Joints • A joint is the site of meeting of two or more bones. • Joints are classified into three types (depending on the material that hold the articular bones together):
Fibrous joints • Sutures: only seen in between the skull bones and they frequently ossify with age). • Syndesmosis: • Inferior tibiofibular joint (no movement in this joints and never ossify). • Interosseous membrane connecting bones of forearm & leg. • Gomphosis:in the joints between the teeth and jaws. Each tooth is connected to the socket by periodontal membrane.
Cartilaginous joints • Primary cartilaginous: these are temporary joints, in which the bones are connected by hyaline cartilage that ossifies with age. No movement is possible. This type is seen in: • Epiphyseal plate connecting epiphysis and metaphysis. • 1st sternocostal joint between 1st costal cartilage and sternum.
Cartilaginous joints • Secondary cartilaginous: the bones are connected by disc of fibrocartilage, which rarely ossifies with age. A small amount of movement is possible. These joints are seen in the joints of midline of body: • Intervertebral discs • Symphysis pubis • Manubriosternal junction
Synovial joints • are held together by fibrous capsule & characterized by presence of joint cavity. Synovial joints are freely movable and represent most joints of the body. • The capsule is lined by synovial membrane that secretes lubricating fluid (synovial fluid) for the articular surfaces. • Articular ends are covered by hyaline cartilage. • The capsule is thickened in certain parts to form ligaments, which provide strength and flexibility to the joint.
Synovial Joints • Allow considerable movement • Most joints that unite bones of axial and peripheral skeleton • Articular cartilage and disks • Joint cavity and capsule • Synovial membrane and fluid • Bursae
Types of Movement • Angular • Flexion and Extension • Abduction and Adduction • Circular • Rotation • Circumduction Flexion and Extension
Special Movements • Unique to only one or two joints • Types • Elevation and Depression • Protraction and Retraction
Points to Remember • A joint or articulation is a meeting between two bones and does not necessarily imply movement • A joint can be classified according to its structure • Synovial joints are the most complex • Specific terms are used to describe the movements of joints that are freely movable. • Commonly grouped in opposing pairs that move a part of the body in relation to the anatomical position.