The strength and rigidity of the bone is a result of the inorganic salts deposited in the matrix. Matrix is basically just large amount of non-cellular materials, which is what your bones are made of.
calcium
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What extra bones ?
There is no extra bone. You remove 6 bones from the three sets of bones to make the letters T-E-N in bones. Remove three, leaving two to make the T. Remove one, leaving four to make the E. Remove two, leaving three to make the N.
Calcium
Bones are made up of calcium, phsophorus, sodium, protein, callagen and other minerals so yes sodium is needed to make bones hard.
Most bird bones are very light, because extra weight would make it impossible to fly.
soft you can bend and hard you can not
Seal's bones are hard.
Mineral salts from calcium and phosphorus compounds are essential for making bones hard and strong. calcium is the most essential mineral to make bones strong but not all bones are as hard as you think some bones are "Spongy" but we just dont notice it. hope this helps if you need to know this....
To make your knuckles hard, you should consider doing things that strengthen your bones. There's no other way to get hard knuckles in your hands, however.
Calcium is used in the body to make the bones hard and strong.