9.1: Joints and Their Classification:Any point where two bones meet is called a joint whether they are mobile or immobileBony Joints (synostosis): an immobile joint formed when the gap between two bones ossifies and they become a single boneOssification of either a fibrous or cartilaginous jointFibrous Joint (syntharthosis): a point at which adjacent bones are bound by collagen fibers that emerge from one bone, across the space in between them, and penetrate into the otherSutures and gomphoses: fibers are very short and allow for little or no movementSutures: closely bind the bones of the skull to each otherSerrate sutures: wavy lines along which the adjoining bones firmly interlock with each other by their serrated margins like pieces of a jigsaw puzzleCoronal, sagittal, and lambdoidLap (squamous) suture: where two bones overlapping beveled edgesAppears to be smoothSquamous suture of temporal and parietalPlane (butt) sutures: straight nonoverlapping edges hBorder each otherIntermaxillary suture in the roof of mouthGomphoses: fibers that extend from the bone matrix of the jaw into tissueTeethPeriodontal ligamentSyndesmosis: fibers are longer and the attached bones are more mobileLength of fibers give joints more mobilityInterosseous membrane between radius and ulnaPronation and supinationCartilaginous (amphiarthrosis) joints: two bones are linked by cartilageSynchondroses: a joint which the bones are bound by hyaline cartilageGrowth plateFirst rib to the sternumSymphyses: two bones are joined by fibrocartilagePubic symphysisVertebraeSynovial (diarthosis) Joints: freely movable, most complex joints , most importantGeneral Anatomy: two bones covered with articular cartilageA layer of hyaline cartilage 2-3 mm thickJoint Cavity containing synovial fluidRich in albumin and hyaluronic acidJoint Capsule: a connective tissue that encloses the cavity and retains fluidOuter fibrous capsule: continuous with periosteum of adjoining boneInner synovial membrane: composed mainly of fibroblast-like cells that secrete the fluidArticular Disc: when fibrocartilage grows inward from the joint capsule and forms a pad between the articulating bones and the pad crosses the entire joint capsuleMenisci are found in the knee, but each one do not entirely cross the jointThey absorb shock and pressure, guide the bone across each other, and improve fit between bones, stabilize the jointAccessory Structures:Tendon: strip or sheet of tough collagenous connective tissue that attaches a muscle to boneStabilize jointLigament: attaches bone to boneBursa: fibrous sac filled with synovial fluid located between adjacent muscles where a tendon passes over a bone or between bone and skinCushion muscle, help tendons slide more easily over joints, and enhance the mechanical effects of a muscle by modifying direction a muscle pullsTendon sheaths: elongated cylindrical bursae wrapped around a tendonEnabled tendons to move back and forth freelyJoint and Lever Systems:Effort Arm: portion of a lever from the fulcrum to the point of effortResistance Arm: part from the fulcrum to the point of resistanceMechanical Advantage: ration output force to its input forceIf ratio is greater than 1.0 lever produces more force, but less distance or speedIf ratio is less than 1.0 then lever produces more speed or distance than forceFunction of a lever: produce speed, distance, or force of motionCan’t be done by one leverTypes of LeversA first-class lever is one with the fulcrum in the middle (EFR), such as a seesaw.A second-class lever has the resistance in the middle (FRE).A third-class lever, the effort is applied between the fulcrum and resistance (REF).Range of Motion: flexibility-- the degrees through which a joint can moveStructure of the articular surfaces of the bonesJoint movement is limited by the shapes of the bone surfacesStrength and tautness of ligaments and joint capsulesSome bone surfaces impose little if any limitation on joint movement.these bones are joined by ligaments that limit their movementAction of the muscles and tendons.Pairs of muscles oppose each other and moderate the speed and range of joint motionA resting muscle maintains a state of tension called muscle toneAxes of RotationA moving bone has a relatively stationary axis of rotation that passes through the bone in a direction perpendicular to the plane of movement.Degrees of Freedom:Multiaxial, biaxial, monoaxialClasses of Synovial Joints:Ball-and-socket joints: one bone (the humerus or femur) has a smooth hemispherical head that fits into a cuplike socket on the other (the glenoid cavity of the scapula or the acetabulum of the hip bone).Condylar (ellipsoid) joints: These joints exhibit an oval convex surface on one bone that fits into a complementary-shaped depression on the other.BiaxialRadiocarpal jointSaddle Joints: both bones have a saddle-shaped surface—concave in one direction (like the front-to-rear curvature of a horse's saddle) and convex in the other (like the left-to-right curvature of a saddle).BiaxialGives us opposable thumbsSternoclavicular jointPlane (gliding) joints: bone surfaces are flat or only slightly concave and convexCarpal bones in the wristBiaxial, limitedHinge Joint: These are essentially monaxial joints, moving freely in one plane with very little movement in any other, like a door hingeone bone has a convex that fits into a concave depression on the other boneulna and tibiaPivot Joints: These are monaxial joints in which a bone spins on its longitudinal axis.There are two principal examples: the atlantoaxial joint between the first two vertebrae, and the radioulnar joint at the elbow.Knee (tibiofemoral) Joint: largest and most complex diarthrosis of the bodyPrimarily a hinge joint but is capable of slight rotation and lateral glidingThe joint capsule encloses only the lateral and posterior aspects of the knee joint, not the anteriorAnterior aspect is covered by the patellar ligament and the lateral and medial patellar retinaculaThe joint cavity contains two C-shaped cartilages called the lateral and medial menisci joined by a transverse ligamentAbsorb shockThe posterior popliteal region of the knee is supported by two collateral ligaments that prevent the knee from rotating when the joint is extended—the fibular (lateral) collateral ligament and the tibial (medial) collateral ligament and two intracapsular ligaments (lie deep within the joint)-- called the anterior cruciate ligament (ACL) and posterior cruciate ligament