Example: The frontal bone. (The frontal bone of the skull is actually a bony fusion of
two bones. Approximately 10 percent of the time, this fusion fails to take place; the
original suture between the bones remains and is called a metopic suture.)
c. Cartilagenous Joints. These are also nonmovable joints.
(1) Synchondrosis. A cartilagenous joint in which the bones are held
together by hyaline cartilage.
SYN = together
CHONDRO = cartilage
Example: Epiphyseal plate.
(2) Symphysis. A cartilagenous joint in which the bones are held together by
a disc of fibrocartilage.
Example: Pubic symphysis.
d. Synovial Joints. In the synovial type of joints, the bones move on one
another so as to allow various motions of the body parts. The "ovial" part of the name
refers to the fact that the fluid substance seen in this type of joint appeared to the old
anatomists to be like raw egg white (ovum = egg).
4-9. A "TYPICAL" SYNOVIAL JOINT
A "typical" synovial joint is one which has parts common to all of the synovial
joints. In a sense, it is imaginary. It is not actually a specific synovial joint. It is a
composite. It is illustrated in figure 4-2. The "typical" synovial joint has the following
a. Bones. Bones are the levers of motion. They are the site of attachment for
b. Articular Cartilages. The "contact" points of the bones are usually covered
with a layer of lubricated cartilage. Where these cartilages end, the synovial
membranes begin. Cartilages provide a smooth surface to reduce friction.