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The human hand is a complex structure, consisting of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, and many blood vessels and nerves. The muscles of the hand are skeletal muscles that enable the movement of the hand and fingers. Each finger has six muscles controlling its movement: three extrinsic and three intrinsic muscles. The index and little fingers have an extra extensor, used for pointing. The thumb has two extensors in the forearm. The intrinsic muscles are small muscles that originate in the wrist and hand and are responsible for fine motor movements of the fingers, such as writing or playing the piano. The extrinsic muscles originate in the forearm or elbow and control the movement of the wrist and hand. The interosseous muscles are a network of muscles found on and between the knuckles that enable the bending of the finger joints.
| Characteristics | Values |
|---|---|
| Number of muscles in the hand | 30 |
| Number of muscles controlling each finger | 6 |
| Number of extrinsic muscles controlling each finger | 3 |
| Number of intrinsic muscles controlling each finger | 3 |
| Number of interosseous muscles | 4 |
| Number of lumbrical muscles | 4 |
| Number of hypothenar muscles | 3 |
| Number of thenar muscles | 3 |
| Number of metacarpal bones | 5 |
| Number of phalanges in each finger | 3 |
| Number of phalanges in the thumb | 2 |
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What You'll Learn
- The human hand consists of 27 bones, 27 joints, 34 muscles, and many ligaments and tendons
- Each finger has six muscles controlling its movement: three extrinsic and three intrinsic
- The extrinsic muscles are attached to finger bones through long tendons that extend from the forearm through the wrist
- The intrinsic muscles are smaller muscles located within the hand itself and are responsible for fine motor movements of the fingers
- The index finger has an extra extensor, which is used for pointing
The human hand consists of 27 bones, 27 joints, 34 muscles, and many ligaments and tendons
The human hand is an intricate structure that enables us to perform various daily activities, such as driving, writing, and cooking. It consists of 27 bones, 27 joints, 34 muscles, numerous ligaments and tendons, and many blood vessels and nerves. The wrist, which is part of the hand, is made up of eight carpal bones that attach to the forearm's radius and ulna to form the wrist joint.
The 27 bones in the hand include 19 bones in the fingers and thumb, known as phalanges, and 5 metacarpal bones in the palm. Each finger has three phalanges, except for the thumb, which has two. These bones are connected by joints that allow for finger movement. The metacarpophalangeal joint (MCP) or knuckle joint connects the metacarpal bones to the phalanges. Each finger joint has collateral ligaments on either side, preventing abnormal sideways bending. The volar plate ligament is the strongest ligament in the hand, preventing hyperextension of the PIP joint.
The 34 muscles in the hand are divided into two groups: extrinsic and intrinsic. The extrinsic muscles, including the flexor digitorum superficialis and profundus, arise from the forearm and control finger movement. The intrinsic muscles, such as the thenar and hypothenar muscles, are smaller and located within the hand, contributing to grip strength and fine motor skills.
Tendons, like ropes, connect muscles to bones, enabling movement. For example, the flexor digitorum profundus tendon allows the bending of the index, middle, ring, and small fingers. Ligaments, on the other hand, are like thick rubber bands, connecting bones and stabilising joints. The carpal tunnel, a space in the wrist, allows nine tendons, four ligaments, and one nerve to pass through to the hand.
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Each finger has six muscles controlling its movement: three extrinsic and three intrinsic
The human hand is a complex structure, with 27 bones and 123 named ligaments. The muscles of the hand are the skeletal muscles responsible for its movement and that of the fingers. These muscles are divided into two groups: the extrinsic and intrinsic muscle groups. Each finger has six muscles controlling its movement: three extrinsic and three intrinsic.
The extrinsic muscle group is so-called because the muscle belly is located on the forearm. These muscles control crude movements and produce a forceful grip. The intrinsic muscles, on the other hand, are smaller muscles located within the hand itself. They are responsible for the fine motor functions of the hand, such as pinch and grip strength.
The extrinsic muscles are further divided into two subgroups: the long flexors and extensors. The flexors are located on the underside of the forearm, with tendons that attach to the phalanges of the fingers. The extensors are located on the back of the forearm and are connected to the dorsum 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 muscle, allowing the thumb to move in opposition and making grasping possible.
The intrinsic muscles are also divided into subgroups: the thenar, hypothenar, interossei, and lumbrical muscles. The thenar muscle group is located at the base of the thumb and is responsible for its fine movements. The hypothenar muscle group is found at the base of the little finger, with three muscles that allow the finger to pull away from the ring finger, bend at the MCP joint, and cup the hand. The interossei muscles are located between the metacarpal bones of the hand and assist in the abduction and adduction of the fingers. The lumbrical muscles are very important for finger movement, linking the extensor and flexor tendons.
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The extrinsic muscles are attached to finger bones through long tendons that extend from the forearm through the wrist
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, blood vessels, and parts of the lymphatic system. The wrist is the joint at the end of the forearm, acting as a hinge between the arm and hand. The hand includes the palm, fingers, and thumb, and the wrist acts as a pivot point, allowing the hand to move, flex, and rotate.
The muscles of the hand are subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscles are called so because the muscle belly is located on the forearm. These muscles flex and extend the digits of the hand. The intrinsic muscles, on the other hand, are smaller muscles located within the hand itself. They are responsible for various hand functions, such as pinch and grip strength.
The extrinsic muscles are attached to the finger bones through long tendons that extend from the forearm through the wrist. These tendons are like strong, flexible ropes, connecting the muscles to the bones. The forearm muscles are divided into two compartments: the anterior flexor compartment and the posterior extensor compartment. The muscles in these compartments work together to move the elbow, forearm, wrist, and digits of the hand.
The flexor digitorum superficialis (FDS) is an example of an extrinsic muscle. It arises from the medial epicondyle (an elbow bone) and has four independent muscle bellies, from which four tendons arise. These tendons cross the wrist, pass through the carpal tunnel, and spread out to the index, middle, ring, and small fingers. The primary function of the FDS is to bend the middle joint of each finger, except the thumb. The independence of each finger's FDS contributes to the hand's dexterity and skill in performing tasks requiring fine motor control, such as using chopsticks.
Another example of an extrinsic muscle is the brachioradialis (BR), which originates from outside the elbow and inserts into the end of the radius bone, just below the wrist joint. The BR helps flex the elbow and can twist the forearm to reposition the thumb. The extensor pollicis longus is an extrinsic muscle that attaches to the thumb, allowing it to be straightened and used for gestures like a "thumbs up" or "hitchhiker" sign.
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The intrinsic muscles are smaller muscles located within the hand itself and are responsible for fine motor movements of the fingers
The muscles in the human body are groups of cells that have the ability to contract and relax. These muscles are broadly divided into two types: skeletal muscles and autonomic muscles. The skeletal muscles are further divided into two groups: extrinsic and intrinsic muscles. The extrinsic muscles are the long flexors and extensors, and they are called so because the muscle belly is located on the forearm. The intrinsic muscles, on the other hand, are smaller muscles located within the hand itself. These muscles are responsible for various hand functions, such as pinch and grip strength, and fine motor movements of the fingers.
The intrinsic muscles are crucial for the movement of the hand and fingers. These muscles are subdivided into four groups: the thenar, hypothenar, interossei, and lumbrical muscles. The thenar muscles are three short muscles located at the base of the thumb, which is also known as the thenar eminence. These muscles are responsible for the fine movements of the thumb. The hypothenar muscles, on the other hand, are located at the base of the little finger, forming a muscular protrusion known as the hypothenar eminence. The interossei muscles are located between the metacarpal bones of the hand, with four dorsal and three palmar interossei muscles. The lumbrical muscles are very important for finger movement, as they link the extensor tendons to the flexor tendons. There are four lumbricals in the hand, each associated with a finger.
The intrinsic muscles of the hand are innervated by the radial, median, and ulnar nerves from the brachial plexus. The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, and the first and second lumbricals. The radial nerve innervates the finger extensors and the thumb abductor, which are the muscles that extend at the wrist and metacarpophalangeal joints. The ulnar nerve innervates the remaining intrinsic muscles of the hand, including the hypothenar muscles.
The understanding of the intrinsic hand muscle groups is of utmost importance as denervation and loss of function may lead to significant deficits in hand function. For instance, Klumpke palsy, or total hand claw, is a condition that results in the loss of all intrinsic hand muscles, leading to palmar atrophy and weakness in thumb and little finger abduction, flexion, and opposition. Therefore, a comprehensive analysis of hand function should include an assessment of the strength, coordination, and speed of hand movements, along with a thorough physical examination.
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The index finger has an extra extensor, which is used for pointing
The human hand is made up of skeletal muscles that are responsible for its movement and the movement of the fingers. These muscles are divided into two groups: extrinsic and intrinsic. The extrinsic group is made up of long flexors and extensors, while the intrinsic group is made up of smaller muscles located within the hand itself. The extensors are responsible for straightening out the digits.
The index finger has its own extensor, known as the extensor indicis, which allows it to extend independently from the other fingers. This muscle is narrow and elongated and is found in the posterior compartment of the forearm. It is one of the deep extensors of the forearm, along with the supinator, abductor pollicis longus, extensor pollicis longus, and extensor pollicis brevis muscles. The extensor indicis attaches to the extensor expansion over the MCP joint of the index finger (at the knuckle). It is this independence from other extensor tendons that allows us to point with our index finger.
The extensor indicis arises from the distal third of the dorsal part of the body of ulna and from the interosseous membrane. It runs through the fourth tendon compartment together with the extensor digitorum, from where it projects into the dorsal aponeurosis of the index finger. Opposite the head of the second metacarpal bone, it joins the ulnar side of the tendon of the extensor digitorum, which belongs to the index finger. The extensor indicis tendon lies in the fourth dorsal (extensor) compartment of the wrist, deep to the extensor retinaculum.
The index finger is one of the few fingers with its own separate extensor muscle, enabling it to extend independently. This independence is what allows us to point with our index finger. The other fingers, except for the little finger, do not have this same level of independence in their movement. The little finger also has an extra extensor, which is why it can also be moved independently.
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Frequently asked questions
Technically, there are no muscles in the fingers, except for the adductor pollicis and abductor pollicis longus at the base of the thumb. The muscles that enable finger movement are located in the forearm and wrist.
The extrinsic muscles are located in the forearm and control finger movement. These include the flexor digitorum profundus, flexor digitorum superficialis, and flexor carpi ulnaris muscles.
The intrinsic muscles are smaller muscles located in the wrist and hand that enable fine motor movements of the fingers. These include the thenar, hypothenar, interossei, and lumbrical muscles.
