The hands are one of our most physically active body parts. They help us accomplish different tasks, like the gross and fine motor skills. Hand dominance is in the control of the opposite hemisphere of the brain. The hand is also rich in sensory receptors; thus, making it very sensitive to tactile stimulation. To understand how a person is able to manipulate the hands, you need to study the different hand muscles responsible for the movements.
Extrinsic Hand Muscles
The extrinsic hand muscles are in the forearm, but the tendons extend to the hands. They acquired the name extrinsic because the muscle belly is outside the hand. Whenever you move your hands, fibrous connective tissue, known as the retinaculum, covers the flexor and extensor tendons to keep them in place while accomplishing the movement. Without the retinaculum, it is impossible to coordinate the movements in your hands.
Major Extrinsic Muscles
To start a motion, the major extrinsic muscles must coordinate the movement. The anterior muscles, flexi carpi ulnaris and the flexi carpi radialis flex the wrist, whereas the three posterior muscles, the extensor carpi radialis, extensor carpi radialis brevis and extensor carpi ulnaris extend the wrist. You can move your wrist sideward, forward and backward because of these groups of muscles.
Movement of the Fingers
The fingers move because of the flexor digitorum superficialis, flexor digitorum profundus and extensor digitorum. Your pinky has an additional muscle, the extensor digiti minimi, and the index finger has the extensor indicis. If you notice, your thumb has greater range of motion compared to the other fingers. This is due to the presence of the abductor policis longus, extensor pollicis longus and the extensor pollicis brevis. With your thumb, you can easily grasp a large object or pick a small needle.
Intrinsic Hand Muscles
The intrinsic muscles keep their name because the entire muscles are in the hands. If you want to move your entire hand nearer the body, you can accomplish this action by simply making use of your interossei dorsales and the adductor digiti minimi. If you want to do the opposite, the muscle interossei palmares will allow you to do it.
The small muscle groups in the hands make all your motions possible. Although at birth, humans need to develop good hand and brain coordination; in due time, you will master all the gross and fine motor skills and appreciate how these little muscles work together to help you manipulate the things around you.