Download Classes of Joints

Classes of Joints
Fibrous Joints
In fibrous joints bones are interconnected by
fibrous tissue; there is no joint cavity. The bones
are capable of little or no movement. Joints in
this group are classified further on the basis of
structure as sutures, syndesmoses, or gomphoses.
Sutures which are limited to the skull are of three
different types:
a. Serrate sutures form distinct wavy lines. The
adjoining bones firmly interlock with each other along
their serrated margins.
b. Lap(squamous) sutures occur where two bones have
overlapping beveled edges.
c. Plane (butt) sutures occur where bones have
straight, nonoverlapping edges.
Gomphoses
Gomphoses are specialized joints consisting of pegs that fit into sockets that are held in
place by fine bundles of collagen fibers called periodental ligaments. The joints between
the teeth and
the sockets (alveoli) of the mandible and maxillae
Syndesmosis (Right Radioulnar)
Syndesmoses are a type of fibrous joint in which the bones are farther apart than those in a suture and are
joined by ligaments. (An example is shown on the left between the radius and the ulna.) Syndesmoses are the
most movable of fibrous joints
Cartilaginous Joints
Cartilaginous joints unite two bones by means of either hyaline cartilage or fibrocartilage.
If the bones are joined by hyaline cartilage, they are called synchondroses (for example, the
attachment of a rib to the sternum); if they are joined by fibrocartilage, they are
Synostoses (Bony Joints)
Synostoses are formed when various fibrous and cartilaginous joints ossify with age. Two distinct bones fuse together thus the bones appear as
one. For example, the mandible is represented at birth by right and left bones; in early childhood, these bones become fused.
Synovial Joints
Synovial joints allow considerable movement. They consist of the following:
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Articular cartilage on the ends of bones, which provides a smooth surface for articulation.
A meniscus is a pad of fibrocartilage that may occur between the articulating bones. It absorbs and provides support.
A joint capsule of fibrous connective tissue, which holds the bones together while permitting flexibility, and a synovial membrane,
which produces synovial fluid that lubricates the joint. Bursae are fibrous sacs filled with synovial fluid that act like cushion pads and
protect skin, tendons, or bone from structures that could rub against them.z
Skeletal muscle action produces movements at synovial joints. Typically, one end of a muscle, the origin, is attached to a relatively immovable or
fixed part on one side of a joint, and the other end of the muscle, the insertion, is fastened to a movable part on the other side
Flexion is movement that bends a joint so that the angle between the parts decreases and come closer together.
Extension is movement that straightens a joint so that the angle between the parts increases and move farther apart.
Hyperextension is movement that increases the angle of a joint beyond 180°. The parts are extended beyond the normal range of motion.
Rotation is turning a structure around its long axis.
Circumduction is movement in which one end of an appendage remains relatively stationary while the other end makes a circular motion.
Elevation moves a structure superiorly.
Depression moves a structure inferiorly.
Protraction is moving a structure in an anterior direction.
Retraction is moving a structure back to the anatomic position.
Dorsiflexion is a movement in which the toes are raised.
Plantar flexion is hyperextension of the foot so that the toes point downward.