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Bones and Muscles - Description and Types

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The body is truly a miracle design of God. The brain, organs, bones, and muscles all work to keep humans alive. Our lungs keep us breathing, the human brain separates us from being like animals, and we can thank muscles and bones for keeping it all together. The function of bones and muscles are themselves extraordinary.

At birth, babies have a varied number of bones; at least 300 to 350, most of them fuse together as the baby grows into an adult. Once the bones have all fused the number of bones drops to 206, the standard amount adults have. Every single bone has its own task, which varies from being able to support the fingers in the hand, to generate enough blood cells for the body.

The bones make blood cells. Aren't they just like rocks that only help us stand? No, they are not. The endoskeleton is composed of bones and cartilage, and the substance on the inside called bone marrow is actually made of living cells. The hard material around it, called the bone matrix is there to protect the cells inside. On the inside of the bones there is not just one type of cell either, there are three; osteoblasts, osteocytes, and osteoclasts.

Osteoblasts help structure new bone; they come from the bone marrow and work in teams to construct the bone. The new bone they make is called osteoid, made of bone collagen and other proteins. The osteoblasts monitor the calcium and mineral placement and levels. Once a team of osteoblasts has finished filling in a bone cavity, they become flat like paper, and line the surface of the bone. These flat osteoblasts are called lining cells, they control the amount of calcium that goes into and out of the bone.

When constructing new bone, some of the osteoblasts teams turn into osteocytes and get covered by the new bone. They are not singled out because they send out small branches to connect with the other osteocytes. These cells can sense where the cracks or where the wear and tear is on the bone, and help the osteoclasts by showing them where they are needed, so they can dissolve the old bone.

Osteoclasts are cells that come directly from the bone marrow and are somewhat like white blood cells. They are large cells that dissolve into the bone. They break down the old tissue to let the osteoblasts fill in the cavity with osteoid.

In the very center of the bone is a cavity that holds the bone marrow. Bone marrow is an important tissue that holds stem cells that are only inside the larger bones. The stem cells then transform into white and red blood cells, and platelets. They are necessary for immunity to viruses, other harmful diseases, and for circulation of blood. Platelets flow around in the bloodstream searching for small openings in the skin where blood may come out and clot to stop bleeding. The bones that contain marrow are the skull, ribs, pelvis, and femur bones, smaller bones do not require marrow

Bone is not the only material in our body that supports our structure. Cartilage helps take stress off the bones. Cartilage is a tissue in the body made of cells called chondrocytes. Cartilage is strengthened by either collagen or an elastin, depending on the type. The three different types of cartilage are hyaline cartilage, elastic cartilage, and fibro cartilage. The main parts of the body that have cartilage are the ears, nose, ribcage, and some spaces between bones, typically joints.

Hyaline cartilage is found in the nose, throat, and lines the bone in joints. Elastic cartilage is found in the ear and the larynx. This cartilage is more flexible than the other types of cartilage because of its elasticity. Fibro cartilage is the strongest



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