BIO 233 Chapter 9 Lecture Notes

233 Chapter 9
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
Classification of Joints
Two Methods of Classification
Functional classification is based on range of motion of the joint
Structural classification relies on the anatomical organization of the joint

Functional Classifications
Synarthrosis (immovable joint)
Amphiarthrosis (slightly movable joint)
Diarthrosis (freely movable joint)

Structural Classifications
Bony
Fibrous
Cartilaginous
Synovial


Classification of Joints
Synarthroses (Immovable Joints) - very strong, edges of bones may touch or interlock (4 types)
- Suture - Bones interlocked , Are bound by dense fibrous connective tissue, found only in skull
- Gomphosis - Fibrous connection (periodontal ligament), Binds teeth to sockets
- 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

Amphiarthroses (slightly movable joints), not much more than synarthroses,,
Stronger than freely movable joint (Two types)
Syndesmosis
Bones connected by ligaments
Symphysis
Bones separated by fibrocartilage

Diarthroses (Synovial joints) Also called freely movable joints
At ends of long bones
Within articular capsules (joint capsule)
Lined with synovial membrane

Articular Cartilages (Hyaline cart.)
- Pad articulating surfaces within articular capsules
- Prevent bones from touching
- Smooth surfaces lubricated by synovial fluid
- Reduce friction

Synovial Fluid - Contains slippery proteoglycans secreted by fibroblasts
Functions of synovial fluid
- Lubrication
- Nutrient distribution
- Shock absorption

, Synovial Joints (Accessory Structures)
Cartilages, Fat pads, Ligaments, Tendons, Bursae

Cartilages - Cushion the joint, Fibrocartilage pad (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

Tendons - Attach to muscles around joint, Help support joint

Bursae - Singular, bursa, a pouch (Pockets of synovial fluid)
Cushion areas where tendons or ligaments rub

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

Injuries
Dislocation (luxation) - Articulating surfaces forced out of position
Damages articular cartilage, ligaments, joint capsule
Subluxation - A partial dislocation

Movements - Three Types of Dynamic Motion
Linear movement (gliding)
Angular movement
Rotation

Planes (Axes) of Dynamic Motion
Monoaxial (1 axis)
Biaxial (2 axes)
Triaxial (3 axes)

Types of Movement at Synovial Joints
Terms describe: Plane or direction of motion, Relationship between structures
- Gliding movement - Two surfaces slide past each other (Between carpal or tarsal bones)
- Flexion - Angular motion, Anterior–posterior plane (Reduces angle at a joint)
- Extension - Angular motion, Anterior–posterior plane (Increases angle at a joint)
- Hyperextension - Angular motion (Extension past anatomical position)
- Abduction - Angular motion, Frontal plane (Moves away from longitudinal axis (body)
- Adduction - Angular motion, Frontal plane (Moves toward longitudinal axis (body)
- Circumduction - Circular motion without rotation, Angular motion

Types of Movement at Synovial Joints
Rotation - Direction of rotation from anatomical position, Relative to longitudinal axis of body
Left or right rotation
Medial rotation (inward rotation) Rotates toward axis
Lateral rotation (outward rotation) Rotates away from axis

Rotation -
Pronation - Rotates forearm, radius over ulna
Supination - Forearm in anatomical position