Chapter 6: Skeletal System

SKELETAL SYSTEM SUMMARY

  • Definition

    • Composed of bones and cartilage; bones are living organs.

  • Functions (SPAM-BT)

    • S: Support
    • P: Protection
    • A: Assist movement
    • M: Mineral storage (Ca++, P)
    • B: Blood cell production (RBC, WBC, platelets)
    • T: Triglyceride storage (yellow marrow)

  • Bone Types (By Shape)

    • Long, Short, Flat, Irregular, Sesamoid, Sutural

  • Long Bone Structure

    • Diaphysis: Shaft
    • Epiphysis: Ends
    • Metaphysis: Between
    • Epiphyseal plate: Growth in length
    • Medullary cavity: Marrow space
    • Periosteum: Outer covering (growth + repair)
    • Endosteum: Inner lining

  • Bone Cells (GO BOOM)

    • G: Osteogenic (stem cells)
    • O: Osteoblasts (build bone)
    • O: Osteocytes (maintain bone)
    • M: Osteoclasts (melt bone / resorption)

  • Compact vs Spongy Bone

    • Compact: Dense, 80%, has osteons (central canal, lamellae, lacunae, canaliculi)
    • Spongy: Trabeculae, no osteons, lightweight, houses red marrow

  • Bone Formation (Ossification)

    • Intramembranous: Flat bones
    • Endochondral: Most bones (cartilage template)
    • Length growth: Epiphyseal plates (until ~25 yrs)
    • Thickness growth: Appositional growth

  • Bone Growth Control

    • Minerals: Calcium + Phosphorus (most important)
    • Vitamins: C, K, B12, A
    • Hormones: GH, Thyroid, Insulin, Estrogen, Androgen
    • Estrogen closes epiphyseal plates

  • Fractures

    • Types: Open, Closed, Comminuted, Greenstick, Impacted, Pott’s, Colles’, Stress
    • Repair Steps:
    1. Hematoma
    2. Fibrocartilage callus
    3. Bony callus
    4. Remodeling

  • Remodeling & Exercise

    • Bone constantly breaks down and rebuilds; must balance formation and resorption.
    • Weight-bearing exercise leads to stronger bones; lack of stress causes bone atrophy.