BONES HUMAN SKELETON Axial skeleton 80 bones hyoid

BONES

HUMAN SKELETON � Axial skeleton -80 bones (hyoid bone, skull bones, vertebral column and thorax) � Appendicular skeleton -126 bones (upper and lower exptremities, pectoral gridle and pelvic girdle) � Total – 206 bones � Skeleton – 14% of weight of total body

TYPES OF BONES � Long bone � Short bone � Flat bone � Irregular bone Each bone composed of cancellous (spongy) and cortical (compact) bone

� Cancellous bone – found in the ends of long bone and inner layer of the flat bones � Cortical bone – found in shaft of long bone and outer layer of flat bones

LONG BONES Diaphysis � Made of thick cortical bone and contains the medullary cavity where bone marrow is stored � Diaphyseal cavity is composed primarily of fatty tissue and contains yellow marrow � Endosteum is a layer of connective tissue that lines both yellow and red marrow cavity Metaphysis – composed of cancelloes bone

� Epiphysis – composed of spongy tissue and contains red marrow which is responsible for hematopoisesis � Epiphysial plate (cartilaginous plate) separates the metaphysis form the epiphysis in children which merge after puberty.

STRUCTURE OF BONE � Bone is made up of cells, fibers and ground substance with crystallized minerals � Bone is DYNAMIC substance (continuously synthesizing and resorbing bone tissues ) Bone cells � osteoblast, osteocytes and osteoclasts

PAGETS DISEASE- OSTEITIS DEFORMANS � Pagets disease is characterized by an excess of bone destruction and unorganized bone formation and repair. � Second most common metabolic bone disorder

ETIOLOGY � Cause is unknown � Genictc predispositon – 10% of patients � viral infection – triggers the disease � Autoimmune dysfunction � Varcular disorders � Vitamin D deficiency in childhood � Mechanical stressors to bone

COMMON SITES � Usually affects axial skeleton particularly the vertebrae and skull, although the pelvis, femur and tibia are other common sites of disease

PATHOPHYSIOLOGY � Increase in osteoclast mediated resorption of cancellous bone along with an increase in osteoblast mediated bone formation � The new bone is structurally weak and enlarged � Bone resorption and bone formation increases resulting in mosaic like mix of abnormal woven and lamellar bone. � Mineralization