Histology, Periosteum And Endosteum

Bone is a specialized complex, living connective tissue that supports the body and protects vital organs of the body. Impregnation of the extracellular matrix with the inorganic salts like calcium phosphate and carbonate provides hardness to the bone.Types of Bones: Histologically, bones categorize into two types (1) cortical or compact bone and (2) cancellous bone or spongy bone.Compact Bone (IMAGE 1): The shaft of the long bone like femur has a cavity known as a bone marrow cavity; the cavity is walled by dense material. The dense material is of uniform smooth texture without any cavity within is known as the compact bone. Compact bone slowly changes according to the stress, tension, and other mechanical forces.Cancellous bone: The ends of the long bones are devoid of the marrow cavity. Instead, they are populated with mesh-like structure made up of plates and rods; it contains numerous minute spaces. The structure gives a sponge-like appearance, so this type of bone is known as cancellous or spongy bone. Spongy bone has a larger surface area and a high metabolic rate.Bone is a vascular structure and has a nervous supply also. The outer covering of the bone is known as the periosteum; the periosteum covers the whole surface of the bone except at the ligament attachment, tendon attachment, and an area covered by articulating cartilage. The periosteum is absent in sesamoid bones.A membrane lining the wall of the bone marrow cavity is known as the endosteum.