Y khoa, y dược - Joints: Part A

8 Joints: Part AJoints (Articulations)Articulation—site where two or more bones meetFunctions of joints:Give skeleton mobilityHold skeleton togetherFunctional Classification of Joints Based on amount of movement allowed by the jointThree functional classifications:Synarthroses—immovable Amphiarthroses—slightly movable Diarthroses—freely movableStructural Classification of Joints Based on material binding bones together and whether or not a joint cavity is presentThree structural classifications:FibrousCartilaginous Synovial Fibrous JointsBones joined by dense fibrous connective tissueNo joint cavityMost are synarthrotic (immovable)Three types:SuturesSyndesmosesGomphosesFibrous Joints: SuturesRigid, interlocking joints containing short connective tissue fibersAllow for growth during youthIn middle age, sutures ossify and are called synostosesFigure 8.1aDensefibrousconnectivetissueSutureline(a) Suture Joint held together with very short,interconnecting fibers, and bone edgesinterlock. Found only in the skull.Fibrous Joints: SyndesmosesBones connected by ligaments (bands of fibrous tissue)Movement varies from immovable to slightly movableExamples: Synarthrotic distal tibiofibular jointDiarthrotic interosseous connection between radius and ulna Figure 8.1bFibulaTibiaLigament(b) Syndesmosis Joint held together by a ligament.Fibrous tissue can vary in length, but is longer than in sutures.Fibrous Joints: GomphosesPeg-in-socket joints of teeth in alveolar socketsFibrous connection is the periodontal ligamentFigure 8.1cRoot oftoothSocket ofalveolarprocessPeriodontalligament(c) Gomphosis “Peg in socket” fibrous joint. Periodontalligament holds tooth in socket.Cartilaginous JointsBones united by cartilageNo joint cavityTwo types:SynchondrosesSymphysesCartilaginous Joints: SynchondrosesA bar or plate of hyaline cartilage unites the bonesAll are synarthroticFigure 8.2aEpiphysealplate (temporaryhyaline cartilagejoint)Sternum(manubrium)Joint betweenfirst rib andsternum(immovable)(a) SynchondrosesBones united by hyaline cartilageCartilaginous Joints: SymphysesHyaline cartilage covers the articulating surfaces and is fused to an intervening pad of fibrocartilageStrong, flexible amphiarthroses Figure 8.2bFibrocartilaginousintervertebraldiscPubic symphysisBody of vertebraHyaline cartilage(b) SymphysesBones united by fibrocartilageSynovial JointsAll are diarthroticInclude all limb joints; most joints of the bodySynovial JointsDistinguishing features:Articular cartilage: hyaline cartilageJoint (synovial) cavity: small potential spaceSynovial JointsDistinguishing features:3. Articular (joint) capsule: Outer fibrous capsule of dense irregular connective tissueInner synovial membrane of loose connective tissueSynovial JointsDistinguishing features:4. Synovial fluid: Viscous slippery filtrate of plasma + hyaluronic acid Lubricates and nourishes articular cartilageFigure 8.3PeriosteumLigamentFibrouscapsuleSynovialmembraneJoint cavity(containssynovial fluid)Articular (hyaline)cartilageArticularcapsuleSynovial JointsDistinguishing features:5. Three possible types of reinforcing ligaments:Capsular (intrinsic)—part of the fibrous capsuleExtracapsular—outside the capsuleIntracapsular—deep to capsule; covered by synovial membraneSynovial JointsDistinguishing features:6. Rich nerve and blood vessel supply:Nerve fibers detect pain, monitor joint position and stretchCapillary beds produce filtrate for synovial fluidSynovial Joints: Friction-Reducing StructuresBursae:Flattened, fibrous sacs lined with synovial membranes Contain synovial fluidCommonly act as “ball bearings” where ligaments, muscles, skin, tendons, or bones rub togetherFigure 8.4bCoracoacromialligamentSubacromialbursaCavity inbursa containingsynovial fluidBursa rollsand lessensfriction.Humerus headrolls medially asarm abducts.(b) Enlargement of (a), showing how a bursaeliminates friction where a ligament (or otherstructure) would rub against a boneHumerusresting HumerusmovingSynovial Joints: Friction-Reducing StructuresTendon sheath:Elongated bursa that wraps completely around a tendonFigure 8.4aAcromionof scapulaJoint cavitycontainingsynovial fluidSynovialmembraneFibrouscapsuleHumerusHyalinecartilageCoracoacromialligamentSubacromialbursaFibrousarticular capsuleTendonsheathTendon oflong headof bicepsbrachii muscle(a) Frontal section through the right shoulder jointStabilizing Factors at Synovial JointsShapes of articular surfaces (minor role)Ligament number and location (limited role)Muscle tone, which keeps tendons that cross the joint tautExtremely important in reinforcing shoulder and knee joints and arches of the footSynovial Joints: MovementMuscle attachments across a joint:Origin—attachment to the immovable boneInsertion—attachment to the movable boneMuscle contraction causes the insertion to move toward the originMovements occur along transverse, frontal, or sagittal planesSynovial Joints: Range of MotionNonaxial—slipping movements onlyUniaxial—movement in one planeBiaxial—movement in two planesMultiaxial—movement in or around all three planesSummary of Characteristics of Body JointsConsult Table 8.2 for:Joint namesArticulating bonesStructural classificationFunctional classificationMovements allowedTable 8.2 (1 of 4)Table 8.2 (2 of 4)Table 8.2 (3 of 4)Table 8.2 (4 of 4)Movements at Synovial JointsGlidingAngular movements:Flexion, extension, hyperextensionAbduction, adductionCircumductionRotationMedial and lateral rotationMovements at Synovial Joints4. Special movementsSupination, pronationDorsiflexion, plantar flexion of the footInversion, eversionProtraction, retractionElevation, depressionOppositionGliding MovementsOne flat bone surface glides or slips over another similar surface Examples:Intercarpal jointsIntertarsal jointsBetween articular processes of vertebraeFigure 8.5aGliding(a) Gliding movements at the wristAngular MovementsMovements that occur along the sagittal plane:Flexion—decreases the angle of the jointExtension— increases the angle of the jointHyperextension—excessive extension beyond normal range of motionFigure 8.5b(b) Angular movements: flexion, extension, and hyperextension of the neckHyperextensionExtensionFlexionFigure 8.5cHyperextensionFlexionExtension(c) Angular movements: flexion, extension, andhyperextension of the vertebral columnFigure 8.5dExtensionExtensionFlexionFlexion(d) Angular movements: flexion and extension at theshoulder and kneeAngular MovementsMovements that occur along the frontal plane:Abduction—movement away from the midlineAdduction—movement toward the midlineCircumduction—flexion + abduction + extension + adduction of a limb so as to describe a cone in spaceFigure 8.5eAbductionAdduction(e) Angular movements: abduction, adduction, andcircumduction of the upper limb at the shoulderCircumductionRotationThe turning of a bone around its own long axisExamples:Between C1 and C2 vertebraeRotation of humerus and femurFigure 8.5fLateralrotationMedialrotationRotation(f) Rotation of the head, neck, and lower limbSpecial MovementsMovements of radius around ulna:Supination (turning hand backward)Pronation (turning hand forward)Figure 8.6aSupination(radius and ulna are parallel)(a) Pronation (P) and supination (S)Pronation(radius rotatesover ulna)Special MovementsMovements of the foot:Dorsiflexion (upward movement) Plantar flexion (downward movement)Figure 8.6bDorsiflexionPlantar flexionDorsiflexionPlantar flexion(b) Dorsiflexion and plantar flexionSpecial MovementsMovements of the foot:Inversion (turn sole medially)Eversion (turn sole laterally)Figure 8.6cEversionInversion(c) Inversion and eversionSpecial MovementsMovements in a transverse plane:Protraction (anterior movement)Retraction (posterior movement)Figure 8.6dProtractionof mandibleRetractionof mandible(d) Protraction and retractionSpecial MovementsElevation (lifting a body part superiorly)Depression (moving a body part inferiorly)Figure 8.6eElevationof mandibleDepressionof mandible(e) Elevation and depressionSpecial MovementsOpposition of the thumbMovement in the saddle joint so that the thumb touches the tips of the other fingersFigure 8.6f(f) OppositionOpposition