Human Anatomy - ch. 5 Joint and fractures

Overview

This lecture covers the structure, function, classification, and common disorders of joints and fractures, including definitions, types, and clinical significance.

Joint Terminology & Types

• A joint (articulation) is where two bones meet, allowing varying degrees of movement.
• Dislocation (luxation): bones at a joint are forced out of alignment.
• Subluxation: partial dislocation, joint surfaces slightly misaligned.
• Ankylosis: stiffness due to bones fusing, often from injury or disease.
• Bone spurs form with abnormal bone contact, causing pain and limiting movement.

Fractures: Classification & Types

• Closed (simple) fracture: bone breaks but does not pierce the skin.
• Open (compound) fracture: bone breaks through the skin; high infection risk.
• Incomplete fracture: bone cracks but stays in one piece.
• Complete fracture: bone breaks into two or more pieces.
• Displaced: bone ends no longer align; non-displaced: bone ends remain aligned.
• Fracture types: stress (hairline), greenstick (children, partial bend), epiphyseal (growth plate), transverse (straight across), oblique (diagonal), spiral (twisting), comminuted (≥3 pieces), avulsion (tendon pulls bone off), impacted (ends driven together), compression (bone is crushed), depression (bone pressed inward).

Specific Fractures & Clinical Notes

• Colles fracture: distal radius, "dinner fork" deformity, from falls.
• Scaphoid fracture: wrist bone, risk of avascular necrosis due to poor blood supply.
• Herniated disc: nucleus pulposus leaks out, compressing nerves, causing pain.
• Pathological fracture: bone breaks due to disease (e.g., osteoporosis).

Joint Classification: Structural & Functional

• Fibrous joints: joined by dense connective tissue; little/no movement (e.g., sutures, gomphosis, syndesmosis).
• Cartilaginous joints: joined by cartilage; hyaline (immovable, e.g., epiphyseal plate) or fibrocartilage (slightly movable, e.g., intervertebral discs, pubic symphysis).
• Synovial joints: freely movable (diarthrotic); have joint cavity and synovial fluid.

Synovial Joint Structure & Types

• Articular cartilage covers bone ends; synovial fluid lubricates and nourishes joint.
• Capsule made of fibrous tissue encloses joint; inner synovial membrane produces fluid.
• Meniscus/articular disc: fibrocartilage pad for shock absorption and stabilization.
• Types: plane (gliding), hinge (elbow), pivot (atlas/axis), condyloid (knuckles), saddle (thumb base), ball-and-socket (shoulder, hip).

Ligaments, Tendons, and Bursae

• Ligaments connect bone to bone; stabilize joints (slow healing).
• Tendons connect muscle to bone.
• Bursa: synovial fluid-filled sacs; reduce friction; bursitis is inflammation.

Common Joint Disorders

• Osteoarthritis: degeneration of cartilage, bone spurs, "wear and tear."
• Rheumatoid arthritis: autoimmune destruction of cartilage, joint deformity.
• Gout: uric acid crystal deposition, especially in big toe.
• Osteomalacia/rickets: bone softening, defective mineralization (often vitamin D related).
• Osteomyelitis: bone infection.
• Achondroplasia: genetic dwarfism, cartilage growth disorder.
• Chondromalacia patellae: softening of patellar cartilage.
• Paget's disease: excessive bone deposit, deformity.
• Ankylosing spondylitis: spinal fusion, reduced mobility.
• Synovitis: inflammation of synovial membrane.

Congenital Anomalies

• Polydactyly: extra digits (fingers/toes), usually non-functional.
• Syndactyly: fused digits, may be partial or complete, simple (soft tissue) or complex (includes bone); may occur as part of syndromes (e.g., Apert syndrome).

Key Terms & Definitions

• Dislocation (Luxation) — complete loss of alignment at a joint.
• Subluxation — partial loss of joint alignment.
• Ankylosis — fusion and stiffness of a joint.
• Bone Spur — abnormal bony growth at a joint.
• Closed Fracture — bone break without skin penetration.
• Open Fracture — bone break with skin penetration.
• Meniscus — cartilage pad in some synovial joints.
• Ligament — bone-to-bone connection.
• Tendon — muscle-to-bone connection.
• Bursa — lubricating sac between tissues.
• Osteoarthritis — degenerative joint disease.
• Rheumatoid Arthritis — autoimmune joint inflammation.
• Gout — joint inflammation from uric acid crystals.

Action Items / Next Steps

• Review lecture material and memorize types/classifications of joints and fractures.
• Study vocabulary: fibrous, cartilaginous, synovial, movements (synarthrotic, amphiarthrotic, diarthrotic).
• Complete assigned readings or watch recommended videos as directed in class.