Chapter 41 Structure and Function of the Musculoskeletal

Chapter 41 Structure and Function of the Musculoskeletal System Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 1

Skeletal System Forms the body Supports tissues Permits movement by providing points of attachment for muscles Site of blood cell formation Mineral storage Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 2

Bone Rigid yet flexible connective tissue Constituents Cells Ø Fibers Ø Ground substance Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 3

Bone Tissue Osteoblasts Derived from mesenchymal cells Ø Produce type I collagen Ø Respond to parathyroid hormone Ø Produce osteocalcin Ø Synthesize osteoid • Nonmineralized bone matrix Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 4

Bone Tissue Osteocyte Ø Transformed osteoblast surrounded in osteoid as it hardens from deposited minerals Osteoclast The major reabsorptive cell of the bone Ø Large, multinucleated cells Ø Contains lysosomes filled with hydrolytic enzymes Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 5

Bone Matrix 35% organic and 65% inorganic Collagen fibers Calcium and phosphate minerals Proteoglycans Glycoproteins Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 6

Bone Tissue Compact (cortical) bone 85% of the skeleton Ø Haversian system • Haversian canal, lamellae, lucunae, osteocyte, and Ø canaliculi Spongy (cancellous) bone Lack haversian systems Ø Trabeculae Ø Periosteum Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 7

Compact Bone Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 8

Bone 206 bones Axial skeleton Ø 80 bones • Skull, vertebral column, thorax Appendicular skeleton Ø 126 bones • Upper and lower extremities, the shoulder girdle, the pelvic girdle Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 9

Skeleton Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 10

Bones Long bones Diaphysis Ø Metaphysis Ø Epiphysis • Epiphyseal plate Ø In a child epiphysis is separated from metaphysis by a cartilaginous growth plate. After puberty epiphyseal plate calcifies and epiphysis and metaphysis merge • Epiphyseal line Ø Medullary cavity Ø Endosteum Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 11

Long Bone Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 12

Bones Flat bones Short bones (cuboidal bones) Irregular bones Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 13

Bone Remodeling Bone-remodeling units Repairs microscopic injuries and maintains bone integrity Phases Activation of the remodeling cycle Ø Reabsorption Ø Formation of new bone Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 14

Bone Remodeling Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 15

Bone Wound Healing Hematoma formation Procallus formation Callus replacement Remodeling Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 16

Joints Site where two or more bones meet Promote stability and mobility of the skeleton Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 17

Joints Joint classifications based on movement Synarthrosis • Immovable Ø Amphiarthrosis • Slightly movable Ø Diarthrosis • Freely movable Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 18

Joints Joint classifications based on structure Fibrous Usually synarthroses (immovable) Ø However, many allow some movement • Degree of movement depends on the distance between Ø the bones and the flexibility of the fibrous connective tissue Ø Sutures, syndesmoses, and gomphoses Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 19

Joints Joint classifications based on structure Cartilaginous • Symphysis Bones are united by a pad or disk of fibrocartilage Example: symphysis pubis, intervetebral disks • Synchondrosis Bones are united by hyaline cartilage Example: joints between the ribs and the sternum Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 20

Joints Classifications based on structure Synovial (most movable, most complex) contain: A fibrous joint capsule (articular capsule) Ø Synovial membrane that lines inner surface of joint capsule Ø Joint cavity (synovial cavity), a space formed by the capsule Ø Synovial fluid, which fills the joint cavity and lubricates joint surface Ø Articular cartilage, which covers and pads the articulating bony surfaces Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 21

Joints Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 22

Joints Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 23

Joints Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 24

Joints Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 25

Joints Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 26

Skeletal Muscles Millions of individual muscle fibers that contract and relax to facilitate movement 75% water, 20% protein, 5% organic and inorganic compounds 350 named muscles (most are paired) 2 to 60 cm long Fusiform muscles Pennate muscles Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 27

Skeletal Muscles Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 28

Skeletal Muscles Whole muscle Fascia Ø Epimysium Ø Tendon Ø Perimysium Ø Fascicles Ø Endomysium Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 29

Muscle Skeletal muscle Voluntary • Controlled directly by the central nervous system Ø Striated • The striated, or striped, pattern of skeletal muscle • Result from organization of muscle fibers into the contractile Ø units called sarcomeres Ø Extrafusal • Distinguishes skeletal muscle fibers from other contractile fibers Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 30

Muscle Motor unit (anterior horn cell, its axon, and its muscle fiber) Anterior horn cell of the spinal cord Ø Axons of motor nerves branch out to innervate a specific group of muscle fibers; lower motor neurons Ø Functional unit of the neuromuscular system Ø Innervation ratio Sensory receptors Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 31

Motor Units Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 32

Muscle Innervation ratio Motor units per muscle Ø The greater the innervation ratio of a particular organ, the greater its endurance Ø Higher innervation ratios prevent fatigue Ø Lower innervation ratios allow for precision of movement Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 33

Muscle Sensory receptors (send signals to the central nervous system) Spindles • Mechanoreceptors that lie parallel to muscle fibers • Respond to muscle stretching Ø Golgi tendon organs: dendrites that terminate and branch to tendons near the neuromuscular junction Ø Spindles, Golgi tendon organs, and free nerve endings report changes in muscle length, tension, velocity Ø System of afferent signals responsible for muscle stretch response and maintaining muscle tone Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 34

Muscle Fibers Myofibrils Myoblasts White muscle (type II fibers) Red muscle (type I fibers) Muscle membrane Ø Sarcolemma and basement membrane Sarcoplasm Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 35

Muscle Fibers Sarcotubular system Transverse tubules Ø Sarcoplasmic reticulum Ø Sarcomere Actin Ø Myosin Ø Troponin-tropomyosin complex Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 36

Myofibrils Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 37

Myofibrils Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 38

Muscle Fibers Creatine and creatine kinase Phosphate, chloride, calcium, magnesium, sodium, potassium Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 39

Muscle Contraction Activation Ø Coupling Contraction Ø Muscle fiber action potential Cross-bridge theory Relaxation Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 40

Muscle Contractions and Movement Types of contractions Isometric Ø Isotonic • Eccentric • Concentric Ø Muscle movement Agonist Ø Antagonist Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 41

Test of Bone Function Gait analysis Serum calcium and phosphorus X-rays Angiography Bone scanning Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 42

Test of Joint Function Arthrography Arthroscopy MRI Synovial fluid analysis Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 43

Test of Muscular Function Serum creatine kinase Myoglobin EMG Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 44

Aging and the Musculoskeletal System Bones Bone loss Ø Stiff, brittle, decreased strength Ø Bone remodel time is lengthened Ø Joints Cartilage becomes more rigid, fragile, stiff Ø Decreased range of motion Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 45

Aging and the Musculoskeletal System Muscles Sarcopenia Ø Decrease in muscle strength and bulk Ø Reduced oxygen intake, basal metabolic rate, and lean body mass Ø Mosby items and derived items © 2010, 2006 by Mosby, Inc. , an affiliate of Elsevier Inc. 46