Which Two Minerals Make Bones Strong?
When asked about what makes bones strong, your first thought is probably calcium. And you'd be right. Calcium is one of the two primary minerals that make up bones and contribute to their strength. The second mineral, which is just as important as calcium but less well known, is phosphorous.
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Function of Bones
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Bones serve three functions that require strength. They protect critical organs, they support the body, and together with the muscles, they facilitate movement. They also produce blood cells in the bone marrow and serve as the body's storage system for calcium and phosphorous. The blood must maintain strict levels of calcium and phosphorous so when levels drop, minerals are easily withdrawn from the bones. They're just as easily re-deposited when blood levels get too high. This is important because the nerves and muscles require calcium to function and they rely on a steady supply from the blood.
Bone Formation
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In spite of their strength, bones are not solid, they are actually porous. Depending on the amount of pores present, bone is either spongy (a lot of spaces) or compact (few spaces). Spongy bone provides space for living tissue such as blood vessels to function in the bones. Compact tissue is more dense and stronger, forming the outer covering that bears most of the body's weight. The formation of bones is called ossification and there are two types of ossification: intramembranous and endochondral.
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Intramembranous Ossification
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This is the process that builds flat bones by calcifying fibers of connective tissue. Clusters of cells called osteoblasts secrete collagen fibers that grow together to form a matrix. Then calcium and phosphorous (in the form of calcium phosphate) accumulate on the matrix and harden. As clusters of osteoblasts become surrounded by the calcified matrix, they fuse together to form a latticework. This is spongy bone. Over time, the surface layers of the spongy bone will become compact bone.
Endochondral Ossification
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The word endochondral means "within cartilage." Endochondral ossification is a very complex process in which cartilage becomes calcified as minerals are deposited within the cartilage cells. This causes the cellular components to degenerate, creating spaces similar to spongy bone. Simultaneously, osteoblasts deposit layers of minerals on the outer surface around the cartilage but not at the ends. This allows the cartilage to continue growing at each end, increasing the length of the bone. Between the ages of 18 and 20 the cartilage cells are replaced by bone and growth stops.
Calcium and Phosphorous in the Body
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Calcium is the most abundant mineral in the body. Phosphorous is the second. Most of the phosphorous and calcium are combined together to build bones and teeth but both can also be found circulating independently throughout the body to fulfill other roles. Phosphorous is a critical component in the body's production of energy, it is part of basic cell structure, and it works to maintain a regular heartbeat. Calcium is required for blood clotting and muscle contraction. The overall health of bones depends on the appropriate balance of both minerals. Additionally, the body needs sufficient amounts of vitamins D, K, and C to use calcium.
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