Musculoskeletal System
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Bio217 Unit X Bio217: Pathophysiology Notes Skeletal System Professor Linda Falkow • Forms the body Unit X: Musculoskeletal System & • Supports tissues Integumentary System • Permits movement – by providing attachment points Chapter 36:Musculoskeletal System for muscles • Hemopoiesis (blood cell formation) Chapter 37:Alterations of Musculoskeletal Function • Mineral storage Chapter 39: Structure, Function & Disorders of the Integumentary System Elements of Bone Tissue Bone Cells • Rigid connective tissue Enable bone to grow, repair, synthesize new bone tissue and • Constituents resorb old tissue – Cells Osteoblast – Fibers – Bone forming cell – Ground substance Osteoclast – – Calcium Reabsorptive bone cell Osteocyte – Transformed osteoblast, maintains matrix Bone Matrix Bone Tissue extracellular components • Compact (cortical) bone • Collagen fibers – tensile strength – 85% of the skeleton – Haversian system (osteon) • Proteoglycans - strengthen bone, transport Ca++ • Haversian (central) canal, lamellae, lacunae, osteocyte, and canaliculi • Glycoproteins – regulate collagen interactions fibril formation • Spongy (cancellous) bone • Bone mineralization – crystals of HAP – Lack haversian systems (hydroxyapatite) (Ca & PO4) – Trabeculae • Periosteum 1 Bio217 Unit X Bone Tissue Bone Structure of • 206 bones compact bone • Axial skeleton – 80 bones & • Skull, vertebral column, thorax • Appendicular skeleton cancellous bone – 126 bones • Upper and lower extremities, pectoral and pelvic girdle Bones Long Bone • Long bones – Upper and lower extremities • Flat bones Longitudinal – Ribs and scapulae section of • Short bones (cuboidal bones) long bone – Wrist and ankles • Irregular bones – Vertebrae, mandibles, facial bones Bone Remodeling and Repair Joints Bone remodeling • Joint classifications based on movement – Maintains internal structure – Synarthrosis – Repair microscopic injuries • Immovable Bone Repair – Amphiarthrosis – Fractures and gross injuries • Slightly movable – Inflammation/hematoma formation – Procallus formation – Diarthrosis – Callus formation • Freely movable – Callus replacement – Remodeling 2 Bio217 Unit X Joints Joints • Joint classifications based on structure – Fibrous A. Synchondrosis E. Suture • Joins bone to bone • Suture, syndesmosis, gomphosis B. Symphysis F. Ball & socket – Cartilaginous • Symphysis and synchondrosis – Synovial C. Symphysis G. Hinge • Uniaxial, biaxial, or multiaxial • Joint capsule, synovial membrane, joint cavity, D. Syndesmosis H. Gliding synovial fluid, articular cartilage Joints Synovial Joint Movements Knee Joint (synovial) Body Movements by Synovial Joints Joints Skeletal Muscles • Millions of individual muscle fibers (= muscle cells) contract and relax to facilitate movement • More than 600 in body • 2 to 60 cm long 3 Bio217 Unit X Skeletal Muscles Skeletal Muscles Whole muscle – Fascia (3 part CT framework) – Epimysium Entire belly of muscle – Perimysium Fascicles (bundles of muscle fibers) – Endomysium Individual muscle fiber Muscle Muscle Fibers • Sarcotubular system • Skeletal muscle – Transverse tubules – Sarcoplasmic reticulum (SR) – Voluntary – Striated • Sarcomere (myofibrils) – Motor units – Muscle proteins • Actin • Myosin • Troponin-tropomyosin complex • Nonprotein components: – Creatine and creatinine – Phosphate, chloride, calcium, magnesium, sodium, potassium Myofibrils Myofibrils 4 Bio217 Unit X Muscle Contraction Muscle Metabolism • Excitation • Requires constant supply of ATP and – Muscle fiber action potential phosphocreatine (CP creatine phosphate) • Coupling • Contraction • Strenuous activity requires oxygen – Cross-bridge theory • Relaxation • Type I fibers can resist fatigue longer than type II fibers • 3. Joints are classified functionally & structurally. Which is a correct Concept Check functional/structural relationship? • A. Amphiarthrosis/fibrous C. Synarthrosis/ synchrondrosis • 1. The skeletal system: • B. Diarthrosis/ synovial D. Diarthrosis/ fibrous – A. Supports tissues E. Synarthrosis/ cartilaginous – B. Binds organs together • 4. Which is not included in a motor unit? – C. Protects CNS structures – A. Muscle fibers – D. Involved in blood cell production – B. Motor nerve axons – C. Anterior horn cell – E. Lines body cavities – D. Upper motor neuron • 2. A function of the epiphyseal plate that is not a • 5. Which are correctly matched? function of articular cartilage: – A. Sarcomere – unit of contraction – B. Sarcolemma – membrane covering the muscle cell – A. Enable articulation of bones – C. Sarcoplasmic reticulum – Ca storage and transport – B. Enable bones to increase in length D. All of the above are correct – C. Repair damaged bone – D. Provide sensory nerves to bone Musculoskeletal Injuries • Fractures • Alterations of Musculoskeletal Function = break in a bone – Classifications • Complete or incomplete (broken completely through or not) • Chapter 37 –Closed or open (compound) (skin intact or skin is broken) • Comminuted - fragmented • Linear – break is parallel to long axis of bone • Oblique – break at an oblique angle • Spiral – encircles bone • Transverse – at right angles to long axis 5 Bio217 Unit X Fracture Classifications Fractures • Greenstick – incomplete break • Torus - buckling of bone • Bowing – bending of bone • Pathologic – due to disease (osteoporosis) • Stress – microfracture often due to repeated stress, common in athletes Bone Fractures Callus Formation Pathophysiology A. Hematoma Bleeding at ends of bone B. Fibrous – Hematoma formation network Bone tissue destruction inflammatory response – Procallus formation C. Ca deposition – Callus formation – Callus reabsorption – Remodeling D. Callus fomation E. Remodeling Callus Formation Bone Fractures Dislocation Excessive callus – Temporary displacement of two bones formation – Loss of contact between articular cartilage Subluxation – Contact between articular surfaces is only partially lost Both caused by trauma 6 Bio217 Unit X Support Structure Injuries Tendinopathy and Bursitis • Strain • Tendinitis – Tear or injury to a tendon – Inflammation of a tendon • Sprain • Bursitis – Tear or injury to a ligament – Inflammation of a bursa • Avulsion – Complete separation of a tendon or • Epicondylitis ligament from its bony attachment site – Inflammation of a tendon where it attaches to bone • Tennis elbow (lateral epicondylitis) • Golfer’s elbow (medial epicondylitis) Tendinopathy and Bursitis Rhabdomyolysis • Rhabdomyolysis (myoglobinuria) is a life- threatening complication of severe muscle trauma with muscle cell loss – Excess myoglobin in urine due to muscle damage • Pathophysiology – Wt. of limp extremity ischemia edema necrosis (cell loss) Osteoporosis Osteoporosis • Metabolic bone disorder decreased bone mass • Potential causes (bone resorption >> bone deposition) – Decreased levels of estrogens and • Porous bone testosterone • Poorly mineralized bone – Decreased activity level • Bone density – Inadequate levels of vitamins D, C, or Mg++ – Normal bone : 833 mg/cm2 (diet or absorption problems) – Osteopenic bone : 833 to 648 mg/cm2 – Osteoporosis: <648 mg/cm2 7 Bio217 Unit X Osteoporosis Osteoporosis Vertebral body – normal on left; compression fractures of osteoporosis on right Osteoporosis Osteoporosis Iatrogenic osteoporosis – Patients on heparin ( bone resorption) Regional osteoporosis – Disuse of body region, or weightlessness uniform dist. of bone loss Postmenopausal osteoporosis – Decreased level of estrogens, or hyperparathryoidism Glucocorticoid-induced osteoporosis (cortisone incr. bone resorption, decr. formation) Age-related bone loss –begins in 4th decade Osteoporosis Osteoporosis 8 Bio217 Unit X Osteomalacia Paget Disease • Abnormal remodeling - irregular resorption and Metabolic disorder inadequate deposition of bone mineralization (aka adult rickets) – (aka osteitis deformans) Deficiency of vitamin D lowers the absorption of Ca from the intestines • Disorganized, thickened, but soft bones Bone formation progresses to osteoid • Most often affects the axial skeleton formation but calcification does not – Skull thickens compresses brain tissue occur soft bones – cranial nerves impacted – Pain, bone fractures, vertebral collapse, bone – hearinig loss malformation • Idiopathic, viral ? Osteomyelitis Osteomyelitis Pathophysiology: Infectious bone disorder – Bone infection inflammatory response Caused by a staphylococcal infection (vascular engorgement, edema incr. WBCs, abcess formation – Exudate can seal canaliculi , extend into Most common cause is open wound metaphysis and marrow (exogenous); also can be from blood- borne (endogenous) infection Manifestations – Acute and chronic inflammation, fever, pain, necrotic bone Treatment – Antibiotics, débridement, surgery, hyperbaric oxygen therapy Osteomyelitis Osteomyelitis Osteomyelitis showing sequestration and involucrum 9 Bio217 Unit X Osteoarthritis Osteoarthritis (OA) • aka Inflammatory Joint Disease Most common form of arthritis erosion of articular cartilage • Characterized by inflammatory bone spurs (osteophytes) damage or destruction in the synovial membrane or articular Age related cartilage and by systemic signs of inflammation Affects mostly hips and knees, can affect any joint – Fever, leukocytosis, malaise, anorexia, and hyperfibrinogenemia Primary disease is idiopathic (metabolic factors, genetics, chemical & mechanical factors) Osteoarthritis Osteoarthritis OA characterized by local areas of damage and Degeneration loss of articular cartilage, new bone formation of joint margins,