GE 345: Week 8

Articulations

    Physiology/Kinesiology

• Week 1
• Week 2
• Week 3
• Week 4
• Week 5
• Week 6
• Week 7
• Week 8
• Week 9
• Project

[ Bone ] [ Skeleton ] [ Terms ]
[ Articulations ] [ Stability & Movement ]

Bones meet at the articulations, and with the exception of skull bones, these articulations are movable. T Structural classifications of bones include:

• Diarthrosis: from Greek, a joint in which there is a separation or articular cavity. The joint is encased in a ligamentous capsule lined with a synovial membrane that secretes synovial fluid. The articular surfaces are smooth and covered with cartilage, usually hyaline, occasionally fibrocartilage.
  • Irregular (arthrodial; plane): have irregularly shaped joint surfaces, flat or slightly curved. Movement permitted is of a gliding nature, as in the carpal joints.
  • Hinge (ginglymus): one spool-like surface, fits over a concave surface, gliding partially around it in a hinge type of mvoement, allowing flexion and extension, as elbows.
  • Pivot (trochoid; screw): characterized by a peglike pivot, or two long bones fitting oriented so one rolls around the other
  • Condyloid (ovoid; ellipsoidal): oval or egg-shaped convex surface fits into a concave surface. Biaxial joints, such as the wrist.
  • Saddle (sellar; reciprocal reception): modified condylar joint. Both ends of the convex surface are tipped up, making the surface concave in the other direction, like a western saddle. Meets with a reciprocally shaped surface. Greater movement than condyloid. ex: carpometacarpal joint of the thumb.
  • Ball-and-Socket (spehroidal; enarthrodial): spherical head of one bone fits into cavity of the other. Permits, flexion, extension, ab and adduction, circumduction, horizontal flexion and extension, and rotation. Triaxial. Shoulder, hip.
• Synarthrosis: from Greek "with joint." No separation or articular cavity. Two bones united by an intervening substance, continuous with joint surfaces, or a ligamentous connection between two bones. Has no articular cavity, hence no capsule, synovial membrane or fluid.
  • Cartilaginous (synchondrosis, Gr. "with cartilage"): Joints united by fibrocartilage permit bending or twising movements, such as between vertebrae. Joints united by hyaline cartilage permit only a slight compression, such as epiphyseal joints. Hyaline joints are eliminated in adults, but permanent between ribs and sternum.
  • Fibrous (suture, La "seam"): bone edges united by thin layer of fibrous tissue. No movement. Skull sutures.
  • Ligamentous (syndesmosis, Gr. "with ligament"): adjacent bodies tied together by one or more ligaments in the form of cords, bands or sheets. Limited movement of no specific type. ex: interosseus ligament at midunion of radius and ulna.

Movement at the articulations can be described by the following terms:

• Flexion: results in decreased angle between the two parts, typically in a front-back direction. Exception -- dorsiflexion.
• Extension: increases anggle between bones. Also in sagittal plane. Exception -- plantar flexion.
• Abduction: movement of a part away from midsagittal plane. Movement is in the frontal (coronal plane).
• Adduction: opposite of abduction. Movement toward midline of the body.
• Circumduction: movement involving all above movements.
• Rotation: bone turnes around an axis -- its own or another bone. Humerus rotates around its own axis, radius rotates around ulna, resulting in pronation and supination of the hand.

[ Bone ] [ Skeleton ] [ Terms ]
[ Articulations ] [ Stability & Movement ]