The skeletal system is made up of all the bones in an organism’s body. The human body, for example, has 206 bones. The skeleton serves many important and diverse purposes. Not only does the skeleton determine the shape of and provide support for the body, but it’s also involved in maintaining mineral homeostasis, storing minerals, anchoring muscles, facilitating movement, producing blood cells, and protecting important organs, such as the heart and the lungs. Despite its importance and apparent rigidity, bones, like all organs in the body, are susceptible to disease and injury, including fractures, osteoarthritis, and rickets.
Skeletal System: The organ system that consists of the bones, cartilage, and ligaments.
Cartilage: Flexible connective tissue.
Ligament: Fibrous connective tissue.
Joint: Where two bones meet.
Bone Matrix: Framework of bones, made up of protein fibers, such as collagen, and minerals, such as calcium.
Collagen: A protein found commonly in connective tissue.
Compact Bone: Dense and hard outer shell of most bone. Gives bone the stiff quality that allows it to protect the body’s organs and generally support the body.
Spongy Bone : Porous and relatively soft inner layer of bone.
Bone Marrow: Tissue in the inner pores of spongy bone that produces new blood cells.
Periosteum: A membrane covering the outside of bone.
Osteoblast: Specialized bone cell that gives rise to new bone cells, playing a key role in bone growth. Osteoblasts also secrete the collagen found in the bone matrix and contribute to mineral uptake.
Osteoclast: Specialized bone cell responsible for the release of minerals into the blood.
Osteocyte: Specialized bone cell involved in regulating mineral uptake and release.
Ossification: The process by which connective tissue, including cartilage, turns into bone.
The skeletal system can be divided into the axial skeleton and the appendicular skeleton.
Image Credit: Mariana Ruiz Villarreal (LadyofHats), Public Domain
Image Credit: Mariana Ruiz Villarreal (LadyofHats), Public Domain
The joint is one region where we can find cartilage and ligament. The cartilage provides a smooth surface for the bones to move, and the ligament connects bones together. Joints can be categorized by function and the degree of movement they permit
Although bones appear to be unchanging, bones are actually living tissues that are constantly being reshaped.
The bone matrix forms the rigid framework of bones.
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Bones are made up of different types of tissues. In addition to compact bone and spongy bone, bone also contains bone marrow and periosteum.
The three types of specialized bone cells are osteoblasts,
osteocytes, and osteoclasts. They are responsible for bone growth and mineral homeostasis.
The skeleton of a human fetus is made entirely of cartilage. The soft cartilage turns into the hard bone that we are familiar with through ossification. The mineral deposits stored in the bone replace the cartilage. When we are young, ossification occurs at the center of the bone and continues toward the two ends of the bone. This allows the bone to continue to grow longer. When all the cartilage has been replaced, the bone can no longer grow longer and growth stops.
Bones, like any organ in the body, are susceptible to damage and disease. Three common problems that plague bones are below: