Answers, BIO 2310, Articulations


1. Synarthrosis is not moveable, Amphiarthrosis is slightly moveable, Diarthrosis is freely moveable. The structure is discussed below and includes fibrous, cartilaginous and synovial.

2. Fibrous joints are bone-fibrous connective tissue-bone. No joint cavity. Examples are suture of skull (synarthrosis); syndesmosis such as tibia/fibula distally (amphiarthrosis) and gomphosis which is tooth and alveolus of jaw (synarthrosis). A cartilaginous joint has bone-cartilage-bone with no joint cavity. An example is a symphysis at the pubic symphysis or intervertebral disc where the cartilage is fibrocartilage (amphiarthrosis). Another cartilaginous joint is a synchondrosis found between ribs and sternum or the epiphyseal growth plates.

3. The key difference in the diarthrotic synovial joint is that there is a joint cavity. The cavity is filled with synovial fluid made by the synovial membrane. There is an outer fibrous joint capsule as well as ligaments holding the bones in place.

4. Flexion – decreasing the angle of articulating bones. Flexion of knees is bending of the knees, flexion of shoulder joint is when you swing your arm forward, flexion of the hip is when you swing your thigh forward. Extension is increasing the angle of the articulating bones. Extension of knee is straightening it, extension of shoulder/hip is swinging arm/thigh backwards. Hyperextension is extension past anatomical position. Abduction/adduction is movement away/toward midline. Rotation is turning, lateral rotation would be turning your arm/leg outward, and medial rotation is turning arm/leg inward. Circumduction is circles such as head circles. Inversion/eversion is turning soles toward/away from each other. Dorsiflexion is flexion of ankle joint as with pointing your toes toward the ceiling. Plantar flexion is actually extension of ankle joint such as standing on tip toes. Protraction/ retraction is a movement forward/backward on a plane parallel with the floor. Supination/ pronation is palms forward/backward. Elevation/depression is a movement up/down.

5. Gliding is flat against flat, vertebral facets is an example with movement side to side and back and forth. Pivot is a point in a ring with the C1-C2 being an example allowing turning (rotation) of head left/right. Hinge is a spool in a corresponding concave surface such as trochlea of humerus in trochlear notch of ulna. It allows flexion and extension. Condyloid = Ellipsoid joint is an egg in a spoon shape. It is the most common shape with an example being the second metacarpus-proximal phalanx joint. This joint allows flexion, extension, lousy circumduction, adduction and abduction. Saddle joint is a modified ellipsoidal joint allowing more free movement. An example is the metacarpophalangeal joint for your thumb. All of the same movements as the ellipsoidal joint but better movements. A ball in socket joint is typified by the coxofemoral joint which allows nearly every movement.