Anatomy and Physiology I Lecture Review

Chapter 9: Joints

Synovial Joints

• Additional Structures:

  • Articular Discs and Menisci: Fibrocartilaginous structures in some synovial joints.

  • Articular Disc: Oval-shaped (e.g., sternoclavicular joint); unites bones & facilitates smooth movements (e.g., TMJ).

  • Meniscus: Larger and C-shaped (e.g., knee joint); aids in shock absorption and cushioning.

  • Fat Pads: Cushion impacts between bones in some synovial joints.

  • Bursae: Thin connective tissue sacs filled with fluid that reduce friction between bones and other structures.

  • Subcutaneous Bursae: Between skin and bone (prepatellar bursa, olecranon bursa).

  • Submuscular Bursae: Between muscle and bone (trochanteric bursa).

  • Subtendinous Bursae: Between tendon and bone (subacromial bursa).

  • Tendon Sheaths: Encapsulate tendons in joint crossings, hold lubricating fluid for smooth movement.

Types of Synovial Joints

1. Pivot Joint

   • Features rotating movement within a ring formed by a ligament and articulating bone.

   • Examples: Atlantoaxial (C1 and C2 vertebrae), proximal radioulnar joint.

2. Hinge Joint

   • Provides a uniaxial movement allowing flexion and extension.

   • Examples: Humeroulnar (elbow), tibiofemoral (knee).

3. Condyloid/Ellipsoid Joint

   • Offers biaxial movement with a shallow depression receiving a rounded bone end.

   • Examples: Metacarpophalangeal joints (knuckles), radiocarpal joint (wrist).

4. Saddle Joint

   • Allows biaxial movement where articulating ends are both convex and concave.

   • Examples: First carpometacarpal joint (thumb), sternoclavicular joint.

5. Plane Joint

   • Allows non-axial movement, permitting flat surfaces to glide over each other.

   • Examples: Intercarpal joints (hands), intertarsal joints (feet).

6. Ball-and-Socket Joint

   • Multiaxial joint providing the greatest range of motion, with a spherical head fitting into a socket.

   • Examples: Shoulder joint (glenohumeral), hip joint (femoroacetabular).

Classification of Joints

• Functional Classification:

  • Synarthrosis: Immovable joint (e.g., sutures).

  • Amphiarthrosis: Slightly movable joint (e.g., symphyses).

  • Diarthrosis: Freely movable joint (synovial) with various types of movement.

• Structural Classification:

  • Fibrous Joint: Joined by fibrous connective tissue.

  • Cartilaginous Joint: Joined by cartilage.

  • Synovial Joint: Complex joints with synovial fluid.

Aging and Joint Disorders

• Arthritis

  • Inflammation of synovial joints leading to pain, swelling, stiffness.

  • Osteoarthritis: Common in aging due to wear and tear.

  • Gout: Caused by uric acid crystal deposition; affects joints such as toe and knee.

Types of Body Movements

• Movement Descriptions:

  • Sagittal Plane: Flexion/Extension.

  • Frontal Plane: Abduction/Adduction, Inversion/Eversion.

  • Transverse Plane: Rotation (Medial/Lateral), Pronation/Supination.

Flexion and Extension

• Flexion: Decreases the angle of the joint (e.g., bending elbow).

• Extension: Increases the angle of the joint (e.g., straightening knee).

Movement Terms

• Hyperflexion and Hyperextension: Excessive ranges can lead to injuries.

• Abduction: Moves limb away from the body (e.g., raising arms).

• Adduction: Moves limb toward the body.

• Circumduction: Circular movement at joints (e.g., shoulder).

• Rotation: Implies twisting around an axis (e.g., neck movements).

• Dorsiflexion and Plantarflexion: Movements at the ankle.

Conclusion

Understanding the structure and function of joints, especially synovial joints, is integral for grasping the complexities of human movement and potential disorders associated with aging and other factors.