What Are Human Bones Composed Of?

The human body consists of 206 bones that are made up of several components. The materials that make up human bones are alive and growing, and almost all of the bones in the human body are made of the same components, regardless of where they are in the body.

Periosteum

• The periosteum is the outer membrane that protects the bone and contains the blood vessels that nourish it and help it grow. The periosteum also contains nerves. The outer layer of the membrane is primarily made up of collagen. The inside layer of the periosteum contains osteoblasts, which are cells that produce new bone. The inner layer is most prominent in fetuses and children with rapidly growing bones.

Compact Bone

• Compact bone is the part of the bone most people think of when they see a human skeleton. Compact bone is smooth and hard and makes up 75 to 80 percent of the body’s bone. Compact bone gives the body support. The bone is made up of osteocytes, or mature bone cells, that surround canals running through the bone. The canals are filled with blood vessels to nourish the bone and nerves.

Cancellous Bone

• Cancellous bone is found inside compact bone. It is a spongy tissue that is strong, but not as hard as compact bone. Cancellous bone makes up the remaining 20 to 25 percent of bone in the human body and provides lightweight support for the compact bone. Long bones, such as the femur and the spine contain the most cancellous bone.

Bone Marrow

• Bone marrow is found in the innermost part of the bone. It is protected by the spongy material of the cancellous bone, which creates a barrier between the marrow and the compact bone. Bone marrow does not appear hard or bone-like at all. It has a jelly-type consistency. Red bone marrow creates new red blood cells. The femur and humerus contain the majority of the red bone marrow in the human body. Yellow bone marrow is stored fat. Yellow marrow can turn into red bone marrow in extremely anemic people who are in dire need of more red blood cells.