Your bones comprise a hard outer shell covering a less dense tissue resembling honeycomb. When osteoporosis develops, the outer bone 'shell' becomes thin and weak, and the 'honeycomb' develops larger holes, weakening the bones and increasing the risk of fracture. Serious complications may occur when bones are fractured, particularly in hip fractures. An analogy is often drawn between your bones and a bank. Instead of depositing money, you deposit calcium, and your bones represent the 'account'.
Calcium plays a major role in giving bones their strength.
Each day you make deposits and withdrawals, but you should be saving for your future when you may need to withdraw quite large 'sums' of calcium. Our bones possibly reach their peak strength by our early 20's with a great increase in strength during adolescence. The point at which they reach peak strength is called Peak Bone Mass. It's a very important turning point for your bones because there are two major factors which determine the potential for osteoporosis. At about 35 years, bones slowly start to lose calcium.