JOINT MOVEMENTS

2. 3. SLIGHTLY MOVABLE. In these joints the bones are held together by broad flat- tened disks of cartilage and ligaments (e.g., vertebrae and symphysis pubis). FREELY MOVABLE. Such joints include the knee, hip, and shoulder. These joints are further subdivided into (figs. 3-23A and 3-23B): HINGE JOINTS . . . . . . . . . .elbow, finger, and knee BALL-AND-SOCKET JOINTS . . . . shoulder and hip JOINT MOVEMENTS Joint movements are generally divided into four types: GLIDING is the simplest type of motion. It is one surface moving over another without any rotary or angular motion. This motion exists be- tween two contiguous or adjacent surfaces. Figure 3-23A.—Hinge joint. Figure 3-23B.—Ball-and-socket joint. ANGULAR motion decreases or increases the angle between two adjoining bones. The more common types of angular motion are: Flexion—bending the arm or leg. Extension—straightening or unbending, as in straightening the forearm, leg, or fingers. Abduction—moving an extremity away from the body. Adduction—bringing an extremity toward the body. ROTATION is a movement in which the bone moves around a central point without being displaced, such as turning the head from side to side. CIRCUMDUCTION is movement of the hips and shoulders. Other types of movement generally used to in- dicate specific anatomical positions include the following: SUPINATION is turning upward, as in plac- ing the palm of the hand up. PRONATION is turning downward, as in placing the palm of the hand down. EVERSION is turning outward, as in turning the sole of the foot to the outside. INVERSION is turning inward, as in turning the sole of the foot inward. MUSCLES Muscles make up about one-half of the total body weight. Their main functions are threefold: Providing movement, including internal functions such as peristalsis in the intestines. Maintaining body posture through muscle tone, as in the muscles of the head, neck and shoulders, which keep the head up. Providing heat through chemical changes that take place during muscle activity, such as mild exercise that warms the body on cold days. addition, muscles are involved in such essential bodily functions as respiration, blood 3-14