UNBC Musculoskeletal System PDF

Structure and Function of the MusculoSkeletal System Nursing 302 Structure and Function of Bones Gives form to the body Supports tissues Permits movement by providing points of attachment for muscles Protects many vital organs Serves as a site for blood cell formation Play...

Structure and Function of the MusculoSkeletal System Nursing 302 Structure and Function of Bones Gives form to the body Supports tissues Permits movement by providing points of attachment for muscles Protects many vital organs Serves as a site for blood cell formation Plays a role in mineral and hormone homeostasis Elements of Bone Tissue Rigid connective tissue Constituents Cells Fibres Ground substance Crystallized minerals Elements of Bone Tissue (Cont.) Bone cells enable bone to grow, repair, change shape, synthesize new bone tissue, and resorb old tissue Bone matrix Calcification Bone Cells Osteoblasts Derived from mesenchymal stem cells Primary bone-producing cells Respond to parathyroid hormone Produce osteocalcin Synthesize osteoid Nonmineralized bone matrix Express the cytokine receptor activator nuclear factor kappa-B ligand (RANKL) Necessary for forming osteoclasts Bone Tissue Osteocytes Transformed osteoblasts that are surrounded in osteoid as it hardens from deposited minerals Synthesize matrix molecules Key regulators of both bone formation and resorption Osteoclasts Major reabsorptive cells of the bone Large, multinucleated cells Bone Cells A and C, from Damjanov, I., & Linder, J. (Eds.). (1996). Anderson’s pathology (10th ed.). St Louis, MO: Mosby; B, from Wikimedia Commons, courtesy Robert M. Hunt. A, Magnified view of compact bone. B, Longitudinal section of a long bone showing both cancellous and compact bone. C, Section of a flat bone OPG/RANKL/RANK System Osteoprotegerin (OPG) Glycoprotein that inhibits bone remodelling/resorption, inhibiting osteoclast formation Key in the interaction between osteoblasts and osteoclasts RANKL is an essential cytokine needed for the formation and activation of osteoclasts When RANKL binds to its receptor RANK on osteoclast precursor cells, it triggers their proliferation and increases bone resorption Bone Matrix Collagen fibres Make up bulk of bone matrix Proteoglycans Strengthen bone Play role in bone calcium deposition and calcification Bone Matrix (Cont.) Glycoproteins Control collagen interactions that lead to fibril formation Sialoprotein, osteocalcin, bone albumin, α-glycoprotein Bone minerals Two phases of mineralization Formation of the initial mineral deposit Proliferation or accretion of additional mineral crystals on the initial mineral deposits Calcium and phosphate Bone Tissue Compact (cortical) bone 85% of the skeleton Highly organized, solid, and extremely strong Haversian system Haversian canal, lamellae, lacunae, osteocyte, and canaliculi Spongy (cancellous) bone Lack haversian systems Trabeculae Periosteum From Patton, K.T., & Thibodeau, G.A. (2016). Anatomy & physiology (9th ed.). St Louis, MO: Mosby. Photo courtesy Dennis Strete. Characteristics of Bone 206 bones in human skeleton Axial skeleton 80 bones Skull Vertebral column Thorax Appendicular skeleton 126 bones Upper and lower extremities Shoulder girdle Pelvic girdle  Skeleton From Drake, R., Vogl, A.W., Mitchell, A.W.M., et al. (2015). Gray’s atlas of anatomy (2nd ed.). Philadelphia, PA: Churchill Livingstone. Bones Long bones Diaphysis Metaphysis Epiphysis Epiphyseal plate Medullary (marrow) cavity Endosteum Long Bone From Solomon, E. (2016). Introduction to human anatomy and physiology (4th ed.). St Louis, MO: Saunders. Bones Flat bones Ribs Scapulae Short bones (cuboidal bones) Wrists Ankles Irregular bones Vertebrae Mandibles Facial bones 1. Which is TRUE regarding the human skeleton? A. There are 280 bones in the skeleton. B. Axial skeleton consists of 126 bones. C. Skeleton contributes to 50% of total body weight. D. Axial skeleton consists of the skull, vertebral column, and thorax. Maintenance of Bone Integrity Remodelling Basic multicellular units Repair of microscopic bone injuries Existing bone is resorbed and new bone is laid down to replace it Three phases: Activation of the remodelling cycle Resorption Formation of new bone  Bone Remodelling Adapted from Nucleus Medical Art. D, from Damjanov, I., & Linder, J. (Eds.). Anderson’s pathology (10th ed.). St Louis, MO: Mosby. Bone Repair New bone is the final result Stages: Inflammation/hematoma formation Procallus formation Callus formation Callus replacement Remodelling Structure and Function of Joints Joint Also called articulation Site where two or more bones meet/attach Provides stability and mobility to the skeleton Joints Joint classifications based on movement Synarthrosis Immovable Amphiarthrosis Slightly movable Diarthrosis Freely movable Joints (Cont.) Joint classifications based on structure Fibrous Joins bone to bone Suture, syndesmosis, gomphosis Cartilaginous Symphysis and synchondrosis Synovial Uniaxial, biaxial, or multiaxial Joint capsule, synovial membrane, joint cavity, synovial fluid, articular cartilage Joints (Cont.) Joint (articular) capsule Fibrous connective tissue that covers the ends of bones where they meet in a joint Synovial membrane Smooth, delicate inner lining of joint capsule found in the nonarticular portion of the synovial joint and any ligaments or tendons that traverse this cavity Vascular subintima Thin cellular intima Joint (synovial) cavity Enclosed, fluid-filled space between articulating surfaces of two bones Enables two bones to move “against” one another Joints (Cont.) Synovial fluid Superfiltrated plasma from blood vessels Lubricates joint surfaces Nourishes the pad of the articular cartilage Covers the ends of the bones Articular cartilage Layer of hyaline cartilage that covers the end of each bone Reduces friction in the joint Distributes the forces of weight bearing Composed of chondrocytes and intracellular matrix. From Dorland. (2012). Dorland’s medical illustrated dictionary (32nd ed.). St Louis, MO: Saunders. Skeletal Muscles Millions of individual muscle fibres that contract and relax to facilitate movement 75% water, 20% protein, 5% organic and inorganic compounds More than 600 in body 2 to 60 cm long Fusiform muscles Elongated muscles shaped like straps Pennate muscles Broad, flat, and slightly fan-shaped Skeletal Muscles (Cont.) Epimysium Outermost layer Tendon Perimysium Fascicles Endomysium Smallest unit of muscle visible without a microscope Muscle Skeletal muscle Voluntary Striated Extrafusal Motor unit Functional unit of the neuromuscular system Composed of lower motor neurons Sensory receptors Spindles Golgi tendon organs Motor Units Muscle Fibres Each muscle fibre is a single muscle cell Myofibrils Fibre’s functional subunits Myoblasts Precursor cells Main cells responsible for muscle growth and regeneration Satellite cells Myoblasts in dormant state Muscle Fibres (Cont.) White muscle (type II fibres) Fast twitch Red muscle (type I fibres) Slow twitch Muscle membrane Sarcolemma and basement membrane Sarcoplasm Cytoplasm of the muscle cell Contains enzymes and proteins responsible for the cell’s energy production, protein synthesis, and oxygen storage Muscle Fibres (Cont.) Sarcotubular system Transverse tubules Sarcoplasmic reticulum Sarcotubules Sarcomere Muscle Fibres (Cont.) Myofibrils Functional units of muscle contraction Contains sarcomeres Speed with which sarcomeres lengthen and shorten during movement directly influences the strength and function of skeletal muscles Most abundant subcellular muscle component Composed of myofilaments Muscle Structure From Solomon, E. (2016). Introduction to human anatomy and physiology (4th ed.). St Louis, MO: Saunders. Muscle Nonprotein constituents of muscle Nitrogen, creatine, creatinine, phosphocreatine, purines, uric acid, and amino acids all serve in the complex process of muscle metabolism Energy is provided by glycogen Creatinine is formed in muscle from creatine Inorganic compounds, anions, and cations are important in the regulation of protein synthesis, muscle contraction, and enzyme systems, as well as in the stabilization of cell membranes Muscle Contraction Excitation Muscle fibre action potential Coupling Contraction Cross-bridge theory Relaxation Muscle Metabolism Requires constant supply of ATP and phosphocreatine During activity, the need for ATP increases 100-fold Stored glycogen and blood glucose are converted anaerobically to sustain brief activity without increasing the demand for oxygen Strenuous activity requires oxygen Type I fibres can resist fatigue longer than type II fibres Muscle Mechanics All or nothing response Repetitive discharge Allows the muscle to activate the number of motor units needed to generate the desired force Physiological tetanus Occurs when motor units are stimulated again and the muscle unit has not been able to relax between stimulation and the next contraction Muscle Contractions and Movement Types of muscle contractions Isometric Dynamic Eccentric Concentric Muscle movement Agonist Antagonist Dynamic and Isometric Contraction From Patton, K.T., & Thibodeau, G.A. (2016). Structure & function of the body (15th ed.). St Louis, MO: Mosby.. Tendons and Ligaments Tendons Ligaments Attach muscle to bone Attach bone to bone Transfer forces from muscle to Stabilize joints against excessive bone movement Act as a type of biological spring for muscles to allow additional stability during movement Aging and the Musculo-Skeletal System Bones Bone loss Less dense, less strong, more brittle Bone remodel time is lengthened Joints Cartilage becomes more rigid, fragile, susceptible to fraying Decreased range of motion Aging and the Musculo- Skeletal System (Cont.) Muscles Sarcopenia Decrease in muscle mass and strength Reduced oxygen intake, basal metabolic rate, and lean body mass