OSSEOUS SYSTEM
The osseous system consists of the skeleton which forms the bony frame work of the human body the human skeleton consists of approximately 200 individual bones the whole skeleton can be divided into two parts: (1) axial skeleton which includes skull vertebral column ribs and sternum and (2) appendicular skeleton which includes the bones of upper and lower limbs the bones of upper limb are attached to the trunk through scapula (the shoulder bone) and clavicle (the collar bone) while the bones of lower limb are joined through the hip bone
structure and composition of bone ::
A bone is structurally a complex organ it is composed of 25%water 35% organic solids (ossein osseomucoid and osseoalbumin )and 45%inorganic salts of calcium the hardness of bone is because of the presence of calcium salts bone contains one third of organic substances and two third of inorganic substance the organic substances decrease with age whereas the mineral salts increase so that the bones of elderly people are less resilient than those of children
histologically a bone can be divided into two parts compact bone and spongy bone the external part of the compact bone is covered by periosteum it consists of outer fibrous layer and the inner osteogenic layer cambium the function of periosteum are attachment of muscles and tendons covering protection regeneration of bone and healing of fracture the unit of compact bone is haversian system which is made up of haverisan canal haversian lamellae and lacunae the blood vessels nerves and lymphatics are present in this part various cells present in the bone are osteoblasts osteocytes and osteoclasts
the spongy part is found in the inner part of flat bones body of the vertebrae and rounded ends of long bones calcification is less dense here it consists of number of spaces filled with bone marrow the inner lining of marrow cavity is endosteum
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