Skeletal System Function and Movement

Joint Structure and Function

• Joint Capsule: Extension of periosteum, encases the joint.
• Synovial Membrane: Moist, slippery membrane lining the capsule; secretes synovial fluid for lubrication.
• Joint Cavity: Small space between articular cartilage surfaces.
• Bursa: Small extensions of synovial membrane cushioning tendons over joints.

Types of Movement

• Abduction: Movement away from the body's midline.
• Adduction: Movement towards the body's midline.
• Extension: Increased angle between bones, increasing the size of a joint angle.
• Hyperextension: Extension beyond the anatomical position (normal range of motion).
• Flexion: Decreased angle between bones, decreasing the size of a joint angle.
• Supination: Turning the palm upward.
• Pronation: Turning the palm downward.
• Depression: Lowering a part of the body.
• Elevation: Raising a part of the body.
• Rotation: Pivoting around an axis.

Skeletal System Functions

• Support: Provides a framework for the body.
• Protection: Bones enclose and protect internal organs.
• Movement: Acts as levers for muscle action, with joints serving as fulcrums.
• Mineral Reservoir: Stores calcium and phosphorus.
• Hematopoiesis: Blood cell formation in red bone marrow.

Skeletal System Components

• Bones: Main structural part of the skeleton.
• Cartilage: Cushions and connects some bones.
• Joints: Connections between bones (movable and immovable).
• Ligaments: Flexible connections between bones.

Bone Classification

• Long Bones: Extended axis, enlarged ends (e.g., femur, humerus).
• Short Bones: Cubed or box-shaped (e.g., tarsals, carpals).
• Flat Bones: Broad, thin, flattened (e.g., scapula, ribs).
• Irregular Bones: Odd shapes and sizes (e.g., vertebrae, patella).

Number of Bones

• 206 bones in the human body.

Types of Joints

Synarthrotic Joints (Fibrous)

• Syndesmoses: Fibrous bonds (e.g., between tibia and fibula).
• Sutures: Thin layer of fibrous tissue (e.g., between skull bones).
• Gomphoses: Fibrous tissue (e.g., between teeth and mandible).

Amphiarthrotic Joints (Cartilaginous)

• Synchondroses: Costal cartilage (e.g., between ribs and sternum).
• Symphyses: Pad or disk of cartilage (e.g., between pubic bones).

Diarthrotic Joints (Synovial)

• Freely movable joints.

Non-Inflammatory Joint Disorders

• Osteoarthritis: Degenerative joint disease.
• Dislocation: Traumatic misalignment of a joint.
• Sprain: Damage to ligaments.

Inflammatory Joint Disorders

• Rheumatoid Arthritis: Autoimmune disease affecting synovial membrane.
• Juvenile Rheumatoid Arthritis: More severe form in children.
• Gouty Arthritis (Gout): Crystal formation due to uric acid buildup.

Bone Structure

• Diaphysis: Shaft portion of long bones.
• Compact Bone: Solid bone, provides support.
• Spongy Bone: Needle-like pieces, supports weight.
• Red Marrow (Myeloid Tissue): Dominant in infants, produces red blood cells.
• Yellow Marrow: Red marrow transformed with fat in adults.
• Epiphyseal Plate: Growth plate for bone elongation.
• Articular Cartilage: Cushions joints.
• Periosteum: White fibrous membrane covering bone (with blood vessels).
• Medullary Cavity: Hollow space in diaphysis, houses yellow marrow.
• Endosteum: Thin epithelial tissue lining the medullary cavity.