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1H06 Anatomy & Physiology: MSK Bones, Joints, Movements

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McMaster University
Health Sciences
Alexander Ball

MSK Bones, Joints, Movements  Bone tissue continuously growing, remodeling, and repairing  Provides homeostasis with support and protection, producing blood cells, storing minerals and triglycerides  Bone made of osseous tissue, cartilage, dense connective tissues, epithelium, adipose tissue, and nervous sittue Functions of Bone and Skeletal System 1. Support a. Structural framework – attachment for tendons of skeletal muscles 2. Protection a. Protects important internal organs from injury 3. Assistance in movement a. Most skeletal muscles attach to bones; when contract, they pull on bones to produce movement 4. Mineral homeostasis a. Bone stores 99% of body’s calcium b. Releases minerals into blood to maintain mineral balances and distribute minerals to other body parts 5. Blood cell production a. Red bone marrow – produces red blood cells, white blood cells, and platelets called hemopoiesis b. Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and microphages 6. Triglyceride storage a. Yellow bone marrow consists mainly of adipose cells, which store triglycerides and used as energy reserve Structure of Bone Long bone consists of: 1. Diaphysis – shaft or body 2. Epiphyses – proximal and distal ends 3. Metaphyses – regions between diaphysis and epiphyses a. Each metaphysis contains epiphyseal plate (layer of hyaline cartilage allowing diaphysis of bone to grow in length) 4. Articular cartilage – thin layer of hyaline cartilage covering part of epiphysis where bone forms articulation with another bone a. Articular cartilage reduces friction and absorbs shock at freely movable joints 5. Periosteum – tough connective tissue sheath and blood supply that surrounds bone surface when not covered by articular cartilage a. Outer fibrous layer of dense irregular connective tissue b. Inner osteogenic layer contains cells – some enable bone to grow in thickness but not length c. Periosteum also protects bone, assists in fracture repair, nourish bone tissue 6. Medullary cavity – hollow space within diaphysis that contains fatty yellow bone marrow and blood vessels a. Cavity minimizes weight of bone by reducing dense bony material where it is least needed Histology of Bone Tissue  Contains extracellular matrix of 15% water, 30% collagen fibers, 55% crystallized mineral salts  Different salts crystallize (calcification), initiated by osteoblasts (bone- building cells)  Combination of crystalized salts and collagen fibers gives bone its characteristics  Bone’s hardness depends on crystallized inorganic mineral salts, flexibility depends on collage fibers Types of cells in bone: 1. Osteogenic a. Unspecialized stem cells derived from mesenchyme b. Only cells to undergo cell division, form osteoblasts c. Found along inner periosteum, in endosteum, and canals within bone that contain blood vessels 2. Osteoblasts a. Bone-building cells that create and release collagen fibers and other organic components needed to build extracellular matrix of bone tissue, and initiate calcification b. Surround themselves with ECM, become trapped in their secretions and become osteocytes 3. Osteocytes a. Mature bone cells, main cells in bone tissue and maintain metabolism (exchange of nutrients and wastes with blood) b. Do not undergo cell division 4. Osteoclasts a. Huge, derived from fusion of up to 50 monocytes and concentrated in endosteum b. Ruffled border – cells there relase enzymes and acids that digest protein and minerals of ECM (resorption)  osteoBlasts Build bone, osteoClasts Carve out bone Compact Bone Tissue  contains few spaces, strongest form of bone tissue  under periosteum of all bones, makes up bulk of diaphyses of long bones  provides protection and support and resists stresses produced by weight and movement Spongy Bone Tissue  located in interior of bone, protected by covering of compact bone  consists of lamellae arranged in irregular pattern of thin columns (trabeculae)  makes up most of interior bone tissue of short, flat ,sesamoid, and irregular bones Blood and Nerve Supply of Bone  Bone richly supplied with blood  Blood vessels pass into bones from periosteum  Periosteal ateries enter diaphysis through perforating canals and supply periosteum and outer compact bone  Large nutrient artery passes through hole in compact bone (nutrient foramen)  Nutrient artery divides into proximal and distal brances that course toward each end of bone, and supply both inner part of compact bone tissue of diaphysis and spongy bone tissue and red bone marrow  Metaphyseal arteries supply red bone marrow and bone tissue of metaphyses  Epiphyseal arteries supply red bone marrow and tissue of epiphyses Bone Formation  Two types: intramembranous ossification (bone forms directly within mesenchyme, arranged in sheetlike layers that resemble membranes)  Endochondral ossification – bone forms within hyaline cartilage that develops from mesenchyme Intramembranous ossification 1. Development of ossification center a. Mesenchyma
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