BIO 2401 JOINTS page 1 JOINTS Joint articulation sites where 2 or more bones meet weakest part of skeleton Joint Functions mobility hold skeleton together Classification of Joints functional based on amount of movement allowed at joint 1 synarthroses immovable joints restricted to axial skeleton 2 amphiarthroses slight movable joints restricted to axial skeleton 3 diarthroses freely moving joints predominate in limbs structural based on material binding bones together and whether or not a joint cavity is present 1 fibrous bones joined by fibrous tissue no joint cavity present amount of movement is based on length of connective tissue fibers 3 types 2 cartilagenous bones joined by cartilage no joint cavity present 2 types 3 synovial bones are separated by a fluid filled joint cavity allows substantial free movement Structural Classification of Joints 1 fibrous joints a suture seams occur between bones of skull articulating bone edges interlock and junction is filled by short connective fibers that are continuous with periosteum are rigid splices that allow bone growth b syndesmosis bones are connected by ligaments connecting fibers are longer than in sutures to allow for give e g distal end of tibia and fibula attached by ligaments ligaments attaching radius and ulna c gomphoses peg in socket joints teeth 2 cartilaginous joints a synchrondrosis bar or plate of hyaline cartilage uniting bone totally immovable e g epiphyseal plates connecting diaphysis and epiphyses costal cartilage of 1st rib and manubrium b symphysis bones are covered with hyaline cartilage which fuses to intervening pad of fibrocartilage e g intervertebral joints and pubic symphysis BIO 2401 JOINTS page 2 3 synovial joints articulating bones are separated by fluid filled cavity e g all joints in limbs 4 structures common to all synovial joints 1 articular cartilage hyaline is spongy absorbs compression placed on joint thus keeps bones from being crushed at their ends 2 joint synovial cavity filled with synovial fluid 3 articular capsule 2 layered external layer is tough fibrous capsule dense irregular tissue and is continuous with periostea of articulating bones internal layer is a synovial membrane loose connective tissue 4 synovial fluid filtrate of blood that is viscous becomes less viscous with joint activity because fluid is warmed up provides slippery weight bearing film that reduces friction between cartilages is forced from cartilages when joint is compressed and seeps back as pressure is released contains phagocytic cells that clean up cellular debris 5 other structures found in many synovial joints reinforcing ligaments reinforces and strengthens can be intrinsic part of fibrous capsule or extracapsular can also be intracapsular and covered with synovial membrane bursae flattened fibrous sacs lined with synovial membrane contain a thin film synovial fluid common in sites where ligaments muscles skin tendons or bones rub together tendon sheath elongated bursae that wraps completely around a tendon subjected to friction Types of Movement in Synovial Joints 1 gliding simplest movement one flat bone surface glides over another similar surface e g intercarpal and intertarsal joints articular processes of vertebrae 2 flexion bending movement decreases angle of joint and brings bones close together usually over a sagittal plane e g bending knee or body trunk bending head forward on chest 3 extension reverse of flexion increases angle between articulating bones can hyperextend bending back beyond upright position 4 abduction movement of a limb away from midline along frontal plane e g raising arm or thigh laterally or spreading toes 5 adduction opposite of abduction movement of a limb toward body midline 6 circumduction moving a limb so it describes a cone in space distal end moves in circle while point of cone proximal end remains stationary consists of flexion abduction extension and adduction performed in succession 7 rotation turning of a bone around its long axis can be medial or lateral e g movement between first 2 cervical vertebrae and at hip and shoulder joints 8 supination refers to movements of the radius around the ulna ulna and radius are parallel to each other defines anatomical position 9 pronation refers to movement of the radius around the ulna radius is rotated over ulna weaker movement than supination is position when palm faces downward or posteriorly BIO 2401 10 11 12 13 14 15 16 JOINTS page 3 inversion special movement of foot sole of foot turns medially eversion special movement of foot sole of foot turns laterally protraction nonangular anterior movement in a transverse plane e g jutting out of jaw retraction nonangular posterior movement in a transverse plane e g moving jaw back to original position after jutting it out elevation lifting a body part superiorly e g chewing depression moving an elevated body part inferiorly e g chewing opposition thumb only results because of saddle joint between metacarpal 1 and carpals Types of Synovial Joints 6 major categories 1 plane articulating surfaces are flat allow only short slipping or gliding movements nonaxial joints e g joints between vertebral articular processes and intercarpal intertarsal joints 2 hinge motion is along a single plane like a hinge occurs when a cylindrical projection of 1 bone fits into a trough shaped surface on another bone permits flexion and extension only e g bending and straightening elbow and interpharyngeal joints 3 pivot movement is uniaxial rotation of one bone around its own long axis occurs when rounded end of one bone protrudes into a sleeve or ring of another e g joint between atlas and dens of axis rotation of radius around ulna at proximal end 4 condyloid ellipsoidal joint oval articular surface of one bone fits into complementary depression in another both articular surfaces are oval permits all angular motions flexion extension abduction adduction e g metacarpophalangeal or knuckle joint radiocarpal or wrist joint 5 saddle each articular surface has both concave and convex areas articular surfaces fit together concave to convex surfaces e g carpometacarpal joints of thumb allows twiddling of thumbs 6 ball and socket spherical or hemispherical head of one bone articulates with cuplike socket of another most freely moving joints in all axes and planes including rotation e g shoulder and hip joints Joint Disorders 1 bursitis inflammation of a bursa excessive fluid accumulates usually caused by a blow or