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The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. Despite this, fingers do not contain muscles. The muscles that move the finger joints are in the palm and forearm. Tendons connect muscles to bones, and the tendons that help in the movement of fingers are attached to 17 muscles in the palm and 18 muscles in the forearm. The two major actions of fingers – flexing and extending – are carried out by flexor and extensor muscles, respectively.
| Characteristics | Values |
|---|---|
| Are there muscles in the fingers? | No |
| Muscles that move the fingers | Located in the palm and forearm |
| Number of muscles in the palm | 17 |
| Number of muscles in the forearm | 18 |
| Tendons | Connect muscles to bones |
| Ligaments | Connect bones to other bones |
| Extensors | Help to straighten fingers |
| Flexors | Help to bend fingers |
| Radial nerve | Activates finger extensors and muscles in the wrist |
| Median nerve | Connects to many branches of smaller nerves that spread out into the hand and wrist |
| Ulnar nerve | Moves muscles of the hypothenar eminence and muscles between the metacarpal bones |
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What You'll Learn
Fingers do not have muscles
Fingers do not contain muscles, apart from the arrector pili muscle (APM) which is attached to the hair follicles and makes the hair stand erect when contracted. The muscles that move the finger joints are located in the palm and forearm. The muscles in the forearm end as tendons in the hand, which transmit movement to the tendons in the hand and help us move our fingers. Tendons are fibrous connective tissues that act as a bridge between muscles and bones, allowing movement to occur.
The hand and wrist are a complex network of bones, muscles, nerves, connective tissue, and blood vessels. The hand is supplied with blood through two main arteries, which curve around in an arch shape in the palm. Each finger is supplied by four bundles of nerves and blood vessels. The muscles and skin of the hand are supplied by three nerves: the radial nerve, the median nerve, and the ulnar nerve.
The muscles of the hand can be divided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors, called extrinsic because the muscle belly is located on the forearm. The intrinsic group are the smaller muscles located within the hand itself. The intrinsic muscle groups are the thenar (thumb) and hypothenar (little finger) muscles; the interossei muscles (four dorsally and three volarly) originating between the metacarpal bones; and the lumbrical muscles arising from the deep flexor to insert on the dorsal extensor hood mechanism. The fingers have two long flexors, located on the underside of the forearm, which insert by tendons into the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible.
The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensor hood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm, and the index finger and little finger have an extra extensor, used for pointing. The extensors are situated within six separate compartments. The first four compartments are located in the grooves on the dorsum of the inferior side of the radius, while the fifth compartment is between the radius and ulna. The sixth compartment is in the groove on the dorsum of the inferior side of the ulna.
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Muscles in the forearm and palm control finger movement
The muscles in the forearm and palm are essential for finger movement and overall hand function. The forearm, situated between the elbow and the wrist, contains around 20 muscles that act on the elbow and wrist joints, as well as the carpometacarpal, metacarpophalangeal, and interphalangeal joints of the hand. These muscles are divided into two compartments: the anterior flexor compartment and the posterior extensor compartment.
The anterior flexor compartment, or the flexors, is responsible for bending the wrist and fingers. This group includes muscles such as the flexor carpi radialis, which primarily bends the wrist and moves it towards the thumb, and the flexor digitorum superficialis, which bends the middle joint of each finger except the thumb. The flexor digitorum profundus is another important muscle in this compartment, allowing for the bending of the index, middle, ring, and small fingers.
The posterior extensor compartment, or the extensors, is located on the back of the forearm and is responsible for straightening the digits. The thumb has two extensors, while the index finger and little finger have an extra extensor for pointing. The extensors are connected to the interosseous and lumbrical muscles, forming the extensor hood mechanism.
In addition to the forearm muscles, the intrinsic muscle groups within the hand itself also play a crucial role in finger movement. These include the thenar muscles of the thumb, the hypothenar muscles of the little finger, and the interossei and lumbrical muscles. The interossei muscles allow us to spread our fingers apart or pull them together, while the lumbrical muscles help straighten the fingers and bend the MCP joints. The adductor pollicis, another intrinsic muscle, is responsible for providing power for pinching between the thumb and index finger.
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Tendons in the hand help move the fingers
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. Tendons are fibrous cords made of collagen, with blood vessels and cells to maintain tendon health and repair injured tendons. They are attached to muscles and bones, and they help move the fingers by delivering motion from the forearm muscles.
The muscles that move the finger joints are in the palm and forearm. Tendons in the hand help move the fingers by transmitting motion from the forearm muscles. The long tendons extend from the forearm muscles, through the wrist, and into the hand, where they attach to the phalanges of the fingers. These tendons work together with the muscles in the forearm to produce movement in the fingers.
The fingers have two long flexors located on the underside of the forearm, which insert by tendons into the phalanges of the fingers. The deep flexor attaches to the distal phalanx, while the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group, which also contains the opponens and abductor brevis muscles. These muscles enable the thumb to move in opposition to the other fingers, making grasping possible.
The extensors are located on the back of the forearm and are connected to the dorsum of the fingers. They work with the interosseous and lumbrical muscles to form the extensor hood mechanism. The primary function of the extensors is to straighten the digits. The thumb has two extensors in the forearm, while the index finger and little finger have an extra extensor each, used for pointing, for instance.
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Intrinsic and extrinsic muscles of the hand
The muscles of the hand are skeletal muscles that facilitate hand and finger movement. They can be divided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscles are the long flexors and extensors, so called because the muscle belly is located in the forearm. The intrinsic muscles, on the other hand, are smaller muscles located within the hand itself and are responsible for fine motor functions.
The intrinsic muscle groups include the thenar (thumb) and hypothenar (little finger) muscles. The thenar muscles consist of one long flexor and one short flexor, which allow the thumb to move in opposition, making grasping possible. The opponens and abductor brevis muscles are also part of the thenar group. The hypothenar muscles, meanwhile, form a muscular protrusion on the medial side of the palm, at the base of the little finger. The abductor digiti minimi is the most superficial muscle in this group, abducting the little finger. The flexor digiti minimi brevis, which flexes the metacarpophalangeal joint of the little finger, lies laterally to the abductor digiti minimi.
The intrinsic muscle groups also include the interossei muscles, which originate between the metacarpal bones. There are four dorsal and three palmar interossei muscles. While all interossei bend the MCP joints, the dorsal interossei allow us to spread our fingers apart, and the palmar interossei pull our fingers together. The first dorsal interosseous muscle is the largest and forms the contour between the thumb and index finger. The lumbrical muscles, which arise from the deep flexor, are also part of the intrinsic group. They allow the fingers to straighten and help bend the MCP joints. The adductor pollicis, which fills the space between the thumb and index finger, is also an intrinsic muscle.
The extrinsic muscles, meanwhile, include the extensors, which are located on the back of the forearm and are connected to the dorsum of the fingers. The primary function of the extensors is to straighten the digits. The thumb has two extensors in the forearm, and the index finger and little finger have an extra extensor each. The flexors, which are also part of the extrinsic group, are located on the underside of the forearm and are connected to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers.
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Interossei muscles allow fingers to spread and pull together
The human hand is a complex structure with various muscles, bones, and joints working together to allow for movement and dexterity. While fingers themselves do not contain muscles, the muscles that move the finger joints are located in the palm and forearm. These muscles, along with their tendons, are responsible for the movement and flexibility of the fingers.
The interossei muscles are intrinsic muscles of the hand, located between the metacarpal bones. There are four dorsal and three palmar interossei muscles. The dorsal interossei muscles allow the fingers to spread away from each other, while the palmar interossei pull the fingers together. This movement is known as abduction and adduction, respectively.
The dorsal interossei muscles are short muscles that attach to the adjacent sides of the metacarpals, which are the bones in the hand that connect to the fingers. They are responsible for abducting the second, third, and fourth digits, or fingers, at the metacarpophalangeal (MCP) joints. MCP joints, also known as knuckles, are the joints closest to the fingers. The dorsal interossei also assist in flexion, or bending, of these fingers at the MCP joints and contribute to extension at the interphalangeal (IP) joints, which are the joints within the fingers.
The palmar interossei muscles, on the other hand, act antagonistically to the dorsal interossei. They bring the fingers towards the midline, or towards each other. The palmar interossei are unipennate muscles, originating from the metacarpals of the respective digits they are associated with. They adduct the first, second, fourth, and fifth digits about a long axis through the third digit.
Together, the dorsal and palmar interossei muscles play a crucial role in finger movement, allowing for both abduction and adduction, as well as contributing to flexion and extension at the MCP and IP joints.
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Frequently asked questions
No, fingers do not have muscles, except for the arrector pili muscle (APM) which is attached to the hair follicles. The muscles that move the finger joints are in the palm and forearm.
The muscles in the forearm end as tendons in the hand. These tendons transmit the movement initiated by the muscles to the fingers.
The extrinsic muscles arise from the elbow and forearm and connect to the fingers as tendons. The intrinsic muscles originate within the hand and insert into the fingers, providing intrinsic support for coordination and fine movements.
The intrinsic muscle groups are the thenar (thumb) and hypothenar (little finger) muscles, the interossei muscles, and the lumbrical muscles.
The extensor digiti minimi, the extensor indicis proprius, the supinator, and the biceps are some examples of extrinsic muscles.
