An Introduction to Joints Articulations



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Chapter 9

Joints

An Introduction to Joints

  • Articulations

  • Body movement occurs at joints (articulations) where two bones connect

  • Joint Structure

  • Determines direction and distance of movement (range of motion or ROM)

  • Joint strength decreases as mobility increases

9-1 Classification of Joints

  • Two Methods of Classification

  1. Functional classification is based on range of motion of the joint

  2. Structural classification relies on the anatomical organization of the joint

9-1 Classification of Joints

  • Functional Classifications

  • Synarthrosis (immovable joint)

  • Amphiarthrosis (slightly movable joint)

  • Diarthrosis (freely movable joint)

9-1 Classification of Joints

  • Structural Classifications

  • Bony

  • Fibrous

  • Cartilaginous

  • Synovial

9-1 Classification of Joints

  • Synarthroses (Immovable Joints)

  • Are very strong

  • Edges of bones may touch or interlock

  • Four types of synarthrotic joints

  1. Suture

  2. Gomphosis

  3. Synchondrosis

  4. Synostosis

9-1 Classification of Joints

  • Suture

  • Bones interlocked

  • Are bound by dense fibrous connective tissue

  • Are found only in skull

  • Gomphosis

  • Fibrous connection (periodontal ligament)

  • Binds teeth to sockets

9-1 Classification of Joints

  • Synchondrosis

  • Is a rigid cartilaginous bridge between two bones

  • Epiphyseal cartilage of long bones

  • Between vertebrosternal ribs and sternum

  • Synostosis

  • Fused bones, immovable

  • Metopic suture of skull

  • Epiphyseal lines of long bones

9-1 Classification of Joints

  • Amphiarthroses

  • More movable than synarthrosis

  • Stronger than freely movable joint

  • Two types of amphiarthroses

  1. Syndesmosis

  • Bones connected by ligaments
  1. Symphysis

9-1 Classification of Joints

  • Synovial Joints (Diarthroses)

  • Also called movable joints

  • At ends of long bones

  • Within articular capsules

  • Lined with synovial membrane

9-2 Synovial Joints

  • Articular Cartilages

  • Pad articulating surfaces within articular capsules

  • Prevent bones from touching

  • Reduce friction

9-2 Synovial Joints

  • Synovial Fluid

  • Contains slippery proteoglycans secreted by fibroblasts

  • Functions of synovial fluid

  1. Lubrication

  2. Nutrient distribution

  3. Shock absorption

9-2 Synovial Joints

  • Accessory Structures

  • Cartilages

  • Fat pads

  • Ligaments

  • Tendons

  • Bursae

9-2 Synovial Joints

  • Cartilages

  • Cushion the joint

  • Fibrocartilage pad called a meniscus (or articular disc; plural, menisci)

  • Fat Pads

  • Superficial to the joint capsule

  • Protect articular cartilages

  • Ligaments

  • Support, strengthen joints

  • Sprain – ligaments with torn collagen fibers

9-2 Synovial Joints

  • Tendons

  • Bursae

  • Singular, bursa, a pouch

  • Pockets of synovial fluid

  • Cushion areas where tendons or ligaments rub

9-2 Synovial Joints

  • Factors That Stabilize Synovial Joints

  • Prevent injury by limiting range of motion

  • Collagen fibers (joint capsule, ligaments)

  • Articulating surfaces and menisci

  • Other bones, muscles, or fat pads

  • Tendons of articulating bones

9-2 Synovial Joints

  • Injuries

  • Dislocation (luxation)

  • Subluxation

  • A partial dislocation

9-3 Movements

  • Three Types of Dynamic Motion

  1. Linear movement (gliding)

  2. Angular movement

  3. Rotation

  • Planes (Axes) of Dynamic Motion

  • Monaxial (1 axis)

  • Biaxial (2 axes)

  • Triaxial (3 axes)




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