Physiology/Kinesiology
|
[ 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 ]
|