Lecture 11 Bone PDF

NORMAL BONE Normal bone is composed of organic matrix and inorganic matrix. The organic matrix includes cells, type 1 collagen (90% of bone protein), glycoproteins, The inorganic matrix includes calcium magnesium, potassium, chloride, sodium, and fluoride. The functions of bone include 1-Structu...

NORMAL BONE Normal bone is composed of organic matrix and inorganic matrix. The organic matrix includes cells, type 1 collagen (90% of bone protein), glycoproteins, The inorganic matrix includes calcium magnesium, potassium, chloride, sodium, and fluoride. The functions of bone include 1-Structural support for the mechanical action of soft tissues, such as the contraction of muscles. 2- Protection of soft organs and tissues, as by the skull(brain),bone marrow. a protective site for specialized tissues such as the blood-forming system (bone marrow), and 3- A mineral reservoir, whereby the endocrine system regulates the level of calcium and phosphate in the circulating body fluids There are 3 cell types: Osteoblasts are responsible for the bone formation Osteocytes are responsible for bone maintenance; they are osteoblasts that have become incorporated in the matrix. Osteoclasts are responsible for bone resorption; HEREDITARY BONE DISORDERS Achondroplasia Long bones are short and thick, leading to dwarfism with short extremities. Cranial and vertebral bones are spared, leading to relatively large head and trunk. Intelligence, life span, and reproductive ability are normal. OSTEOPOROSIS Osteoporosis is decreased bone mass (osteopenia), resulting in thin, fragile bones susceptible to fractur by low- impact -trauma Causes: A- primary cause 1-Postmenopausal 2- Senile (aging) B-secondary to a large variety of causes, including metabolic diseases, Gastrointestinal Disorders, vitamin deficiencies, chronic diseases, and drug exposures(cortico steroid).. Common fracture sites include vertebrae (compression fracture); femoral neck (hip fracture); and distal radius (Colles fracture). Kyphosis and loss of height may result. X-rays show generalized radiolucency of bone (osteopenia). OSTEOMALACIA AND RICKETS Osteomalacia(adult) and rickets (children)are both characterized by decreased mineralization of newly formed bone. They are usually caused by deficiency or abnormal metabolism of vitamin D. OSTEONECROSIS (AVASCULAR NECROSIS) Ischemic necrosis with resultant bone infarction Mechanisms contributing to bone ischemia include Vascular compression or disruption (e.g., after a fracture) Steroid administration Thromboembolic disease Primary vessel disease (e.g., vasculitis) Sickle cell crisis OSTEOMYELITIS Osteomyelitis is defined as inflammation of bone and marrow, with infection. Osteomyelitis can be secondary to systemic infection but more frequently occurs as a primary isolated focus of disease; it can be an acute process or a chronic, debilitating illness. common etiologic agents are pyogenic bacteria and Mycobacterium tuberculosis. OSTEOARTHRITIS Osteoarthritis (OA) (degenerative joint disease) is joint degeneration with loss of articular cartilage, with no to minimal inflammation. It is the most common form of arthritis. Risk increases with age; OA affects at least 1 joint in 80% of people age >70 RHEUMATOID ARTHRITIS Rheumatoid arthritis (RA) is a systemic, chronic, inflammatory disease characterized by progressive arthritis, production of rheumatoid factor, and extra-articular manifestations. It affects females 4x more than men, with highest incidence at ages 20–50. Target RHEUMATOID ARTHRITIS : SYNOIVIAL TISSUE OSTEOARTHRITIS : HAYLINE CARTILAGE