Articulations or Joints Articulation or Joint Place where two bones (or bone and cartilage) come together Arthrology = study of the joints Functions of joints Give the skeleton mobility Hold the skeleton together Structure correlated with movement

Classification of Joints Structural classes: based on type of connective tissue type that binds bones and whether or not a joint cavity is present Fibrous Cartilaginous Synovial Functional classes: based on degree of motion Synarthrosis: non-movable Amphiarthrosis: slightly movable Diarthrosis: freely movable

Fibrous Joints Characteristics Types: United by fibrous connective tissue Have no joint cavity Move little or none Types: Sutures Syndesmoses

Fibrous Joints: Syndesmoses Two bones joined by ligament Most moveable of fibrous joints Examples: radioulnar joint and tibiofibular joints

Cartilaginous Joints Bones are joined by cartilage Lack a joint cavity Types Synchondroses: bound by hyaline cartilage Symphyses: bound by fibrocartilage

Cartilaginous Joints: Synchondroses Joined by hyaline cartilage Little or no movement Some are temporary and are replaced by synostoses Some are permanent Some like costochondral joints develop into synovial joints Examples: Epiphyseal plates, 1st sternocostal

Cartilaginous Joints: Symphyses Fibrocartilage uniting two bones Slightly movable Examples: symphysis pubis, between the manubrium and the body of the sternum, intervertebral disks.

Synovial Joints Contain synovial fluid in a joint cavity called the synovial cavity Allow considerable movement (diarthroses) Most joints that unite bones of appendicular skeleton reflecting greater mobility of appendicular skeleton compared to axial

Structure of Synovial Joints Articular cartilage: Hyaline cartilage that covers epiphysis Absorbs compression of joint Joint cavity (synovial cavity) Unique to synovial joints Cavity is a potential space that holds small amount of fluid Synovial fluid: Viscous fluid similar to raw egg white A filtrate of blood from capillaries in synovial membrane Contains glycoprotein molecules secre-ted by fibroblasts Nerves in capsule help brain know position of joints (proprioception) Structure of Synovial Joints

Flexion and Extension Flexion: movement of a body part anterior or posterior to the coronal plane Extension: movement of a body part posterior or anterior to the coronal plane Dorsoflexion - foot lifted toward the shin Plantar flexion - pointing toes downward Abduction: movement away from the midline Adduction: movement toward the midline

Types of Synovial Joints: Plane Joints Plane or gliding joints Monaxial. One flat bone surface glides or slips over another similar surface Sometimes considered an amphiarthrosis Examples: intervertebral, intercarpal, intertarsal acromioclavicular, carpometacarpal, tarsometatarsal,

Hinge and Pivot Joints Hinge joints Pivot joints Monaxial Convex cylinder in one bone; corresponding concavity in the other Example: elbow, ankle, interphalangeal Pivot joints Monaxial. Rotation around a single axis. Cylindrical bony process rotating within a circle of bone and ligament Example: articulation between dens of axis and atlas (atlantoaxial), proximal radioulnar

Types of Synovial Joints: Saddle joints Each articular surface is shaped like a saddle; Trapeziometacarpal joint at base of the thumb

Ball-and-Socket and Ellipsoid Joints Smooth heispherical head fits within a cuplike depression Multiaxial Examples: shoulder and hip joints Condyloid (ellipsoid) joint Oval convex surface on one bone fits into a similarly shaped depression on the next Atlantooccipital joint (C1-C2) Metacarpophalangeal joints

The Knee Joint Most complex diarthrosis patellofemoral = gliding joint tibiofemoral = gliding with slight rotation and gliding possible in flexed position Joint capsule anteriorly consists of patella and extensions of quadriceps femoris tendon Capsule strengthened by extracapsular and intracapsular ligaments

Effects of Aging on Joints Tissue repair slows; rate of new blood vessel development decreases Articular cartilages wear down and matrix becomes more rigid Production of synovial fluid declines Ligaments and tendons become shorter and less flexible: decrease in range of motion (ROM) Muscles around joints weaken A decrease in activity causes less flexibility and decreased ROM