Wrist, Hand, and Foot LO 2
2. Describe the arrangement of compartments and muscles in the hand. Differentiate between extrinsic and intrinsic hand muscles.
The hand is the most distal and the manual part of the upper limb; with the wrist at the junction of the forearm and hand. The digits are numbered 1 to 5 with the thumb (lateral side) as digit 1 and the little finger (medial side) as digit 5. The palmar surface has a central concavity separating two eminences: lateral, the thenar eminence, is larger; medial, the hypothenar eminence, is smaller.
The fascia of the hand is continuous with the antebrachial fascia. The fascia is thin over the thenar and hypothenar eminences, but much thicker over the central compartment. The fascia over the central portion of the palm forms the palmar aponeurosis. If the palmaris longus muscle is present, it inserts into the palmar aponeurosis.
The palmar portion of the hand is divided into 5 compartments: thenar, hypothenar, central, and the deep adductor and interosseous compartments.
- Thenar compartment: the most lateral compartment of the hand on the palmar side. This compartment is at the base of the thumb.
- Deep adductor and interosseous compartments: contains the muscles of the palm of the hand deep to the central compartment. Tendons are the large adductor pollicis and the interosseous muscles. The adductor pollicis adducts the thumb, the palmar interossei adduct the digits toward midline – the middle (digit 3) finger, and the dorsal interossei abduct the digits away from the midline.