporation
  • Print this Article
External Resources
Free Widgets for your Site/Blog
In 2015, Japan recorded 2,310 compensation claims for illnesses and deaths caused by “karoshi,” or overwork.  more...

May 31 ,  1929 :  The Ford Motor Company signed a deal with the USSR.  more...

Bone marrow is a distinctive class of tissue that fills the cores of larger bones in humans and other animals. Unlike the hard, or compact, tissue that forms the outer shells of bones, the marrow has a malleable, sponge-like texture. It serves an active function in the body by producing all three types of blood cells, as well as lymphocytes, which support the immune system. Transplants are frequently performed in patients whose own marrow has become diseased. Additionally, marrow is a major source of stem cells, which can be harvested for certain medical treatments. Rich in nutrients, bone marrow even makes a highly desirable food source for animals as well as for humans in numerous cultures.

Bones that Contain Marrow

In humans, marrow is found in the interior of most major bones of the body. These include flat bones such as the sternum, skull, and pelvis, as well as most long bones, such as the humerus and the femur. Other smaller bones, by contrast, like those in the spine and lower jaw, contain little or no marrow. Marrow is referred to as a spongy bone. It's infused with blood vessels that supply oxygen and carry away newly created cells.

Types of Marrow

There are two categories of bone marrow: yellow and red. The yellow type mostly contains fat, and serves to provide sustenance and maintain the correct environment for the bone to function. It tends to be located in the center-most cavities of long bones, and is generally surrounded by a layer of red marrow. Red marrow is directly involved in cell production. As a body ages, the quantity of red marrow tends to shrink while the amount of yellow marrow increases, but it tends to have the strongest concentrations in flat bones such as the sternum or ilium.


Immature stem cells, along with extra iron, can be found inside bone marrow. These stem cells wait until weak, unhealthy, or damaged cells need to be replaced, and then differentiate, or become specialized. An undifferentiated stem cell can, for example, turn into a red or white blood cell or a platelet. Likewise, lymphocytes, part of the lymphatic system, are formed in this way. This is how such cells get replaced to keep the body healthy, making healthy bone marrow tissue crucial in fighting pathogens like fungi, bacteria, and viruses.

A number of diseases, often incurable, pose a threat to bone marrow. Put simply, they prevent it from turning stem cells into essential cells. Leukemia, Hodgkin's Disease, and other lymphoma cancers are known to damage the marrow's productive ability and destroy stem cells.

Bone Marrow Transplants and Stem Cell Harvesting

The leading treatment for conditions that threaten the marrow's ability to function is a bone marrow transplant. This procedure typically begins with chemotherapy to eliminate the compromised marrow. A matching donor must then be found; in most cases, this is a close family member. A needle is usually used to extract the donor's red marrow, often from one of the pelvic bones. The red marrow is then injected into the patient's bloodstream. With luck, the donation will "take," and make its way into the central shaft of larger bones to restore stem cell function.

Through a similar procedure, stem cells themselves can be harvested for certain cancer treatments, as well as for ongoing medical research into other potential medical uses. Stem cells may either be directly extracted, in the same way as they are for bone marrow transplants, or medication can be given that stimulates the marrow to release the cells into the bloodstream. In the latter case, after blood is drawn from the donor, the stem cells are then filtered out.

As a Food Source

The high concentration of fat, as well as minerals including iron, make bone marrow an eagerly sought food source. Many species of animals chew on large bones of their prey, even after the meat is gone, in order to crack them open and gain access to the treat held within. Likewise, it is considered a delicacy in a variety of human cultures around the world, ranging from parts of Europe to Asia and the Americas.

You might also Like


Discuss this Article

Post 22

@anon942777: People who have a bone marrow transplant and the donors for the one who is getting the BMT are not paralyzed. The donor is sore for a few days to a week, but that is it. The only reason why I know this is because I had a bone marrow transplant for ALL. This is a type of leukemia called Acute Lymphocytic Leukemia.

Post 21

After a bone marrow transplant, is the donor paralyzed?

Post 20

bone marrow cancer is not something any one should joke about. i take it very personally! my mother got sick with it at the age of 32 and died at the age of 37 with it. people should have a little more respect for things!

Post 14

That's so wrong even to joke about. What if someone was dumb enough to actually try that? Does this relate to bone marrow?

Post 11

Bone marrow is harmful more than cancer and its treatment is as expensive as transplant. the other treatment is given through injections but that is not reliable.

Post 10

"4: Try it from a high building, Einstein - anon22431"

That's so wrong even to joke about. What if someone was dumb enough to actually try that?

Post 9

now it is true that you can levitate or fly by magnetizing the iron in you nervous system. i've tried it.

Post 8

Well anon1741 if you could levitate or fly by magnetizing the iron in your nervous system without destoying the nervous system itself you could, quite possibly, and with a powerful enough magnitized force, be able to fly. But those are all pretty big if's.

Post 6

The bone marrow is the red blood cells, the fatty part, and stem cells, right? But what part of a bone marrow transplant is used from the marrow? The fat, the blood and/or only the stem cells?

Post 4

Try it from a high building, Einstein

Post 1

I was wondering how much iron can be stored in bones. i'm a physicist and a runner. i discovered some equations that say you can condense all the laws of physics into 8 words. If copper is high, molybdenum is low, iron. i was wondering if i had a strong enough electrical current because of my nervous system if i could magnetize all the stores of iron in my bones. if i can control the nervous current with my brain could one produce enough force to levitate or fly?

Post your comments

Post Anonymously


forgot password?