Hand Anatomy and Function PDF

**Functions** Positioning the hand Unlike the lower limb, which is used for support, stability, and locomotion, the upper limb is highly mobile for positioning the hand in space. The shoulder is suspended from the trunk predominantly by muscles and can therefore be moved relative to the body. Sli...

**Functions** Positioning the hand Unlike the lower limb, which is used for support, stability, and locomotion, the upper limb is highly mobile for positioning the hand in space. The shoulder is suspended from the trunk predominantly by muscles and can therefore be moved relative to the body. Sliding (protraction and retraction) and rotating the scapula on the thoracic wall changes the position of the **glenohumeral joint** (**shoulder joint**) and extends the reach of the hand ( [Fig. 7.3](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0020) ). The glenohumeral joint allows the arm to move around three axes with a wide range of motion. Movements of the arm at this joint are flexion, extension, abduction, adduction, medial rotation (internal rotation), lateral rotation (external rotation), and circumduction ( [Fig. 7.4](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0025) ). Fig. 7.3 Movements of the Scapula. (**A**) Rotation. (**B**) Protraction and retraction.  Fig. 7.4 Movements of the Arm at the Glenohumeral Joint. The major movements at the **elbow joint** are flexion and extension of the forearm ( [Fig. 7.5A](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0030) ). At the other end of the forearm, the distal end of the lateral bone, the radius, can be flipped over the adjacent head of the medial bone, the ulna. Because the hand is articulated with the radius, it can be efficiently moved from a palm-anterior position to a palm-posterior position simply by crossing the distal end of the radius over the ulna ( [Fig. 7.5B](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0030) ). This movement, termed pronation, occurs solely in the forearm. Supination returns the hand to the anatomical position. Afbeelding met joint, skelet Automatisch gegenereerde beschrijving Fig. 7.5 Movements of the Forearm. (**A**) Flexion and extension at the elbow joint. (**B**) Pronation and supination. At the **wrist joint** , the hand can be abducted, adducted, flexed, extended, and circumducted ( [Fig. 7.6](https://www-clinicalkey-com.utrechtuniversity.idm.oclc.org/f0035) ). These movements, combined with those of the shoulder, arm, and forearm, enable the hand to be placed in a wide range of positions relative to the body. Fig. 7.6 Movements of the Hand at the Wrist Joint. **The hand as a mechanical tool** One of the major functions of the hand is to grip and manipulate objects. Gripping objects generally involves flexing the fingers against the thumb. Depending on the type of grip, muscles in the hand act to: - modify the actions of long tendons that emerge from the forearm and insert into the digits of the hand, and - produce combinations of joint movements within each digit that cannot be generated by the long flexor and extensor tendons alone coming from the forearm. **The hand as a sensory tool** The hand is used to discriminate between objects on the basis of touch. The pads on the palmar aspect of the fingers contain a high density of somatic sensory receptors. Also, the sensory cortex of the brain devoted to interpreting information from the hand, particularly from the thumb, is disproportionately large relative to that for many other regions of skin.