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Chapter 44 Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

Chapter 44 Disorders of the Skeletal System: Metabolic and Rheumatic Disorders. Normal Bone Remodeling. Osteoblasts are “bone building” cells They control bone remodeling by: Laying down new bone Secreting a compound (RANK ligand) that controls the osteoclasts , the “bone breaking” cells

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Chapter 44 Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

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  1. Chapter 44Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

  2. Normal Bone Remodeling • Osteoblasts are “bone building” cells • They control bone remodeling by: • Laying down new bone • Secreting a compound (RANK ligand) that controls the osteoclasts, the “bone breaking” cells • Normally, bone formation and breakdown are balanced to: • Replace damaged bone • Maintain the amount and density of bone

  3. Bone Growth • Bone cells and bone marrow cells produce OPG • It blocks the action of RANK ligand • The osteoclasts are not told to function • Bone breakdown decreases • Bones grow

  4. Question Tell whether the following statement is true or false. When osteoblasts work harder than osteoclasts, bones grow.

  5. Answer True Osteoblasts build bone tissue; when they are more active than osteoclasts, bone grows. When osteoclasts work harder than osteoblasts, more bone is broken down.

  6. Discussion How is bone remodeling affected by the following? • Vitamin D? • Mechanical stress? • Calcitonin? • Vitamin C?

  7. Osteopenia and Osteoporosis • Osteopenia • Decreased bone • Osteoporosis • Decreased bone mass • Decreased cancellous (spongy) bone strength

  8. Discussion Why are each of these people prone to osteoporosis? • A postmenopausal woman • A 70-year-old man • A hyperthyroid alcoholic • An Olympic figure skater who takes steroids to reduce joint inflammation • A man with a lung tumor that secretes PTH

  9. Discussion (cont.) • Who would be most helped by the following? • Exercise • Increased Ca2+ and vitamin D in the diet • Estrogen receptor stimulators • Inhibitors of bone resorption

  10. Osteomalacia • Bone is not mineralized properly; it is not rigid • It is caused by: • Insufficient calcium absorption • Insufficient phosphate • It results in: • Bone pain and tenderness • Fractures • Deformities

  11. Rickets • Vitamin D deficiency • Inadequate calcium absorption from diet

  12. Paget Disease • Regions of excessive bone turnover • New bone is disorganized • Deformation and fracture common

  13. Question Which bone disorder is characterized by “soft” bones? • Osteopenia • Osteomyelitis • Rickets • Paget disease

  14. Answer • Rickets Calcium need vitamin D in order to be absorbed. In the case of vitamin D deficiency (rickets), calcium cannot be absorbed, and bones become soft.

  15. Rheumatoid Arthritis • Autoimmune disorder • Antibodies against IgG fragments • Cause inflammation in the joint • Abnormal healing responses lay down granulation tissue (pannus)

  16. Treatment of Rheumatoid Arthritis • NSAIDs • Corticosteroids • Leflunomide • Influximab

  17. Systemic Lupus Erythematosus (SLE) • Autoantibodies include: • Antinuclear antibodies (ANA) • Antibodies against RBCs • Antibodies against platelets • Antibodies against coagulation factors

  18. SLE Can Damage Any Tissue • Arthralgia • Skin lesions (butterfly rash) • Glomerulonephritis • Pleuritis • Pericarditis • Atherosclerosis • CNS inflammations

  19. Question SLE produces antibodies against all but which of the following? • RBCs • WBCs • Platelets • Coagulation factors

  20. Answer • WBCs SLE is an autoimmune disease that results in the production of the following antibodies: antinuclear antibodies, and antibodies against RBCs, platelets, and coagulation factors. WBCs are not affected.

  21. Systemic Sclerosis (Scleroderma) • Collagen deposits in skin and internal organs Spondyloarthropathies • Inflammation at the insertions of tendons and ligaments

  22. Reactive Arthropathies • Sterile joint inflammations caused by previous infection • The joints are not infected at the time of inflammation • Can follow infection with many agents including: • Chlamydia • Pseudomonas • Streptococcus • HIV

  23. Osteoarthritis Syndrome • Degenerative joint disease • Inflammation of the joints often secondary to physical damage • Damaged joint cartilage tries to heal itself • Creating osteophytes or spurs • Cartilage contains more water, less collagen • Cartilage becomes weak, rough, eroded • No longer protects the surface of the bone

  24. Gout Syndrome • Increased serum uric acid • Crystals precipitate in the joint • Inflammation results • Tophi are deposits containing monosodium urate crystals

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