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or articulations, are sites where 2 or more bones meet, weakest part of the skeleton, classified by structure and function. Less movable joints are more stable
Structural Classification of Joints
focuses on the material binding the bones together and whether or not a joint cavity is present. There are fibrous, cartilaginous, and synovial joints
bones are joined by fibrous tissue, namely dense fibrous connective tissue, and no joint cavity is present, mostly immovable. 3 types of fibrous joints (sutures, syndesmoses,and gomphoses)
seams; occur only between bones of the skull, Rigid, interlocking joints containing short connective tissue fibers
Allow for growth during youth, In middle age, sutures ossify and are called synostoses
bones are connected by ligaments, cords, or bands of fibrous tissue, Movement varies from immovable to slightly movable and depends on length and amount of fibers
(gomphosis)a peg-in-socket fibrous joint (ex: articulation of a tooth with its bony alveolar socket), Fibrous connection is the periodontal ligament
the articulating bones are united by cartilage, they lack joint cavity and not highly movable, 2 types of cartilaginous joints are synchondroses and symphyses
(synchondrosis)site where bar or plate of hyaline cartilage unites bone (ex: epiphyseal plate in children and coastal cartilage of first rib and manibrium of sternum)
articlar surfaces of the bones are covered with articular (hyaline) cartilage, and is fused to an intervening pad of fibrocartilage [acts as shock absorber cause resiliency], strong flexible amphiathroses
those in which the articulating bones are seperated by a fluid-containing joint cavity. All are diarthrotic, Include all limb joints; most joints of the body. 6 distinguishing features
2. Joint Cavity
a feature unique to synovial joints, space that contains small amount of synovial fluid
3. Articular Capsule
2 layers enclose the joint cavity. External layer is tough fibrous capsule (composed of dense irregular connective tissue) [strenghtens joint so that bones are not pulled apart. Inner layer is a synovial membrane (composed of loose connective tissue) [covers all internal joint surfaces that are not hyaline cartilage]
4. Synovial Fluid
slippery fluid which occupies all free spaces within the joint capsule. Lubricates joint surfaces and nurishes articular cartilage.
5. Reinforcing Ligaments
reinforce and strengthen synovial joints. Most often they are capsular, or intristic, ligaments [thickened part of fibrous capsule], Extracapsular (outside capsule) or Intracapsular (deep to capsule; covered by synovial membrane)
Nerves and Blood Vessels
Nerve fibers detect pain, monitor joint position and stretch, Capillary beds produce filtrate for synovial fluid
Flattened, fibrous sacs lined with synovial membranes , Contain synovial fluid, Commonly act as "ball bearings" where ligaments, muscles, skin, tendons, or bones rub together
Factors influencing Stability of Synovial Joints
shapes of the articular sirface, the number and positioning of ligaments, and muscle tone
unite the bones and prevent excessive or undesirable motion (more ligaments joint have the stronger)
which keeps tendons that cross the joint taut, extremely important in reinforcing the shoulder and knee joints and the arches of the foot
attachment of muscle to the movable bone [Muscle contraction causes the insertion to move toward the origin; Movements occur along transverse, frontal, or sagittal planes]
simplest joint movements, occurs when one flat, or nearly flat, bone surface glides or slips over another (Intercarpal joints
Between articular processes of vertebrae)
increase or decrease the angle between two bones (flexion, extesnion, abduction, aduction, circumduction)
bending movement along sagittal plane, that decrease the angle of the joint, and brings articulating bones closer together
reverse of flexion and occurs at the same joints, invloves movement along the sagittal plane that increases angle between articulating bones, typically straight [Hyperextension - excessive extension beyond anatomical position]
movement of limb away from the midline or median plane of the body, along the frontal plane
opposite of abduction, movement of a limb toward the body midline, or midline of hand or foot.
turning of a bone around its own long axis. Medial and lateral rotation (Between C1 and C2 vertebrae
Rotation of humerus and femur)
turning backward, rotating forearm laterally so that the palm faces anteriorly or superiorly
Nonangular posterior movements in a transverse plane (ex: retracted jaw when brought back)
(Synovial) Hinge Joints
the cylindrical end of one bone conforms to a tough-shaped surface on another, motion is along a single plane and reselbles that of a mehanical hinge
(Synovial) Pivot Joints
the rounded end of one bone conforms to a "sleeve" or ring composed of bone (and possibly ligaments) of another, only movement allowed is uniaxial rotation of one bone around its own long axis
(Synovial) Condyloid Joints
(ellipsoidal joints) the oval articular surface of one bone fits into a complementary depression in another. Important characteristic is that both articulating surfaces are oval. Permits all angular motions
(Synovial) Saddle Joints
resemble condyloid joints, but they allow greater freedom of movement. Each articular surface has both concave and convex areas.
(Synovial) Ball-and-Socket Joints
the spherical or hemispherical head of one bone articulates with the cuplike socket of another. These joints are multiaxial and the most freely moviing synovial joints.
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