8 The Skeletal System: Articulations
Introduction The body cannot move without joints Movements are linked to the range of joint action Joints (arthroses) are connections between bones that may or may not permit movement Two bones may be in direct contact with each other or separated by: Cartilage Fluid Fibrous tissue
Introduction Joints are classified based on: Function Range of motion Structure Makeup of the joint
Classification of Joints Joints can be classified based on their range of motion (function) Synarthrosis Immovable Amphiarthrosis Slightly movable Diarthrosis Freely movable
Classification of Joints Synarthrosis (immovable joint) Sutures (joints found only in the skull) Bones are interlocked together Gomphosis (joint between teeth and jaw bones) Periodontal ligaments of the teeth Synchondrosis (joint within epiphysis of bone) Binds the diaphysis to the epiphysis Synostosis (joint between two fused bones) Fusion of the three coxal bones
Classification of Joints (examples) Synostosis
Classification of Joints Amphiarthroses (slightly movable joints) Syndesmosis (ligaments that connect two bones but limit their motion) Between the radius and ulna Between the tibia and fibula Symphysis (bones are separated by a wedge or pad of cartilage) Between the pubic bones of the two coxal bones
Classification of Joints (examples) symphysis syndesmosis
Classification of Joints Diarthroses (freely movable joints) Also called synovial joints Typically found at the ends of long bones Examples of diarthroses joints: Shoulder joint Elbow joint Knee joint TMJ
Classification of Joints (examples)
Classification of Joints Synovial joints All synovial joints have six basic characteristics A joint capsule (dense regular CT) The presence of articular cartilages A joint cavity with synovial fluid A synovial membrane Accessory structures (cartilage, ligaments, tendons, bursae sacs) Sensory nerves and blood vessels
Classification of Joints Accessory structures of synovial joints Accessory structures are: Menisci (fibrous cartilage) Ligaments Tendons Bursae sacs (fluidfilled pockets)
Classification of Joints Joints can be classified based on their makeup (structure) Bony fusion (fusion of the frontal bone) Fibrous joint (skull sutures) Cartilaginous joint (pubic symphysis) Synovial joint (ball and socket joints and hinge joints)
Table 8.2 A Structural Classification of Articulations
Articular Form and Function Types of movements: Linear movements Two bones gliding past each other carpal/carpal tarsal/tarsal clavicle/sternum Angular movements abduction/adduction flexion/extension
Figure 8.3ac Angular Movements Abduction Adduction Abduction Adduction Abduction Adduction Abduction Adduction Abduction/adduction Adduction Toward midline Adduction/abduction Abduction Away from midline
Figure 8.3b Angular Movements Flexion Extension Decrease angle Flexion Flexion Extension Extension Increase angle Flexion Extension Flexion/extension
Articular Form and Function Rotational movements pronation/supination Special movements inversion/eversion dorsiflexion/plantar flexion lateral flexion protraction/retraction opposition depression/elevation
Figure 8.4 Rotational Movements Head rotation Right rotation Left rotation Lateral (external) rotation Medial (internal) rotation Supination Pronation Supination Pronation
Figure 8.5a Special Movements Eversion Inversion Eversion/Inversion
Figure 8.5b Special Movements Dorsiflexion Plantar flexion Dorsiflexion/plantar flexion
Figure 8.5c Special Movements Lateral flexion
Figure 8.5d Special Movements Retraction Protraction Retraction/protraction
Figure 8.5e Special Movements Opposition
Figure 8.5f Special Movements Depression Elevation Depression/elevation
Articular Form and Function Structural Classification of Joints Plane joints (gliding joints) Nonaxial (glides only in one direction) Multiaxial (glides in all directions) Ex. Carpal/carpal Tarsal/tarsal Vertebrae/vertebrae Clavicle/sternum Hinge joints Flexion and extension Ex. Elbow and knee Pivot joints Rotational movements Ex. Atlas/axis
Figure 8.6 A Structural Classification of Synovial Joints (Part 1 of 6) Gliding Joint Manubrium Slight movement
Figure 8.6 A Structural Classification of Synovial Joints (Part 2 of 6) Hinge Joint Humerus Ulna Angular movement in a single plane
Figure 8.6 A Structural Classification of Synovial Joints (Part 3 of 6) Pivot Joint Atlas Axis rotation
Articular Form and Function Structural Classification of Joints Condylar joints Oval articular surface on one bone articulates with a depression on another bone Ex. Radius/capitulum Radius/carpals Phalanges/metacarpals Phalanges/metatarsals Saddle joints Biaxial joints that allow some circumduction Ex. Pollex/metacarpal Ball and socket joints Triaxial joints Ex. Shoulder joint Hip joint
Figure 8.6 A Structural Classification of Synovial Joints (Part 4 of 6) Condylar Joint Scaphoid Radius Ulna Angular motion
Figure 8.6 A Structural Classification of Synovial Joints (Part 5 of 6) Saddle Joint III II I Metacarpal of thumb Trapezium Extremely mobile
Figure 8.6 A Structural Classification of Synovial Joints (Part 6 of 6) Ball-and-Socket Joint Humerus Scapula All combination of movements
Aging and Articulations As we age, joints are subjected to wear and tear Rheumatism Pain and stiffness affecting the skeletal system, muscular system, or both Arthritis Includes all rheumatic diseases that affect synovial joints Damage to the articular cartilage
Bones and Muscles Musculoskeletal system The skeleton and muscles are structurally and functionally interdependent