Dr. Stanescu Office: Gittings Room 108 email: [email protected] Office phone: 621-2795 Office Hours in Gittings 108 Tue 10-11am and Thurs 1-2pm or by appointmentLevels of organization • Chemical/ molecular • Cellular • Tissue • Organ • Organ system • Organism Organ systems we will cover this semester: skeletal, muscular, nervous Already coveredHow to study: • Focus on the information presented in lecture • Read the textbook to clarify difficult concepts and use the figures to study anatomy – Highlight structures on figures mentioned in class and ignore terms that are not discussed • Test your knowledge – can you remember what you just read?Objectives: 1. List and describe the functions of the skeletal system. 2. Differentiate between the two divisions of the skeletal system and give examples. 3. Describe the classification of bone based on shape, giving examples for each type. 4. Describe the anatomy of a long bone. 5. List and describe the functions of the 4 cell types found in bone. 6. Discuss modeling and remodeling of bone.Skeletal system components • Skeletal system contains bones, cartilage, ligaments, and other connective tissues that attach bones to each other • Each bone is an organ – contains bone connective tissue, blood vessels, nerves, lymph vessels, cartilage, connective tissue coveringsSkeletal System Functions 1) Support 2) Protection 3) Mineral storage 4) Triglyceride storage 5) Red and white blood cell formation (hemopoiesis) 6) Leverage (assistance in movement)Divisions of the skeletal system Axial Division Appendicular DivisionClassification of bones Sutural boneAnatomy of a Long Bone Diaphysis Epiphysis Epiphysis Metaphysis Metaphysis Medullary Cavity Periosteum Endosteum Articular Cartilage Articular Cartilage Spongy Bone (Trabecular) Compact Bone Endosteum and periosteum are important for bone growth and remodelingPeriosteum Periosteum • Connective tissue membrane covering external surface of bone • Continuous with tendons, connective tissue of joints • Attached to bone matrix via perforating fibers 2 Layers: 1) Outer fibrous 2) Inner osteogenicEndosteum • Lining inner surfaces of bone including marrow cavity, trabecullae of spongy bone, canals of compact bone • Contains osteogenic cells - important for bone growth and remodeling EndosteumComposition of bone • “Osteo” = bone • Osteology – the study of bone tissue Connective tissue Extracellular Matrix Cells Fibers Ground Substance Osteogenic cells Osteoblasts Osteocytes Osteoclasts Collagen Fibers (organic) Contains organic and inorganic components (GAG, water, minerals)Important in bone remodeling Connective tissue Cells Osteogenic cells Osteoblasts Osteocytes OsteoclastsOsteogenic (osteoprogenitor) cells • Stem cells that are formed from mesenchyme (embryonic connective tissue) Osteogenic cells Daughter osteogenic cells Osteoblasts Mitosis DifferentiationOsteoblasts • Cells that build bone  bone formation • Synthesize organic components of matrix • Initiate calcification – take calcium from blood and deposit it within matrix by exocytosis Immature cellsOsteocytes • Mature cells involved in maintenance of bone Osteoporosis, 3rd ed, Marcus, Feldman, Nelson, Rosen. Bone form and function. 2008 Osteocyte with its dendritic processesOsteoclasts • Break down bone  bone resorption • Release proteolytic enzymes and acids to degrade collagen and release minerals to blood • Derived from myloid stem cells (not osteogenic cells)Bone modeling/remodeling • Bone modeling (construction) is the process by which bone is formed by osteoblasts without prior bone resorption – Happens during growth – Produces change in bone size and shape • Bone remodeling (reconstruction) occurs when bone is first resorbed by osteoclasts and then formed in the same location by osteoblasts – Happens throughout lifeGoal of modeling / remodeling Achieve strength for loading and lightness for mobility. How? 1) Strategically deposit bone where it is needed 2) Remove bone from where it is not needed to avoid bulkDuring growth  To achieve the skeleton’s peak strength Goal of modeling / remodeling During adulthood  To maintain bone strength by removing damaged boneBone develops fatigue damage Just like roads and buildings, bone develops fatigue damage during repeated loading Bone is able to: 1. Detect location and magnitude of damage 2. Remove damage 3. Replace it with new bone 4. Restore bone’s material composition, micro and macroarchitecture1. ACTIVATION: preosteoclasts are stimulated and differentiate under the influence of cytokines and growth factors into mature active osteoclasts 2. RESORPTION: osteoclasts digest mineral matrix (old bone) Bone Remodeling 3. REVERSAL: end of resorption; recruitment of osteoblasts 4. FORMATION: osteoblasts synthesize new bone matrix 5. QUIESCENCE: osteoblasts become resting bone lining cells on the newly formed bone surface