Skeletal System Notes

The Skeletal System

  • Axial vs Appendicular Skeleton

    • Axial Skeleton
    • Composed of the skull, vertebral column, and rib cage.
    • Provides support and protection for the brain, spinal cord, and thoracic organs.
    • Appendicular Skeleton
    • Includes bones of the limbs and girdles.
    • Facilitates movement and acts as an attachment for muscles.

  • Functions of Skeletal System

    • Protection: Shields vital organs (e.g., cranium protects the brain).
    • Attachment: Serves as anchor points for muscles, enabling movement.
    • Support: Provides structure to the body and maintains posture.
    • Storage: Stores minerals (e.g., calcium, phosphorus) and produces blood cells in the bone marrow.

  • Types of Bones

    • Long Bones: e.g., Femur, Humerus
    • Short Bones: e.g., Carpals, Tarsals
    • Flat Bones: e.g., Ribs, Cranium
    • Irregular Bones: e.g., Vertebrae
    • Sesamoid Bones: e.g., Patella

  • Structure of a Long Bone

    • Diaphysis: Long shaft with compact bone.
    • Epiphysis: Ends of the bone with spongy bone, covered by articular cartilage.
    • Articular Cartilage: Smooth surface at joints to reduce friction.
    • Bone Marrow Cavity: Contains bone marrow; produces blood cells.
    • Periosteum: Protective outer layer of the bone, including nerves and blood vessels.

  • Anatomical Terminology

    • Proximal: Closer to the center (e.g., shoulder is proximal to hand).
    • Distal: Further from the center (e.g., hand is distal to shoulder).
    • Medial: Closer to the midline (e.g., coccyx medial to carpals).
    • Lateral: Away from the midline (e.g., humerus lateral to sternum).
    • Inferior: Below (e.g., knees are inferior to shoulders).
    • Superior: Above (e.g., skull is superior to shoulders).
    • Anterior: In front (e.g., sternum anterior to vertebrae).
    • Posterior: Behind (e.g., vertebrae are posterior to sternum).

  • Functions of Connective Tissues:

    • Tendons: Attach muscles to bones.
    • Ligaments: Connect bones to bones at joints.
    • Cartilage: Cushions joints and reduces friction.

  • Definition of Joint: A joint is the anatomical point where two bones meet, allowing for varying degrees of movement.

  • Types of Joints:

    • Fibrous Joints: No movement allowed (e.g., sutures of the skull).
    • Cartilaginous Joints: Limited movement (e.g., vertebrae).
    • Synovial Joints: Freely moving joints allowing diverse movements (e.g., knee, shoulder).

  • Features of Synovial Joints:

    • Articular Cartilage: Protects bone ends at the joint.
    • Synovial Fluid: Lubricates the joint.
    • Synovial Membrane: Lines the joint capsule and produces synovial fluid.
    • Bursae: Fluid-filled sacs reducing friction.
    • Meniscus: Fibrocartilage pads providing cushioning.
    • Ligaments: Connective tissues stabilizing the joint.

  • Types of Synovial Joints:

    • Hinge Joints: e.g., elbow, knee (flexion/extension).
    • Ball and Socket Joints: e.g., shoulder, hip (multi-directional movement).
    • Pivot Joints: e.g., neck (rotation).
    • Condyloid Joints: e.g., wrist (multiple directions, no rotation).
    • Saddle Joints: e.g., thumb (complementary movements).
    • Gliding Joints: e.g., tarsals and carpals (sliding movements).

  • Types of Movements in Synovial Joints:

    • Flexion/Extension: Decrease/increase the angle at a joint.
    • Abduction/Adduction: Move a limb away/toward the body midline.
    • Pronation/Supination: Rotational movement of forearm.
    • Elevation/Depression: Move a structure superiorly/inferiorly.
    • Rotation/Circumduction: Turning a structure around its axis/complex circular movement.
    • Eversion/Inversion: Movement of the ankle; turning sole inward/outward.
    • Plantar/Dorsi Flexion: Foot movement; standing on toes/walking on heels.