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The Skeletal System

The Skeletal System. Anatomy & Physiology Ms. Napolitano. Functions. Support Structural support Framework for attachment Storage Calcium reserve Energy reserves (lipids in yellow marrow) Blood Cell Production AKA hemopoiesis RBC and WBC produced in red marrow Protection

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The Skeletal System

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  1. The Skeletal System Anatomy & Physiology Ms. Napolitano

  2. Functions • Support • Structural support • Framework for attachment • Storage • Calcium reserve • Energy reserves (lipids in yellow marrow) • Blood Cell Production • AKA hemopoiesis • RBC and WBC produced in red marrow • Protection • Surrounds soft tissues and organs • Leverage for movement • Change magnitude and direction of forces generated by skeletal muscles

  3. Macroscopic Features of Bone Structure • Long Bones • Longer than they are wide • Ex: humerus, femur • Short Bones • Roughly equal length and width • Ex: carpals, tarsals • Flat Bones • Thin and broad • Ex: ribs • Irregular Bones • Complex shapes • Ex: pelvic girdle, vertebrae

  4. Features of Long Bones • Diaphysis • Central shaft • Bonemarrow • Yellow vs. red • Epiphysis • Enlarged ends • Covered with articular cartilage • Compactbone • Dense/solid • Found in diaphysis • Spongy (cancellous) bone • Network of bony rods w/ spaces • Found in epiphysis • Periosteum • Covers outer surface of bone • Endosteum • Lines the marrow cavity

  5. Microscopic Features of Bone - Cytology • Osteocytes • mature bone cells • recycle Ca in the bony matrix • help with bone repair • Osteoclasts • giant multinucleated cells that secrete acids and enzymes • Dissolve bony matrix • Release Ca • Osteoblasts • produce new bone (AKA osteogenesis) • Promotes Ca deposits in bone matrix

  6. Microscopic Features of Bone - Histology • Central canal • Contains blood vessels • Osteocytes • Bone cells • Lacunae • Small pockets that house osteocytes • Canaliculi • Link lacunae to blood vessels

  7. Microscopic Features of Bone - Compact vs. Spongy Bone Compact Bone Spongy Bone Haversian system (AKA osteons) Trabecule – rods that form arranged in circles networks (NO osteons!)

  8. Bone Formation & Growth • Begins 6 weeks after fertilization, stops around age 25 • Ossification – process of tissue replacement by bone • Intramembranous Ossification – bone develops within membranes of connective tissues • Ex: Cranial bones & clavicle • Endochondrial Ossification – bones replace cartilage • Ex: all bones except cranial bones & clavicle • Calcification – deposition of calcium salts • can also happen in other tissues, not just bone • Requirements: • Prenatal – minerals absorbed from mother (loses bone mass) • Consume Ca and P from diet • Vitamin D3 allows absorption of Ca and P • Vitamins A and C needed for osteoblast activity • http://www.youtube.com/watch?v=6f90506PvS8&feature=related

  9. Bone Remodeling • Remodeling – the removal and replacement of protein & minerals from bone • Heavily stressed bones become thicker and stronger • Inactivity (even brief) causes atrophy (regeneration)

  10. Homeostasis & Mineral Storage • 99% of bodily calcium is deposited in the skeleton • Nervous & muscular systems use Ca+ ions • Ca+ concentration is heavily regulated • Parathyroid hormone (PTH) – elevates Ca+ levels in body fluids • Bones become weaker • Calcitonin - depresses Ca+ levels in body fluids • Bones become stronger • These hormones work together to maintain homeostasis!

  11. Injury & Repair • Fracture: any crack or a break in a bone • Bone repairs can vary between 4 months to over a year. • Fracture hematoma – large blood clot that closes off injured blood vessels • External and internal calluses – localized thickenings from mitotic divisions of bone cells http://www.youtube.com/watch?v=qVougiCEgH8&feature=related

  12. Classification of Fractures • Displaced (not aligned) or non-displaced • Reduction – realigns bones for proper healing • Complete (through) or incomplete • Linear (parallel) or transverse (perpendicular to bone) • Compound (sticking through the skin) or simple (closed)

  13. Type of Fractures • Comminuted – 3+ fragments • Compression – crushed • Most likely with vertebrae • Spiral – due to twisting • Common in athletes • Depression – skull • Greenstick – children • Partial break/bend

  14. Aging • Reduction in bone mass occurs between ages 30-40 • Women lose ~8% of skeletal mass per decade • Men lose ~3% per decade • Epiphyses, vertebrae, & jaws most vulnerable • Osteoporosis – great reduction in bone mass • Increase in osteoclast activity caused by smoking or a decrease in estrogen • Other causes: lack of Ca+ in diet, inactive lifestyle, some medications

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