Bio25 Ch. 9 - Skeletal System: Articulation

Objectives

• Types of Joints:

  • Structural:

  • Fibrous

  • Cartilaginous

  • Synovial

  • Functional:

  • Synarthrosis

  • Amphiarthrotic

  • Diarthrotic

• Selected Joints:

  • Temporal

  • Elbow

  • Shoulder

  • Knee

  • Ankle

9.1 Classification of Joints

• Joints (articulations): Points where bones, cartilage, or teeth come together.

• Characteristics:

  • Weaker points in the skeleton but capable of resisting forces.

  • Classified by structure (composition) and function (movement).

• Arthrology: Study of joints.

Structural Classifications

1. Fibrous Joints:

   • Connected by dense connective tissue.

   • Generally immobile or slightly mobile.

2. Cartilaginous Joints:

   • Connected by cartilage.

   • Generally immobile or slightly mobile.

3. Synovial Joints:

   • Connected by ligaments, featuring a fluid-filled cavity.

Functional Classifications

1. Synarthroses: Immobile joints (fibrous or cartilaginous).

2. Amphiarthroses: Slightly mobile joints (fibrous or cartilaginous).

3. Diarthroses: Freely mobile joints (all synovial JOINTS).

9.2 Fibrous Joints

• Types:

  1. Gomphoses: Joints between teeth and jawbone.

  2. Sutures: Found in the skull, immovable.

  3. Syndesmoses: Slightly movable joints, e.g., between certain long bones.

• Connected by dense regular connective tissue

• immobile or only slightly mobile

9.3 Cartilaginous Joints

• Cartilaginous Joints: Cartilage between ends of articulating bones: no joint cavity

• Types:

  1. Synchondroses: Composed entirely of hyaline cartilage, immobile.

     

  2. Symphyses: Composed of fibrocartilage, Compression. slightly movable (e.g., pubic symphysis).

     

9.4a Synovial Joints

• Characteristics:

  • Freely mobile diarthroses featuring:

  • Articular capsule: Surrounds joints with two layers.

  • Synovial fluid: Lubricates and nourishes cartilage.

    • Lubricates articular cartilage

    • act as a shock absorber

    • nourished the chondrocytes

  • Articular cartilage: Reduces friction during movement. (Hyaline cartilage on bone surface)

  • Ligaments & nerves: Provide stability and feedback.

    • connect one bone to another

    • Extrinsic Ligament: physically separate from articular capsule.

    • Intrinsic Ligament: Located within the articular capsule, these ligaments help to connect bone ends and provide additional support during joint movement.

    • Tendons: dense regular connective tissue. Attach muscle to bone

      

Articular Capsule

• Outer Fibrous Layer: Composed of dense connective tissue to prevent bone separation.

• Inner Synovial membrane Layer: Synovial membrane that produces synovial fluid.

  

Additional Structures

• Bursae: Sac-like structures reducing friction.

  • contains synovial fluid

  • connected to or separate from joint cavity

• Fat pads: Protective packing material surrounding joints periphery.

• Tendon sheaths: Encase tendons in areas of potential friction.

  

• Sensory receptors and blood vessels

• numerous in synovial joints

• receptors detect pain stimuli.

• They also provide information about joint position and movement, contributing to proprioception, which is essential for coordinated movement

• Tendon sheath: Elongated bursae wrapped around tendons where friction is excessive

  • Common in wrist and ankle

Classification of Synovial Joints

• By Movement:

  • Uniaxial: Movement in one plane or axis

    • plane joint: flat articular surfaces

    • limited to (side to side gliding movements) in a single plane

    • ex: small ones of wrist and foot

  

  • UNIAXIAL:

    • Hinge Joint: Convex surface within concave depression

  

  • UNIAXIAL:

    • Pivot Joint: Rotational movement around a single axis.

    • Rotation on longitudinal axis, allowing for specific movements such as turning the head or pronating the forearm.

  

  • Biaxial: Movement in two planes or axes

    • Condylar Joint: Oval, convex surface articulating with concave surface, but NO ROTAATION

  

  • Biaxial:

    • Saddle Joint: Convex and Concave surface resemble saddle shape, Two directions: SOME ROTATION

    • EX: Thumb

• • Multiaxial: Movement in multiple planes or axes

    • Ball and Socket Joint

    • Permit movement in 3 planes

    • Freely mobile type: EX- Shoulder and Hip

• By Shape:

  • Plane

  • Hinge

  • Pivot

  • Condylar

  • Saddle

  • Ball-and-socket

9.5 Movements of Synovial Joints

Gliding Motion

• Surfaces slide over each other (e.g., intercarpal joints). Carpals or Tarsals

  • back and forth

  • side to side

Angular Motion

• Changes the angle between bones:

  • Flexion: Decreases angle.

  • Extension: Increases angle.

  • Abduction/Adduction: Movement away/closer to the midline.

  • Circumduction: Circular movement.

• ANTERIOR - POSTERIOR PLANE:

• Flexion: decreases the angle between bones

  • bring bones closer together

  • ex: bending fingers

    

• Extension: (Opposite of Flexion) Increases angle between articulating bones

  • ex: straightening fingers

    

• Hyperextension: Extension beyond normal rang of motion

  • Not normal motion, Can result in injury

    

• CORNAL PLANE

• Lateral Flexion: trunk of body moving in coronal plane laterally.

  • occurs between vertebrae in cervical and lumbar region.

• Abduction: Lateral movement of body part (away from midline)

• Adduction: towards midline

• Circumduction: Circular movement of a body part, combining flexion, extension, abduction, and adduction in a sequence that describes a cone shape.

Rotational Motion

• Bone rotates around its axis:

  • Medial: Turns anterior surface of bone medially

  • Lateral Rotation: turns anterior surface of the bone laterally, away from the midline of the body.

  • Pronation: medial rotation of forearm - palm of hand to posterior

  • Supination: lateral rotation of forearm - palm of hand to anterior

Special Movements

• Elevation/Depression: Up/down movements (e.g., mouth opening/closing).

  

• Eversion/Inversion: Foot movements.

  

• Protraction/Retraction: Forward/backward movements (e.g., jaw).

  

• Opposition/Reposition: Thumb movements.

  

• Dorsiflexion/Plantar Flexion: Upward/downward movements of the foot, crucial for walking and running.

  

9.6 Synovial Joints and Levers

• Biomechanics: Applying mechanical principles to biological systems.

• Levers: Composed of a

  • fulcrum (pivot point), between effort and resistance

  • effort (force),

  • resistance (load).

• 

Types of Levers

1. First-Class Lever: Fulcrum is between effort and resistance (e.g., neck).

   

2. Second-Class Lever: Resistance is between fulcrum and effort (e.g., standing tiptoe).

   

3. Third-Class Lever: Effort applied between fulcrum and resistance (e.g., elbow).

   

9.7 Knee Joint

• Largest Diarthrosis: Primarily a hinge joint that allows slight rotation and gliding.

• Composed of 2 separate articulations

  • Tibiofemoral joint: between condyles of femur and condyles of tibia

  • Patellofemoral joint: between patella and patellar surface of femur

Structures of the Knee

• Support and Stabilization:

  • Quadriceps femoris muscle tendon: Passes over knee’s anterior surface, surrounds patella

  • Patellar ligament: extends rom patella to tibial tuberosity

  • Fibular Collateral ligaments (fibular & tibial) reinforce lateral surface of joint

  • Menisci: C-shaped cartilages for cushioning.

  • Cruciate ligaments: ACL and PCL preventing excessive movements.

9.8 Joint Aging and Health

• Arthritis: Group of conditions characterized by joint inflammation and degeneration.

  • Types include

  • Osteoarthritis: Degenerative joint conditions in older ppl

  • Gouty Arthritis: Inflammation due to high lvl of uric acid

  • Rheumatoid Arthritis: Autoimmune disorder causing joint inflammation and pain, often affecting both sides of the body symmetrically.

• Joint Health:

  • Regular exercise enhances joint health but may exacerbate pre-existing conditions.

Clinical Notes

• Injuries: Common injuries include collateral ligament injuries, sprains, Pott fractures, and meniscal tears.