Chapter+8+API

Chapter 08 Lecture Outline

  • This chapter focuses on the various types of joints and their movements in the human body, explaining the structural and functional classifications, along with specific examples of joint types.

8.1 Types of Joints

  • Joints (also known as articulations) are defined as:
    • Functional connections between bones.
    • Structures that bind parts of the skeletal system together.
    • Facilitators of bone growth.
    • Allowances for shape changes in the skeleton during childbirth.
    • Enablers of body movement in response to skeletal muscle contractions.

Structural Classification of Joints

  • Fibrous Joints:
    • Held together by dense connective tissue.
    • Found in bones that are in close contact.
  • Cartilaginous Joints:
    • Held together by cartilage.
  • Synovial Joints:
    • Feature a complex structure compared to fibrous or cartilaginous joints.

Functional Classification of Joints

  • Synarthrotic Joints:
    • Immovable joints.
  • Amphiarthrotic Joints:
    • Slightly movable joints.
  • Diarthrotic Joints:
    • Freely movable joints.

8.2 Types of Joints in Detail

Fibrous Joints

  • Definition:
    • Fibrous joints are held together with dense connective tissue that contains numerous collagen fibers.
    • They are typically found in bones that are in close proximity to each other.
Types of Fibrous Joints

  • Syndesmosis:

    • Bones are bound by a sheet of dense connective tissue (interosseous membrane) or a bundle of dense connective tissue (interosseous ligament).
    • Classified as amphiarthrotic (flexible, with a possible twisting movement).
    • Example: The joint between the tibia and fibula.

  • Suture:

    • A thin layer of connective tissue (sutural ligament) connects the bones.
    • Classified as synarthrotic (immovable).
    • Found between the flat bones of the skull.

  • Gomphosis:

    • Defined as a cone-shaped bony process fitting into a socket.
    • Also synarthrotic (immovable).
    • Example: The roots of teeth anchored within the maxilla or mandible by the periodontal ligament.

Cartilaginous Joints

  • Definition:
    • Cartilaginous joints are connected via hyaline cartilage or fibrocartilage.
Types of Cartilaginous Joints

  • Synchondrosis:

    • Comprises bands of hyaline cartilage uniting bones.
    • Classified as synarthrotic.
    • Types include temporary structures like the epiphyseal plate, which ossifies into a synostosis, and permanent structures like the joint between the manubrium and the first rib involving costal cartilages.

  • Symphysis:

    • Features a pad of fibrocartilage situated between the bones, with articular surfaces covered by hyaline cartilage.
    • Classified as amphiarthrotic (allowing limited movement).
    • Examples: The pubic symphysis and joints between adjacent vertebrae (intervertebral discs).

Synovial Joints

  • Definition:
    • Comprise the majority of joints in the body and are all classified as diarthrotic, allowing for a broad range of movement.
    • They possess a more complex structure when compared to fibrous or cartilaginous joints.
Structure of Synovial Joints
  • Components include:
    • Articular Cartilage:
    • Covers the articulating ends of bones.
    • Joint Capsule:
    • Composed of two layers:
      • Outer fibrous layer (composed of ligaments).
      • Inner synovial membrane, which secretes synovial fluid.
    • Synovial Cavity:
    • Space within the joint filled with synovial fluid, allowing for movement.
    • Ligaments:
    • Additional supportive structures.
    • Meniscus (-i):
    • Present in some joints, providing cushioning.
    • Bursa (-ae):
    • Fluid-filled sacs that reduce friction between tissues.
Types of Synovial Joints

  1. Ball-and-Socket Joint:

    • Also known as spheroidal joint.
    • Characterized by a round head in a cup-shaped cavity.
    • Provides the widest range of motion; multiaxial and allows rotation.
    • Examples: Hip and shoulder joints.

  2. Condylar Joint:

    • Also known as an ellipsoidal joint.
    • Features an oval condyle fitting into an elliptical cavity.
    • Allows back-and-forth and side-to-side movements; classified as biaxial with no rotation.
    • Example: Joints between metacarpals and phalanges.

  3. Plane Joint:

    • Also known as a gliding joint.
    • Characterized by almost flat or slightly curved surfaces.
    • Permits back-and-forth and twisting movements; nonaxial.
    • Examples: Wrist and ankle joints.

  4. Hinge Joint:

    • Features a convex surface fitting into a concave surface of another bone.
    • Allows uniaxial movement (in one plane).
    • Example: Elbow and joints between phalanges.

  5. Pivot Joint:

    • Also called a trochoid joint.
    • Characterized by a cylindrical surface that rotates within a ring of another bone.
    • Allows uniaxial movement (rotation only).
    • Example: Joint between the atlas (C1) and the dens of the axis (C2).

  6. Saddle Joint:

    • Also known as a sellar joint.
    • Both bones possess concave and convex surfaces.
    • Allows biaxial movement (in two planes).
    • Example: Joint between the carpal and metacarpal of the thumb.

8.3 Types of Joint Movements

  • Movements at synovial joints are primarily produced by the action of skeletal muscles.
  • Origin:
    • The relatively fixed end of a skeletal muscle.
  • Insertion:
    • The more movable end of a skeletal muscle.
  • Movement occurs when muscle fibers contract, pulling the insertion toward the origin.

Types of Joint Movements

  1. Flexion:
    • Bending of parts at a joint.
  2. Extension:
    • Straightening of parts at a joint.
  3. Hyperextension:
    • Extension beyond the normal anatomical position.
  4. Lateral Flexion:
    • Bending to the side.
  5. Abduction:
    • Movement away from the midline of the body.
  6. Adduction:
    • Movement toward the midline of the body.
  7. Dorsiflexion:
    • Ankle movement that points the toes upward.
  8. Plantar Flexion:
    • Ankle movement that points the toes downward.
  9. Circumduction:
    • Movement of a part of the body in a circular path.
  10. Rotation:
    • Movement around an axis:
    • Medial Rotation:
      • Movement toward the midline.
    • Lateral Rotation:
      • Movement away from the midline.
  11. Supination:
    • Forearm rotation so the palm faces upward or forward; in a supine position, the back faces down.
  12. Pronation:
    • Forearm rotation so the palm faces downward or backward; in a prone position, the back faces upward.
  13. Inversion:
    • Turning of the foot so the plantar surface faces the midline.
  14. Eversion:
    • Turning of the foot so the plantar surface faces away from the midline.
  15. Protraction:
    • Movement of a body part forward.
  16. Retraction:
    • Movement of a body part backward.
  17. Elevation:
    • Raising a body part.
  18. Depression:
    • Lowering a body part.

8.4 Examples of Synovial Joints

  • The chapter describes several major synovial joints, illustrating their structures and functions:

  1. Shoulder Joint:

    • Classification: Ball-and-socket.
    • Components: Head of humerus and the glenoid cavity of scapula.
    • Features:
      • Loose joint capsule.
      • Ligaments preventing displacement.
      • Presence of glenoid labrum and several bursae.
      • Major ligaments include:
      • Coracohumeral ligament.
      • Glenohumeral ligaments.
      • Transverse humeral ligament.
      • Wide range of motion including rotation and circumduction.

  2. Elbow Joint:

    • Contains two articulations:
      • Hinge Joint: Between the trochlea of humerus and the trochlear notch of ulna, allowing flexion and extension only.
      • Plane (Gliding) Joint: Between the capitulum of humerus and the fovea on the head of radius, permitting pronation and supination.
    • Major ligaments include:
      • Radial collateral ligament.
      • Ulnar collateral ligament.
      • Anular ligament.

  3. Hip Joint:

    • Classification: Ball-and-socket.
    • Components: Head of femur and the acetabulum of the hip bone.
    • Features:
      • Heavy joint capsule and acetabular labrum.
      • Numerous reinforcing ligaments including:
      • Iliofemoral ligament (strongest ligament in the body).
      • Pubofemoral ligament.
      • Ischiofemoral ligament.
      • Variety of movements, less extensive than the shoulder joint.

  4. Knee Joint:

    • The largest and most complex synovial joint.
    • Comprises three bones:
      • Femur (with medial and lateral condyles).
      • Tibia (with medial and lateral condyles).
      • Patella (articulating with the anterior surface of the femur).
    • Features:
      • Strengthened by numerous ligaments and tendons.
      • Cushioned by bursae and fat pads, with menisci separating femur and tibia.
      • Functions as a modified hinge joint with flexion, extension, and some rotation when flexed.
Ligaments of the Knee Joint
  • Major ligaments include:
    • Patellar ligament.
    • Oblique popliteal ligament.
    • Arcuate popliteal ligament.
    • Tibial (medial) collateral ligament.
    • Fibular (lateral) collateral ligament.
    • Anterior cruciate ligament.
    • Posterior cruciate ligament.

Clinical Applications

Clinical Application 8.1: Joint Disorders

  • Joint injuries can arise from:
    • Trauma, overuse, infections, inappropriate immune responses, or