DISEASE OF THE MUSCULOSKELETAL SYSTEM FUNCTIONS BONES. Determines body size and shape. Mechanical support for movement. Protect vital organs

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1 DISEASE OF THE MUSCULOSKELETAL SYSTEM Thanisa Sanmanee, M.D. FUNCTIONS Determines body size and shape Mechanical support for movement Protect vital organs Mineral homeostasis Contain the hematopoietic elements Source:wikimedia BONES

2 CELL TYPES Osteoblasts synthesize Osteocytes mineral homeostasis Osteoclasts resorption Woven bone - random weave, fetal skeleton and the base of growth plates. Lamellar bone - in an orderly layered manner designated, gradually replaces woven bone during growth, stronger than woven bone CELL TYPES ENCHONDRAL OSSIFICATION

3 Robbins, Stanley L, Vinay Kumar, and Ramzi S Cotran. Robbins And Cotran Pathologic Basis Of Disease. 1st ed. Philadelphia, PA: Saunders/Elsevier, Print. Reserve zone Zone of proliferation Zone of hypertrophy Zone of mineralization Primary spongiosa INTRAMEMBRANOUS OSSIFICATION BONE TYPES Cancellous bone 20% bone weight Spongy, flexible Compact bone 80% bone weight Forms cortex of most bones Dense, hard and strong Long bone

4 BONE MATRIX Organic component 40% of dry weight Inorganic component 60% of dry weight ORGANIC COMPONENT Collagen 90% of organic component primarily type I collagen provides tensile strength Proteoglycans responsible for compressive strength inhibit mineralization composed of glycosaminoglycan-protein complexes INORGANIC COMPONENT Matrix proteins noncollagenous proteins promote mineralization and bone formation Calcium hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) provides compressive strength Osteocalcium phosphate (brushite) Cytokine and growth factors aid in bone cell differentiation, activation, growth, and turnover

5 DISORDERS OF THE BONE Growth & Development Achondroplasia Osteogenesis imperfecta Mineralization & Remodeling Osteomalacia/Rickets Osteoporosis ACHONDROPLASIA most common disease of the epiphyseal plate (chondroblasts in proliferating cartilage) major cause of dwarfism autosomal dominant disorder mutation in the FGF receptor 3 (FGFR3) FGFR3 inhibits cartilage proliferation OSTEOGENESIS IMPERFECTA deficiency in the synthesis of type 1 collagen(osteoblasts) most common inherited disorder of connective tissue autosomal dominant mutations (over 800+) causes fragile bones, fractures, short stature

6 DENTINOGENESIS IMPERFECTA opalescent teeth or brittle teeth misshapen, chip or break easily normal enamel, but the DEJ and the dentin are not normal Source: webmd.com OSTEOMALACIA vitamin D deficiency defect in bone mineralization causes soft bone and short stature

7 BONE TUMORS Bone forming Osteoma Osteoid Osteoma Osteoblastoma Osteosarcoma Cartilage forming Osteochondroma Chondroma Chondroblastoma Chondrosarcoma Robbins, Stanley L, Vinay Kumar, and Ramzi S Cotran. Robbins And Cotran Pathologic Basis Of Disease. 1st ed. Philadelphia, PA: Saunders/Elsevier, Print. JOINTS Movement and mechanical stability Classified as solid (nonsynovial) and cavitated (synovial) Solid joints/synarthroses structural integrity, minimal movement Synovial joints wide range of motion lined with hyaline cartilage

8 ARTHRITIS Non-inflammatory joint disease Osteoarthritis Inflammatory joint disease Rheumatoid arthritis Seronegative spondyloarthropathy Ankylosing spondyloarthritis Reiter Syndrome Crystal-induced arthropathy Gout and gouty arthritis RHEUMATOID ARTHRITIS chronic systemic inflammatory disorder women>men triggered by exposure of a genetically susceptible host to an arthritogenic antigen chronic joint pain and morning stiffness OSTEOARTHRITIS degenerative joint disease progressive erosion of articular cartilage multifactorial disease that has genetic and environmental components

9 ANKYLOSING SPONDYLOARTHRITIS destruction of articular cartilage and bony ankylosis Men>women Major risk is genetics GOUTY ARTHRITIS transient attacks of acute arthritis crystallization of urates and deposit in joints REITER SYNDROME reactive arthritis arthritis, nongonococcal urethritis or cervicitis, and conjunctivitis Caused by autoimmune reaction initiated by prior infection of the gastrointestinal tract and the genitourinary system THE SKELETAL MUSCLE

10 DENERVATION ATROPHY Neurogenic atrophy of muscle is caused by disorders that affect motor neurons Spinal Muscular Atrophy Source: midlandstech.edu SPINAL MUSCULAR ATROPHY (INFANTILE MOTOR NEURON DISEASE) progressive neurologic illnesses destruction of the anterior horn cells in the spinal cord and cranial nerve motor neurons autosomal recessive motor neuron diseases childhood or adolescence mutations on chromosome 5 that is required for motor neuron survival Morphology atrophic fibers, often only a few micrometers in diameter panfascicular atrophy Robbins, Stanley L, Vinay Kumar, and Ramzi S Cotran. Robbins And Cotran Pathologic Basis Of Disease. 1st ed. Philadelphia, PA: Saunders/Elsevier, Print.

11 MUSCULAR DYSTROPHIES inherited disorders of muscle childhood progressive weakness and muscle wasting muscle fibers undergo degeneration and are replaced by fibrofatty tissue and collagen X-Linked Muscular Dystrophy X-LINKED MUSCULAR DYSTROPHY Duchenne muscular dystrophy (DMD) most severe and common form incidence of about 1 per 3500 live male births clinically manifest by the age of 5 years wheelchair dependence by years gene that is located in the Xp21 region that encodes a 427-kD protein named dystrophin two thirds of the cases are familial DYSTROPHIN cytoplasmic protein located adjacent to the sarcolemmal membrane in myocytes connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane muscle biopsy show little or no dystrophin by both staining and western blot analysis Robbins, Stanley L, Vinay Kumar, and Ramzi S Cotran. Robbins And Cotran Pathologic Basis Of Disease. 1st ed. Philadelphia, PA: Saunders/Elsevier, Print.

12 DISEASES OF THE NEUROMUSCULAR JUNCTION Myasthenia Gravis immune-mediated loss of acetylcholine receptor prevalence of about 30 in 100,000 persons commonly seen in women equally in both sexes in older patients decrease in the number of muscle acetylcholine receptors (AChRs), due to circulating antibodies to the AChR CLINICAL COURSE weakness begins with the extraocular muscles; drooping eyelids (ptosis) initial symptoms can also be generalized weakness respiratory compromise was a major cause of mortality in the past treatment include anticholinesterase drugs, prednisone, plasmapheresis, and thymectomy THE END TUMORS OF SKELETAL MUSCLE Rhabdomyosarcoma most common soft-tissue sarcoma childhood and adolescence any anatomic location