LESSONS 10 11 ARTICULATION Articulations Body movement occurs at joints where two bones connect Joint Structure o Determines direction and distance of movement range of motion or ROM o Joint strength decreases as mobility increases The more stable the joint the less moveable it is Classification of Joints Functional classification is based on range of motion of the joint Structural classification relies on the anatomical organization of the joint Three Functional Classifications Synarthrosis immovable joint o Are very strong o Edges of bones may touch or interlock o Four types of synarthrotic 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 Synchondrosis Is a rigid cartilaginous bridge between two bones o Epiphyseal cartilage of long bones o Between vertebrosternal ribs and sternum Synostosis Fused bones immovable o Metopic suture of skull fuses two sides of frontal bone o Epiphyseal lines of long bones Amphiarthrosis slightly movable joint o More moveable than synarthrosis o Stronger than freely movable joint o Two types of amphiarthroses Syndesmosis Bones connected by ligaments Ex Tibia and fibula Symphysis bones separated by fibrocartilage Ex Pubic symphysis Synovial Joints Diarthrosis freely movable joints o At ends of long bones o Within articular capsules o Lined with synovial membrane Four Structural Classifications Bony synotoses synarthroses Fibrous sutures and gomphoses synarthroses syndesmoses amphiarthroses Cartilaginous synchondroses synarthroses and symphyses amphiarthroses Synovial only diarthroses Synovial Joints Articular Cartilages o Pad articulating surfaces within articular capsules Prevent bones from touching o Smooth surfaces lubricated by synovial fluid Consistency of heavy molasses Reduce friction Synovial Fluid o Contains slippery proteoglycans glycoproteins secreted by fibroblasts o Functions of synovial fluid Lubrication Articular cartilage act as sponge filled with fluid compression of it pushes some synovial fluid out Nutrient distribution fluid circulates s joint moves provides nutrients to chondrocytes Shock absorption Accessory Structures of Synovial Joints o Cartilages Cushion the joint Fibrocartilage pad called a meniscus or articular disc plural menisci o Fat pads o Ligaments o Tendons Adipose tissue superficial to the joint capsule Protect articular cartilages Support strengthen joints Sprain ligaments with torn collagen fibers Attach to muscles around joint Help support joint o Bursae singular bursa a pouch Packets of synovial fluid Cushion areas where tendons or ligaments rub Bursitis inflamed bursae causing pain can result from repetitive motion irritation trauma infection Factors that stabilize Synovial Joints Four factors that prevent injury by limiting range of motion o Collagen fibers joint capsules ligaments o Shape of the articulating surfaces and menisci o Presence of other bones muscles or fat pads o Tension in the tendons of articulating bones NOTE pain receptors are not found on the inside of the synovial joints Pain felt due to joint damage results from nerves that monitor the capsule ligaments and tendons Injuries of the Synovial Joints Dislocation luxation caused by extreme stress o Articulating surfaces forced out of position o Damages articular cartilage ligaments joint capsule o Shoulder joint most prone to this injury Subluxation o A partial dislocation o NOTE double jointed people have weakly stabilized joints that are prone to dislocation or partial dislocation Movements Three types of Dynamic Motion o Linear movement gliding o Angular movement o Rotation Planes axis of Dynamic Motion o Monaxial 1 axis forward backward o Biaxial 2 axes forward backward and side to side o Triaxial 3 axes forward backward side to side and angular Types of Movements at Synovial Joints Terms used describe o Plane or direction of motion o Relationship between structures Gliding Movement o Two surfaces slide past each other Ex Between carpal or tarsal bones and motion between the clavicle and sternum Angular Movement o Flexion Angular motion in the anterior posterior plane Reduces angle between elements o Extension Increases o Hyperextension Angular motion in the anterior posterior plane angle between elements Angular motion of extension past the anatomical position Ex Hyperextension of neck to look at ceiling Angular motion in the frontal plane Moves away from the longitudinal axis o Abduction o Adduction Angular motion in the frontal plane Moves toward the longitudinal axis o Circumduction Angular motion in a circular motion without rotation Types of Rotational Movements at Synovial Joints Rotation movement described with reference to the figure in the anatomical position o Relative to longitudinal axis of body o Left or right rotation o Medial rotation inwards internal rotation Rotates toward axis Ex Bend arm at elbow move hand to chest extend arm palm anterior rotate so arm and palm is medial o Lateral rotation outward external rotation Rotates away from axis Ex With bent arm at elbow move hand away from chest o Pronation o Supination Rotates forearm radius over ulna Forearm in anatomical position NOTE pronation and supination are not the same as medial rotation and lateral rotation respectively Special Movements Special Movements include specific articulations or unusual types of movements o Inversion twists sole of foot medially o Eversion twists sole of foot laterally o Dorsiflexion Flexion at ankle pointing toes up o Plantar flexion Extension at ankle pointing toes down o Opposition Thumb movement toward fingers or palm grasping o Reposition opposite of opposition o Protraction moves anteriorly in the horizontal plane pushing forward o Retraction Opposite of protraction moving posteriorly pulling back o Elevation moves in superior direction o Depression moves in inferior direction down o Lateral flexion bends vertebral column from side to up side Classification of Synovial Joints by Shape Gliding Flattened or slightly curved faces limited motion nonaxial o Ex Vertebrocostal joints Hinge Angular motion in a single plane monaxial o Ex Elbow knee and ankle joints Pivot Rotation only monaxial o Ex Atlanto axial joint and proximal radio ulnar joint Condylar Oval articular face within a depression motion in two planes biaxial o Ex Radiocarpal joint Saddle Two concave straddled biaxial o Ex First carpometacarpal joint
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