NURS 8022 Patho - Exam #5 Study Guide.

Musculoskeletal Define differences between bone cells  Osteogenic cell: stem cell  Osteoblasts: bone forming cells, “bone-builders” o Derived from mesenchymal cells o Produce osteocalcin when stimulated by vitamin D o Form new bone – synthesize osteoid – brings on the formation of new bone – nonmineralized bone matrix o Follow Wolfe’s law: bone is shaped according to its function o Become osteocytes that are imbedded in bone  Osteoclasts: bone resorbing, “bone-crushers” o Large, multinucleated cells o Attached to integrins by podosomes (helps bind to bone) o Cause resorption of bone by secretion of HCl acid and a protease enzyme which help dissolve bone minerals and collagenase o Are “resting” when not resorbing  Resting osteoclast = once reabsorption is complete then disappears by degeneration reverting back to its parent cell or leaving the site  Osteocytes: bone maintaining o Develop dendritic processes that extend to either the bone surface or the bone’s vascular space o Help maintain bone by signaling osteoblasts and osteoclasts to form and resorb bone o Coordinate osteoblast and osteoclast functions o Respond to parathyroid hormone Understand basics of bone remodeling and bone repair  Bone formation: o First step: develop bone matrix; Final step: calcification or mineralization  Mineralization phases: formation of the initial mineral deposit (initiation) - proliferation of accretion of additional mineral crystals on the initial mineral deposits (growth)  End-product of mineralization is hydroxyapatite: majority of the mineral content in the body made of small crystals containing calcium and phosphate  Modeling: when a bone is formed at one site and broken down in a different site, its shape and position is changed  Remodeling: removal and replacement of bone at the same site o Regulation  Genes, environment, diet, physical activity  Hormones: calcium regulating (PTH, calcitriol [active vit.D], calcitonin); sex hormones (estrogen, testosterone); other systemic hormones (GH, insulin-like GF, thyroid hormone, cortisol)  Local regulation via cytokines, GF’s  RANK/RANKL/OPG system o RANK: receptor on osteoclast precursor and mature osteoclast cells o RANKL: receptor ligand; secreted by osteoblasts o OPG: decoy receptor produced by osteoblasts and stroll cells that binds to and sequesters RANKL – inhibits osteoclast differentiation, fusion, and activation NURS8022 Patho - Exam #5 Study Guide. o Bone-remodeling units o Repair of microscopic injuries and maintenance of bone integrity o Phases:  Activation of the remodeling cycle  Resorption  Formation of new bone (secondary bone)  Takes 3-4 months  Repair: bone heals itself o Hematoma formation – clot forms o Procallus formation – produces granulation tissue o Callus formation – forms membranous or woven bone o Callus replacement – replaces the callus with lamellar bone or trabecular bone o Remodeling – periosteal and endosteal surfaces are remodeled to the size and shape of the bone before the injury Understand difference between compact and spongy bone  Bone matrix: 35% organic; 65% inorganic; 5-8% water o Organic: collagen fibers, proteoglycans, glycoproteins, osteocalcin, osteonectin, osteopontin, cytokine, growth factors; inorganic: calcium and phosphate minerals  Collagen: essential for strength, form fibrils that twist, synthesized by osteoblasts  Proteoglycans: strengthen bone by forming compression-resistant networks between collagen, help calcium deposit in bone - act as a pump – permit fluid to be pressed out to ensure that fluid film is always present on the surface of cartilage even after hours of weight bearing  Glycoproteins: carb-protein complexes of bone, play a role in calcification  Osteocalcin: most abundant non-collagenous protein, produced by osteoblasts, promotes mineralization and formation of bone, attracts osteoclasts, signals vitamin D, inhibited by PTH; marker of bone turnover, can be measured in urine or serum  Osteonectin: secreted by platelets & osteoblasts, role in regulating calcium, organizing matrix  Osteopontin: cell binding protein  Cytokine and growth factors: aid in bone cell differentiation, activation, growth, and turnover  Compact bone: cortical bone – outer bone, rigid o 85% of skeleton o Solid and extremely strong o Haversian system: basic structural unit in compact bone  Spongy bone: cancellous bone – inner bone, porous o 15% of skeleton o Filled with red bone marrow o Trabeculae: plates or bars instead of Haversian system  Periosteum: double-layered connective tissue that covers all bones o Outer layer: contains blood vessels and nerves, some of which penetrate to inner bone structures through channels called Volkmann canals o Inner layer: anchored to the bone by collagenous fibers (Sharpey fibers) that penetrate the bone and help hold or attach tendons and ligaments to the periosteum of bones  Characteristics of bone  Long bones  Diaphysis: medullary cavity contains fat = yellow marrow  Metaphysis: broad neck  Epiphysis: epiphyseal plate – epiphysis is separated from metaphysis by cartilaginous growth plate; after puberty, epiphyseal plate calcifies and the epiphysis and metaphysis merge o Medullary cavity helps with blood formation = red marrow  Endosteum: lines medullary cavities o Flat bones  Two plates of compact bone, parallel to each other – spongy bone is between the compact bone o Short bones (cuboidal bones)  Consist of spongy bone covered by a thin layer of compact bone o Irregular bones  Thin part: two plates of compact bone with spongy bone between the plates  Thick part: consists of spongy bone surrounded by a layer of compact bone Describe different joint classifications  Joints: the sites where two or more bones meet o Promote stability and mobility of the skeleton – help move bones and muscles o Classifications: based on movement  Synarthrosis: immovable  Amphiarthrosis: slightly movable  Diarthrosis: freely movable o Classifications: based on structure  Fibrous: directly united to bone by dense fibrous connective tissue  Usually are synarthroses (immovable) but most allow some movement o Degree of movement depends on distance between the bones and the flexibility of the fibrous connective tissue o Ex: sutures  Cartilaginous: connected by fibrocartilage or hyaline cartilage  Symphysis: bones are united by a pad or disk of fibrocartilage o Ex: symphysis pubis and intervertebral disks  Synchondrosis: bones are united by hyaline cartilage (costal cartilage) o Ex: joints between ribs and the sternum  Synovial: most movable, most complex, diarthrosis  Fibrous joint capsule: articular capsule  Synovial membrane: lines the inner surface of the joint capsule  Joint cavity (synovial cavity): space is formed by the capsule  Synovial fluid: fills the joint cavity and lubricates the joint surface  Articular cartilage: hyaline cartilage - covers and pads the articulating bony surfaces o Reduces friction in the joint and distributes forces of weight bearing o Composed of chondrocytes (cartilage cells) and an intercellular matrix (collagen, polysaccharides and mostly water)