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Introduction to the Skeletal System

  • The skeletal system consists of bones; not simply dead structures, but very much alive.

  • Awareness of the vascularity of bones is crucial since broken bones can lead to severe complications.

  • Nursing practices surrounding skeletal issues have evolved significantly over the last few decades.

The Dynamic Nature of Bones

  • Bones and muscles are dynamic structures that change over time.

  • Example: Broken leg with plaster shows muscle and bone thinning due to immobilization.

  • Historically, treatment of broken bones involved extensive immobilization, but current practices promote mobility to prevent complications (e.g., blood clots).

Blood and Bone Connection

  • Bones are essential for blood production (red blood cells, white blood cells, and platelets) via red bone marrow.

  • Osteoporosis is a significant concern; it causes increased porosity of bones, making them weaker and prone to fractures.

Functions of the Skeletal System

  1. Support:

    • Provides structure and support to the body.

  2. Protection:

    • Protects vital organs (e.g., brain and spinal cord).

  3. Movement:

    • Bones are attachment points for muscles, facilitating movement.

  4. Production of Blood Cells:

    • Bone marrow is where blood cells are produced.

  5. Mineral Storage:

    • Bones store 99% of the body’s calcium and phosphate; crucial for physiological functions.

Composition of Bone

  • Bone consists of collagen and minerals:

    • About 1/3 is collagen (organic, carbon-based).

    • About 2/3 is minerals (inorganic, non-carbon).

  • Bones contain both red (blood cell production) and yellow (lipid storage) bone marrow.

Bone Structure and Types

Bone Shapes

  • Long Bones:

    • Longer than wider (e.g., femur, humerus).

  • Short Bones:

    • Equal in length and width (e.g., carpals in the wrist).

  • Flat Bones:

    • Thin and curved (e.g., scapula, sternum).

  • Irregular Bones:

    • Don’t fit into other categories (e.g., vertebrae).

Internal Structure of Bone

  • Compact Bone:

    • Dense outer layer providing strength; has osteons (functional units).

  • Spongy Bone (Cancellous):

    • Lighter, porous structure with trabecular plates; contains marrow.

    • More susceptible to osteoporosis due to higher surface area.

Bony Regions and Surface Features

  • Bones possess various surface features for attachment points, blood vessels, and nerves:

    • Elevations (for muscle attachments), Depressions (for blood vessels/nerves), Grooves (for ligaments).

  • Example: Greater trochanter on the femur serves as a site for ligaments.

Bone Adaptation to Stress

  • Bones adapt dynamically based on mechanical stress through deposition of spongy and compact bone.

  • Spongy bone absorbs impact without breaking compact bone, showcasing a clever structural design.

Osteons and Bone Cells

  • Osteons: Cylindrical units in compact bone, aligned parallel to withstand stress.

    • Composed of lamellae (concentric rings of bone tissue) surrounding central canals (containing blood vessels and nerves).

  • Osteocytes: Bone cells residing in lacunae between lamellae, communicating through extensions of their plasma membranes.

Summary of Bone Dynamics and Health

  • Bones are multifunctional and vital for various biological processes, including blood cell production and mineral storage.

  • Understanding bone dynamics, composition, and connection to overall health (e.g., osteoporosis) is essential in nursing.