Bio217 Fall 2012 Unit X Bio217: Pathophysiology Notes Skeletal System Professor Linda Falkow • Forms the body Unit X: Musculoskeletal System & • Supports tissues Integumentary System • Permits movement Chapter 36: Musculoskeletal System – by providing attachment points 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 – Fibers . Osteoblast – Ground substance Bone forming cell . 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 Fall 2012 Unit X Bone Tissue Bone Structure of • 206 bones compact bone • Axial skeleton – 80 bones & • Skull, vertebral column, thorax cancellous bone • Appendicular skeleton – 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 Fall 2012 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 Fall 2012 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 Fall 2012 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 Fall 2012 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 C. Ca deposition – Procallus formation – Callus formation – Callus reabsorption D. Callus fomation – Remodeling 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 Fall 2012 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 Fall 2012 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 Fall 2012 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 Fall 2012 Unit X Osteoarthritis Osteoarthritis (OA) • aka Inflammatory Joint Disease Most common form of arthritis erosion of articular cartilage • Characterized by inflammatory damage or bone spurs (osteophytes) destruction in the synovial membrane or articular cartilage and by systemic signs Age related of inflammation – Fever, leukocytosis, malaise, anorexia, and Affects mostly hips and knees, can affect any joint hyperfibrinogenemia Primary disease is idiopathic (metabolic factors, genetics, chemical & mechanical factors) Osteoarthritis Osteoarthritis OA characterized by