The central canal consists of nerve fibers and small blood vessels. These different directions of collagen fibers (anisotrophy) enable bone to resist torsion strength. The lamella consists of collagen with each different direction. ![]() An osteon consists of layers of lamella around the central canal. The cylinder form is orientated parallel to the long axis of the bone. Osteon in cortical bone called Haversian systems and are cylindrical in shape. Both cortical and trabecular bone are composed of osteons. 1,2,4 Spongy bone has a porosity of 30% to more than 90% 3 due to bone marrow intertrabecular and vascular space. However, in spongy bone the trabeculae are aligned along the stress lines and it helps bones to resist stress. Cancellous bone, also spongy bone, is present in de epiphysis and metaphysis of long bones. Compact bone looks like solid bone, however it has a porosity of 5 to 30% 3 due to osteons canals. ![]() Compact bone is dense and solid and found in the external bone surface and in the walls of the bone shaft. 1-3 All bones consist of two different types of bone, compact bone and cancellous bone. ![]() Irregular bones include hipbones and vertebrae, these bones are complicated in shapes and not fit in the other classes. Most of the skull bones and ribs are a bit curved, flattened and thin. Short bones are cube shaped like the wrist and the ankle. Long bones consist of epiphyses, the ends of the bone, and its diaphysis, the shaft of the bone. The femur and ulnae are examples of long bones. 1-2 Bones are classified in long bones, short bones, flat bones and irregular bones.
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