Final answer:
The dorsum of the hand is involved in extending the fingers and hand, while muscles in this area assist in movements essential for daily function such as opposition of the thumb for grasping objects. Circumduction adds the capability of circular motion in several joints.
Step-by-step explanation:
Function of Dorsum (Back) and Fingers of Hand
The dorsum (back) of the hand includes muscles such as the extensor digitorum which extends the phalanges, and the extensor carpi radialis brevis which extends and abducts the hand at the wrist. These muscles, along with others like the dorsal interossei, facilitate movements such as the extension of fingers, and the abduction and flexion of the middle fingers at the metacarpophalangeal joints. Additionally, the action of the opposition movement of the thumb toward the fingers of the same hand is essential for grasping and holding objects, making it a fundamental human function for numerous daily activities. The ability to move the hand from a palm backward position to a palm forward position (supination) and vice versa (pronation) is also critical for hand function and dexterity.
The dorsal region also comprises the erector spinae group which is the primary extensor of the vertebral column, helping in maintaining posture and enabling bending backwards. The galea aponeurosis connects the frontalis and occipitalis muscles, contributing to facial expressions and head movements.
Meanwhile, movements like circumduction involve a combination of flexion, abduction, extension, and adduction, allowing for a circular motion of the arm, thigh, hand, thumb, or fingers.