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The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 34 muscles in each hand, which can be categorised into groups including thenar, hypothenar, interossei, and lumbrical muscles. The fingers themselves do not contain muscles (other than arrector pili), but finger joints are moved by muscles in the forearm and palm. The long tendons that deliver motion from the forearm muscles can be observed moving under the skin at the wrist and on the back of the hand.
| Characteristics | Values |
|---|---|
| Number of muscles in each hand | 34 |
| Number of bones in each hand | 27 |
| Number of phalanges (finger bones) in each hand | 14 |
| Number of metacarpal bones in each hand | 5 |
| Number of carpal bones in each hand | 8 |
| Number of long flexors in each finger | 2 |
| Number of long flexors in the thumb | 1 |
| Number of short flexors in the thumb | 1 |
| Number of extensors in the thumb | 2 |
| Number of extensors in the index finger | 1 |
| Number of extensors in the little finger | 1 |
| Number of interossei muscles | 7 |
| Number of dorsal interossei muscles | 4 |
| Number of palmar interossei muscles | 3 |
| Number of lumbrical muscles | 4 |
| Number of muscles in the hypothenar muscle group | 3 |
| Number of muscles in the thenar muscle group | 3 |
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What You'll Learn
Finger muscles are controlled by the forearm
The human hand is a complex part of the body, comprising bones, muscles, nerves, connective tissue, and blood vessels. The fingers themselves do not contain muscles (other than arrector pili). Instead, the muscles that control finger movement are located in the palm and forearm. The long tendons that deliver motion from the forearm muscles can be observed moving under the skin at the wrist and on the back of the hand.
The muscles of the fingers can be subdivided into extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors, so-called because the muscle belly is located on the forearm. The fingers have two long flexors, located on the underside of the forearm, which attach to the phalanges of the fingers, allowing the fingers to bend. The thumb has one long flexor and a short flexor in the thenar muscle group, which enable grasping. The extensors are located on the back of the forearm and are connected to the dorsum of the fingers. The thumb has two extensors in the forearm, and the index finger and little finger have an extra extensor, used for pointing.
The thenar muscle group is found at the base of the thumb, forming the muscle bulk on that side of the hand. It is comprised of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The abductor pollicis brevis pulls the thumb away from the index finger, and the flexor pollicis brevis bends the thumb toward the little finger. The opponens pollicis enables the thumb to move away from the fingers, allowing us to grasp objects. The thenar eminence is made up of two groups of more powerful muscles in the hand itself, at the base of the thumb. The thenar muscles enable the thumb and the tips of the four fingers to touch each other (opposable thumb).
The hypothenar muscle group is formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. The hypothenar eminence muscles are used to control the movement of the little finger. They are mainly used for sticking out the little finger and pulling it inwards again and for tightening the skin that covers the hypothenar eminence. The hypothenar muscles line the outer edges of the palm on the outside of the little finger. They control the area of the hand that is opposite the thumb.
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There are 34 muscles in each hand
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 34 muscles in each hand, which work together to help us move our hands and fingers. These muscles are categorised into groups, including:
Thenar Muscles
These muscles control the thumb. They can be felt as a bulge at the base of the thumb in the palm of the hand. The thenar muscle group is made up of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The abductor pollicis brevis pulls the thumb away from the index finger, and the flexor pollicis brevis bends the thumb toward the little finger. The opponens pollicis is responsible for one of the most important functions of the human hand: the ability to bring the thumb away from the fingers, allowing us to grasp objects.
Hypothenar Muscles
These muscles line the outer edges of the palm on the outside of the little finger. They control the area of the hand that is opposite the thumb. The hypothenar muscle group is formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi.
Interossei Muscles
The interossei muscles are located between the metacarpal bones in the palm. There are four dorsal and three palmar interossei muscles. All interossei muscles bend the MCP joints, while the dorsal interossei allow us to spread our fingers away from each other. The palmar interossei pull our fingers together.
Lumbrical Muscles
The lumbricals are four thin, worm-like muscles that help bend the MCP joints and extend the fingers. They are located at the base of the four non-thumb fingers and help us flex our fingers.
The muscles of the fingers can be subdivided into extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors, which are called extrinsic because the muscle belly is located on the forearm. The fingers have two long flexors, located on the underside of the forearm, which attach to the phalanges of the fingers and allow for the bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group, which allow for grasping. The extensors are located on the back of the forearm and are connected to the dorsum of the fingers.
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Finger muscles are extrinsic or intrinsic
The muscles in the fingers can be categorised into two groups: extrinsic and intrinsic. The muscles that move the finger joints are in the palm and forearm. The long tendons that deliver motion to the forearm muscles can be seen moving under the skin at the wrist and on the back of the hand.
The extrinsic muscles are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. The fingers have two long flexors, located on the underside of the forearm. They insert by tendons 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. 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), which move 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 extensorhood mechanism.
The intrinsic muscle groups consist of smaller muscles solely located within the various hand osseofascial compartments within the anatomic confines of the wrist (proximally) and phalanges (distally). The intrinsics are important for various hand functions, such as pinch and grip strength. The thenar muscles are three short muscles located at the base of the thumb. The muscle bellies produce a bulge, known as the thenar eminence. They are responsible for the fine movements of the thumb. The median nerve innervates all the thenar muscles. The opponens pollicis is the largest of the thenar muscles, and lies underneath the other two. The hypothenar muscles form the hypothenar eminence, a muscular protrusion on the medial side of the palm, at the base of the little finger. These muscles are similar to the thenar muscles in both name and organisation. The ulnar nerve innervates the muscles of the hypothenar eminence.
The interossei muscles are located between the metacarpal bones of the hand. They can be divided into two groups: dorsal and palmar. In addition to their actions of abduction (dorsal interossei) and adduction (palmar interossei) of the fingers, the interossei also assist the lumbricals in flexion at the MCP joints and extension at the IP joints. There are four lumbricals in the hand, each associated with a finger. They are very crucial to finger movement, linking the extensor tendons to the flexor tendons. Denervation of these muscles is the basis for the ulnar claw and hand of benediction.
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The thumb has two extensors
The human thumb has nine skeletal muscles located in the hand and forearm, which allow for flexion, extension, adduction, abduction, and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: extrinsic hand muscles and intrinsic hand muscles. The extrinsic hand muscles have their muscle bellies located in the forearm, while the intrinsic hand muscles have their muscle bellies located in the hand.
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 of the extensors unite with the interosseous and lumbrical muscles to form the extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The index finger and the little finger also have an extra extensor, which is used for pointing.
The abductor muscles are responsible for moving the thumb away from the fingers. The abductor pollicis brevis originates on the scaphoid tubercle and the flexor retinaculum and inserts into the radial sesamoid bone and the proximal phalanx of the thumb. It is innervated by the median nerve. The abductor pollicis brevis pulls the thumb away from the index finger.
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The index and little fingers have an extra extensor
The muscles that move the finger joints are located in the palm and forearm. These muscles can be subdivided into extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors, so called because the muscle belly is located on the forearm. The fingers have two long flexors, located on the underside of the forearm, which allow for the bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group, which allow for grasping. 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 primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm, the tendons of which form the anatomical snuff box. The index finger and the little finger have an extra extensor, which is used for pointing. The extensors are situated within six separate compartments. The first four compartments are located in the grooves present 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.
The extensor that moves the index finger is called the extensor indicis. This muscle is not connected by the fibrous, oblique bands that pass between the tendons of the extensor digitorum, the muscle involved in the extension of fingers on the top of the hand. Consequently, the index and little fingers are able to move more freely than the other fingers. The extensor indicis extends the index finger by extending the metacarpophalangeal and proximal interphalangeal joints. It also aids in the upward flexion of the wrist and the adduction of the index finger. The extensor digitorum indicis is located within the fourth compartment.
The extensor that moves the little finger is called the extensor digiti minimi. The extensors of the index and little fingers are located within the fifth and sixth compartments, respectively.
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Frequently asked questions
The muscles in the fingers are called extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors. The intrinsic muscle groups are the thenar and hypothenar muscles, the dorsal and palmar interossei muscles, and the lumbrical muscles.
The functions of the finger muscles are flexion, extension, adduction, abduction, and circumduction. Flexion is the strongest movement, allowing the fingers to bend. The extensors straighten out the digits. The interossei muscles help spread the fingers away from each other and pull them back together. The thenar muscles enable the thumb and the tips of the four fingers to touch each other.
There are 34 muscles in each hand. There are two large muscles that produce flexion of each finger, and additional muscles that augment the movement. The thumb has one long flexor and a short flexor in the thenar muscle group.
The finger muscles are responsible for movement and dexterity. They work together with the bones, nerves, connective tissue, and blood vessels in the hand and wrist to allow humans to interact with their surroundings.
