Joints

Joints Are places of union between two or more bones. Are innervated as follows: The nerve supplying a joint also supplies the muscles that move the joint and the skin covering the insertion of such muscles. Are classified on the basis of their structural features into fibrous, cartilaginous and synovial types. Fibrous joints (synarthroses) Are joined by fibrous tissue, have no joint cavities , and permit little movement. 1. Sutures Are connected by fibrous connective tissue (i.e., like uniting a wound with stitches). Are found between the flat bones of the skull. 2. Syndesmoses Are connected by fibrous connective tissue. Occur as the inferior tibiofibular and tympanostapedial syndesmoses. Cartilaginous joints Are united by cartilage and have no joint cavity. 1. Primary cartilaginous joints (synchondroses) Are united by hyaline cartilage. Permit no movement but growth in the length of the bone. Include epiphyseal cartilage plates (the union between the epiphysis and the diaphysis of a growing bone) and spheno-occipital and manubriosternal synchondroses. 2. Secondary cartilaginous joints (symphyses) Are joined by fibrocartilage and are slightly movable joints. Include the pubic symphysis and the intervertebral disks. Synovial (diarthrodial) joints Permit a great degree of free movement and are classified according to the shape of the articulation and/or type of movement. Are characterized by four features: joint cavity, articular (hyaline) cartilage,synovial membrane (which produces synovial fluid), and articular capsule. 1. Plane (gliding) joints Are united by two flat articular surfaces and allow a simple gliding or sliding of one bone over the other. Occur in the proximal tibiofibular, intertarsal, intercarpal, intermetacarpal,carpometacarpal, sternoclavicular, and acromioclavicular joints. 2. Hinge (ginglymus) joints Resemble door hinges and allow only flexion and extension. Occur in the elbow, ankle, and interphalangeal joints. 3. Pivot (trochoid) joints Are formed by a central bony pivot turning within a bony ring. Allow only rotation (movement around a single longitudinal axis). Occur in the superior and inferior radioulnar joints and in the atlantoaxial joint. 4. Condylar (ellipsoidal) joints Have two convex condyles articulating with two concave condyles. The shape of the articulation is ellipsoidal. Allow flexion and extension and occur in the wrist (radiocarpal),metacarpophalangeal, knee (tibiofemoral), and atlanto-occipital joints. 5. Saddle (sellar) joints Resemble a saddle on a horse's back and allow flexion and extension, abduction and adduction, and circumduction but no axial rotation. Occur in the carpometacarpal joint of the thumb and between the femur and patella. 6. Ball-and-socket (spheroidal) joints Are formed by the reception of a globular (ball-like) head into a cup-shaped cavity and allow movement in many directions. Allow flexion and extension, abduction and adduction, medial and lateral rotations, and circumduction and occur in the shoulder and hip joints. ◄.....Go back to the Gross Anatomy homepage