Bones, Muscles and Joints

Bones, muscles, and joints are very crucial parts of our body. Without them, we would not be able to move about.


Bones are our body’s support. Form head to toe, we have bones to support our weight and help form our shape. Our bones also protect the body’s vital organs. The skull protects our brain. It also forms the shape of our face. The spinal cord which is the link that connects the brain and body is protected by the spinal column. The rib cage protects the heart, lungs, liver, and spleen. The pelvis helps protect the bladder, intestines, and in women, the reproductive organ.

The entire human skeleton has 206 bones. Our skeleton starts forming even before birth. Our first skeletal forms are made of flexible cartilage. In a matter of weeks though, it undergoes ossification where the cartilage is replaced by hard deposits of calcium phosphate and collagen. This entire process takes about 20 years.

The bones of kids and teens are small and contain growth plates. These growth plates are made up of columns of multiplying cartilage cells that grow longer and then harden into mineralized bone. Girls’ growth plates change into bone earlier than boys because they mature earlier than boys.

The body continually renews and reshapes itself, thus bone building goes on throughout life.

Bone contains three types of cells:


Osteoblasts make new bone and help repair damage.


Osteocytes transport nutrients and waste products to and from blood vessels in the bone.


Osteoclasts break down bone, then sculpt and shape it.

Inside many of our bones is the bone marrow where most blood cells are made. The bone marrow contains stem cells which produce red blood cells that carry oxygen to the body’s tissues, and platelets that help with blood clotting.

Bone are actually made up of two kinds of bone:

Compact bone

Compact bone is the hard, outer part of the bone. It resembles ivory, is solid, and extremely strong. The compact bone has holes and channels running through it to accommodate blood vessel and nerves from the bone’s membrane covering or periosteum, to the inner parts.

Cancellous bone

Cancellous bone is located inside the compact bone. It resembles a sponge, and is made up of a mesh-like network of tiny fragments of bone called trabeculae. The spaces between each fragment are filled with red and yellow marrow. Red marrow is located mainly at the ends of bones, while yellow marrow is mostly fat.

Bones are attached to other bones by ligaments. Some cartilages do not ossify into hard bone. These can be found in the joints where they support bones and protect them where they rub against each other.