Skeletal System Articulations

Skeletal System Articulations

• Articulations are the junctions between bones.
• Articulations are classified by their structure and function.
• Bony Fusion (Synostosis): A fusion of bones, considered a non-moving joint (Synarthrosis), example: frontal suture fusion.
• Fibrous Joint: Bones united by fibrous connective tissue, offering limited movement (Synarthrosis or Amphiarthrosis). Subtypes include suture (skull sutures), gomphosis (tooth in jaw), and syndesmosis (distal tibia-fibula joint).
• Cartilaginous Joint: Bones united by cartilage, providing slight movement (Synarthrosis or Amphiarthrosis). Types include synchondrosis (epiphyseal plates) and symphysis (pubic symphysis).
• Synovial Joint: Characterized by a synovial cavity, allowing free movement (Diarthrosis). Subtypes include monaxial (elbow), biaxial (wrist), and triaxial (hip, shoulder).

General Description of Articulations

• Joints are classified into three structural functional categories:

  • Synarthroses (no movement): bones held together tightly. Suture, gomphosis, synchondrosis, and synostosis exemplify this category.
  • Amphiarthroses (little movement): bones with limited movement. Syndesmosis and symphysis fit into this functional category.
  • Diarthroses (free movement): bones with substantial movement, like synovial joints.

• Synovial Joints: A joint containing a synovial cavity.

  • Essential structures: joint capsule, synovial membrane, articular cartilages, and joint cavity containing synovial fluid.

• Additional structures of synovial joints: Menisci (knee), articular discs (TMJ, sternoclavicular joint), and labra (shoulder).

Types of Movements

• Linear motion (Gliding): One bone slides against another. Example: intercarpal joints.
• Angular motion: Angles between bones change, with additional subtypes like:
  • Flexion: Bending a joint.
  • Extension: Straightening a joint.
  • Abduction: Movement away from the midline.
  • Adduction: Movement towards the midline.
• Circumduction: A circular movement of a limb.
• Rotation: Movement around an axis. Subtypes include medial (internal) and lateral (external) rotation.

Special Movements

• Additional movements beyond basic motions, including:
  • Eversion: Turning the sole of the foot outward.
  • Inversion: Turning the sole of the foot inward.
  • Dorsiflexion: Bending the foot upwards.
  • Plantar flexion: Bending the foot downward.
  • Lateral flexion: Side-to-side bending of the spine.
  • Retraction: Moving a part backward.
  • Protraction: Moving a part forward.
  • Depression: Lowering a body part.
  • Elevation: Raising a body part.
  • Opposition: Moving the thumb to touch other fingers.

Representative Articulations

• Temporomandibular Joint (TMJ): The joint connecting the mandible (lower jaw) with the temporal bone (skull). Includes specific structures like articular tubercle, articular surface, articular disc, condyloid process, and various ligaments.
• Sternoclavicular Joint: The articulation where the clavicle meets the sternum.
• Shoulder Joint: The glenohumeral joint, ball-and-socket type, high range of motion but less stable.

Problems with the Intervertebral Discs

• Slipped disc: Abnormal displacement of an intervertebral disc.
• Herniated disc: A bulge or rupture of the intervertebral disc.

Articulations of the Pelvis

• Includes several joints and ligaments, playing a critical role in the stability and mobility of the pelvic girdle. Key components include sacroiliac joint, pubic symphysis and numerous ligaments (Iliolumbar, sacrotuberous, sacrospinous etc.).

Articulations of the Thoracic Cage

• Costovertebral joints: between ribs and thoracic vertebrae.
• Sternocostal joints: between ribs and sternum.
• Costochondral joints: between ribs and costal cartilage.
• Interchondral joints: between costal cartilages.

Anatomy of the Knee, Elbow, and Ankle

• Detailed descriptions of the structures composing these joints, including bones, ligaments, and other connective tissues.

Radioulnar Joints

• Articulations between the radius and ulna, significant for forearm rotation.

The Joints of the Wrist

• Articulations between the radius/ulna and carpal bones.

Hip Joint

• Detailed anatomy of hip joint components including specific ligaments and cartilage structures.