THE SKELETAL SYSTEM: THE JOINTS

The following topics will be discussed in this unit: Joint ClassificationsFibrous JointsCartilaginous JointsSynovial JointsTypes of Movements at Synovial JointsTypes of Synovial JointsFactors Affecting Contact and Range of Motion at Synovial JointsSelected Joints of the BodyAging and JointsArthroplasty

Joints (Joint Classification)The structural classification of jointsFibrous joints (bones held together by dense collagen fibers)Cartilaginous joints (bones held together by cartilage)Synovial joints (bones held together by ligaments)The functional classification of jointsSynarthrosis (an immovable joint)Amphiarthrosis (a slightly movable joint)Diarthrosis (a freely movable joint)

Joints (Fibrous Joints)Lack a synovial cavityThe articulating bones are held very closely together by dense irregular connective tissueFibrous joints permit little or no movementThree types of fibrous jointsSuturesSyndesmosesGomphoses

Joints (Fibrous Joints)SuturesOccur only between bones of the skullSyndesmosesPermits slight movementInterosseous membraneBetween the tibia and fibula in the legGomphosesImmovable jointJoint in which a cone-shaped peg fits into a socketArticulations of the teeth with the sockets of the maxillae and mandible

Joints (Cartilaginous Joints)Lacks a synovial cavityAllows little or no movementJoint is tightly connected by either cartilageTwo types of cartilaginous jointsSynchondrosesSymphyses

Joints (Cartilaginous Joints)SynchondrosesConnecting tissue is hyaline cartilageEpiphyseal (growth) plateSymphysesSlightly movable jointEnds of the articulating bones are covered with hyaline cartilage, but a disc of fibrocartilage connects the bonesPubic symphysisBetween the anterior surfaces of the hip bonesIntervertebral joints between the vertebrae

Joints (Synovial Joints)Synovial cavity allows a joint to be freely movableLigaments hold bones together in a synovial jointArticular CapsuleA sleeve-like capsule encloses the synovial cavityThe articular capsule is composed of two layersan outer fibrous capsulean inner synovial membraneSynovial FluidThe synovial membrane secretes synovial fluidFunctions to reduce friction by:lubricating the jointabsorbing shockssupplying oxygen and nutrients to the cartilageremoving carbon dioxide and metabolic wastes from the cartilage

Joints (Synovial Joints)

Joints (Synovial Joints)Accessory Ligaments and Articular Discs

Collateral ligaments of the knee joint

Anterior and posterior cruciate ligaments of the knee joint

MenisciPads of cartilage lie between the articular surfaces of the bonesAllow bones of different shapes to fit together more tightly

Joints (Synovial Joints)Bursae and Tendon SheathsBursaeSac-like structures containing fluid similar to synovial fluidLocated between tendons, ligaments and bonesCushion the movement of these body partsTendon sheathsWrap around tendonsReduce friction at joints

Joints (Types of Movements at Synovial Joints)Specific terminology is used to designate the movements that occur at jointsMovements are grouped into four main categories:1) Gliding2) Angular movements3) Rotation4) Special movements

Joints (Types of Movements at Synovial Joints)GlidingSimple movement back-and-forth and from side-to-sideThere is no significant alteration of the angle between the bonesLimited in rangeIntercarpal jointsAngular MovementsIncrease or a decrease in the angle between articulating bonesAngular movements includeFlexionExtensionLateral flexionHyperextensionAbductionAdductionCircumduction

Joints (Types of Movements at Synovial Joints)FlexionDecrease in the angle between articulating bonesBending the trunk forward ExtensionIncrease in the angle between articulating bonesFlexion and extension are opposite movementsLateral flexion Movement of the trunk sideways to the right or left at the waistHyperextensionContinuation of extension beyond the normal extensionBending the trunk backward AbductionMovement of a bone away from the midlineMoving the humerus laterally at the shoulder jointAdductionMovement of a bone toward the midlineMovement that returns body parts to normal position from abduction

Joints (Types of Movements at Synovial Joints)CircumductionMovement of a body part in a circleMoving the humerus in a circle at the shoulder jointRotationA bone revolves around its own longitudinal axisTurning the head from side to side as when you shake your head no

Joints (Types of Movements at Synovial Joints)

Joints (Types of Movements at Synovial Joints)Special MovementsElevationDepressionProtractionRetractionInversionEversionDorsiflexionPlantar flexionSupinationPronationOpposition

Joints (Types of Movements at Synovial Joints)ElevationUpward movement of a part of the bodyClosing the mouthIts opposing movement is depressionDepressionDownward movement of a part of the bodyOpening the mouthProtractionMovement of a part of the body anteriorlyThrusting the mandible outwardIts opposing movement is retractionRetractionMovement of a protracted part of the body back to normal

Joints (Types of Movements at Synovial Joints)InversionMovement of the foot mediallyIts opposing movement is eversionEversionMovement of the sole laterallyDorsiflexionBending of the foot at the ankle in an upward directionIts opposing movement is plantar flexionPlantar flexionBending of the foot at the ankle in a downward directionSupinationMovement of the forearm so that the palm is turned upwardIts opposing movement is pronationPronationMovement of the forearm so that the palm is turned downwardOppositionMovement of the thumb in which the thumb moves across the palm to touch the tips of the fingers on the same hand

Joints (Types of Synovial Joints)Synovial joints are classified based on type of movementPlanarHingePivotCondyloidSaddleBall-and-socket

Joints (Types of Synovial Joints)Planar JointsPrimarily permit back-and-forth and side-to-side movementsIntercarpal jointsHinge JointsProduce an opening and closing motion like that of a hinged doorPermit only flexion and extensionKnee and elbow

Joints (Types of Synovial Joints)Pivot JointsSurface of one bone articulates with a ring formed partly by another boneJoints that enable the palms to turn anteriorly and posteriorlyCondyloid JointsThe projection of one bone fits into the oval-shaped depression of another boneWrist

Joints (Types of Synovial Joints)Saddle JointsArticular surface of one bone is saddle-shaped, and the articular surface of the other bone fits into the saddleThumbBall-and-Socket JointsBall-like surface of one bone fitting into a cuplike depression of another boneShoulder and hip

Joints (Selected Joints of the Body)The selected joints described are:Temporomandibular jointShoulder jointElbow jointHip jointKnee joint

Joints (Selected Joints of the Body)Temporomandibular JointCombined hinge and planar joint formed by the mandible and the temporal boneOnly movable joint between skull bonesOnly the mandible moves

Joints (Selected Joints of the Body)Shoulder JointBall-and-socket joint formed by the head of the humerus and the scapulaMore freedom of movement than any other joint of the body

Joints (Selected Joints of the Body)Elbow JointHinge joint formed by the humerus, the ulna, and the radius

Joints (Selected Joints of the Body)Hip JointBall-and-socket joint formed by the femur and the hip bone

Joints (Selected Joints of the Body)Knee JointLargest and most complex joint of the bodyModified hinge joint

Joints (Selected Joints of the Body)Knee Joint

Joints (Aging and Joints)AgingMay result in decreased production of synovial fluidThe articular cartilage becomes thinnerLigaments shorten and lose some of their flexibilityOsteoarthritis is partially age-relatedStretching and aerobic exercises are helpful in minimizing the effects of agingHelp to maintain the effective functioning of ligaments, tendons, muscles, synovial fluid, and articular cartilage

Joints (Arthroplasty)ArthroplastyJoints may be replaced surgically with artificial jointsMost commonly replaced are the hips, knees, and shouldersHip ReplacementsPartial hip replacements involve only the femurTotal hip replacements involve both the acetabulum and head of the femurKnee ReplacementsActually a resurfacing of cartilage and may be partial or totalPotential complications of arthroplasty include infection, blood clots, loosening or dislocation of the replacement components, and nerve injury

Joints (Arthroplasty)

Joints (Arthroplasty)