1. Bones

2. 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

3. Types of bones Long bone Short bone Flat bone Irregular bone
Each bone composed of cancellous (spongy) and cortical (compact) bone

4. 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

5. 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

6. 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.

7. 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

8. 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

9. 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

10. Common sites
Usually affects axial skeleton particularly the vertebrae and skull, although the pelvis, femur and tibia are other common sites of disease

11. 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