Biology of the Bone
New bone cells, settling in cartilage and beginning to harden.
Bones are living tissue. Just like other organs and tissues within the body, bones need food and oxygen. These nutrients allow bones to do what other living tissues do: break down old tissue and re-grow new tissue.
Wiggle the tip of your nose with your finger. Your nose bends because it is made of a soft material called cartilage.
Before you were born, your whole skeleton was made of cartilage, a flexible type of connective tissue related to bone. As you grew, special cells formed your bones by using the cartilage as a frame; one kind of cell digested the cartilage while another kind of cell replaced it with new bone cells. Blood vessels grew into the new bone, feeding it with oxygen, calcium, and other important nutrients.
Cartilage remains in some parts of your body to give it greater flexibility. It is most easily identifiable in the nose and ears. Try wiggling your kneecap. This part of the body, which feels much firmer than your nose, became hard bone in order to give your knees the strength to support your frame.
How do soft cells become hard bone?
The process of bone renovation!
New cells concentrate where new tissue is needed and release molecules called proteins into their environment. The proteins attract Calcium and other minerals that harden and transform the tissue into solid bone.
This environment outside the cells is called Extra Cellular Matrix, which means structure outside the cell. It is made up of molecules and minerals produced by your body’s cells—mainly proteins like collagen. The Extra Cellular Matrix is what makes your bones strong and hard.
Remember the cartilage in your nose? It is flexible because the cells that make up the tissue have a different Extra Cellular Matrix than bone cells.
The process of bone renovation does not exclusively occur in young bones. This process occurs on an everyday basis. Those special cells that make and re-build bone are at work right now. One type of cell digests old bone material, while another builds newer, healthier bone. Even after you are done growing taller, these cells are constantly renewing your bone so that it remains strong and healthy.
Bones are full of blood, cells, and activity!
Watch the movie to the right to see how bones are richly covered in capillaries. Capillaries are thin blood vessels, and they provide bone cells with oxygen and important nutrients.
At the center of the bone you will also see the red marrow.
The bone marrow is a marvelous factory that produces young cells - stem cells - that have the ability to become new blood, brain, bone, and heart cells. In children all bones contain marrow, but fully-grown adults only have marrow in certain bones, such as their pelvis, skull, ribs, sternum, collarbones, and the ends of other bones.
Bones are always changing- old cells are removed and new cells become bone in the process of bone renovation.