Hands and fingers are important appendages for humans for a wide variety of tasks: cooking, playing musical instruments and writing are a few common activities which utilize the hands and fingers. The anatomy of the opposable thumb gives humans and other primates motor skills and abilities that most other organisms don’t have. Finally, the fingers are one of the most important body parts for sending sensory information about our surroundings to the brain. This article will discuss the basic anatomy and nerves of the fingers and hand in order to understand and appreciate these complex and unique parts of the body.
Anatomy of the hand and fingers
Like other appendages, the hand and fingers get their structure and shape from several bones and muscles which are held together by tendons and ligaments. A complex network of blood vessels and nerves are also found in the hand, and the whole thing is covered by the integument (skin).
The bones of the hands and fingers are more or less homologous to those found in the feet. Beginning from the bones of the forearm, the radius and ulna, we have the bones of the wrist which are collectively known as the “carpals”: hamate, pisiform, triquetrum, lunate, trapezium, trapezoid, scaphoid and capitate. Then come the five bones of the palm and back of the hand, known as the “metacarpals” which will continue on to form the fingers or “phalanges”. Each finger is made up of three phalanges bones (proximal, medial and distal) except for the thumb, which only has two (just like the big toe in the case of the feet).
Muscles of the hand
As you might expect, the hand contains many small muscles which give it the ability to carry out tasks that require fine and controlled movements, and special muscles for the opposable thumb which makes many daily tasks possible. There are several abductor and adductor muscles which allow the fingers to spread apart and come back together. Running between the metacarpal bones are 3 palmar interosseous muscles (palm of hand between index and middle, middle and ring, and ring and pinky fingers) and 4 dorsal interosseous muscles (back of hand between thumb and index, index and middle, middle and ring, ring and pinky fingers). Special muscles of the thumb include the adductor pollicis, flexor pollicis brevis, abductor pollicis brevis and opponens pollicis. Special muscles for the fifth finger (pinky) include the abductor digiti minimi and flexor digiti minimi brevis.
The fingers themselves primarily contain tendons which attach the muscles of the hand to the phalanges, allowing the fingers to flex and extend at each joint.
Nerves of the hand and fingers
The hands and fingers have one of the largest densities of both motor and sensory nerves in the human body. Sensory nerves are especially abundant at the fingertips, and these nerves receive information from external stimuli (such as temperature, pain, or pressure) and send this information to the brain in the form of electrical impulses (synapses). In turn, the brain sends impulses back to the muscles of the hands via motor nerves (or motor neurons) which cause the muscles to move.
The nerves of the hands and fingers originate in the spinal nerves of the C8 and T1 vertebrae. Each nerve is comprised of a single neuron cell which extends from the spinal cord through the arms all the way to the hands and fingers. The major nerves in the hand and fingers are the ulnar nerve (which innervates the fourth and fifth fingers), a branch of the radial nerve (innervates the dorsal thumb, index, middle and ring fingers) and the median nerve (innervates the.