Dominic Stone
The human hand is a complex structure, with more than 30 individual muscles in the hand and forearm working together to achieve a diverse range of movements. The fingers have two long flexors, located on the underside of the forearm, which attach 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 hand also contains interossei muscles, which help fingers move side-to-side, and lumbrical muscles, which help to straighten the fingers.
| Characteristics | Values |
|---|---|
| Number of bones in the hand | 27 |
| Number of muscles in the hand and forearm | 30+ |
| Primary function of extensors | To straighten out the digits |
| Number of extensors in the thumb | 2 |
| Number of extensors in the index finger and little finger | 1 each |
| Function of the thenar muscles | Enable the thumb and the tips of the four fingers to touch each other |
| Function of the hypothenar eminence muscles | Control the movement of the little finger |
| Function of the lumbricals | Help bend the metacarpophalangeal joints and extend the fingers |
| Function of the opponens pollicis | Bring the thumb away from the fingers to grasp objects |
| Function of the adductor pollicis | Provide power for pinching |
| Function of the flexor digitorum profundus | Bend the index, middle, ring, and small fingers |
| Function of the flexor digitorum superficialis | Flex and curl fingers |
| Function of the extensor pollicis brevis | Extend the thumb |
| Function of the extensor pollicis longus | Extend the thumb |
| Function of the extensor indicis | Extend the index finger |
| Function of the extensor digitorum | Extend the middle and ring fingers |
| Function of the extensor digiti minimi | Extend the little finger |
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What You'll Learn
The muscles that straighten fingers
The muscles that control the movement of the fingers are located in the forearm and hand. The muscles that straighten the fingers are called the extensors, and they are located on the back of the forearm. When these muscles contract, they pull on the bones of the fingers and wrist, leading to an extension movement. This action allows you to straighten your fingers and raise your wrist, which is important for many everyday tasks such as typing, pointing, opening a book, or lifting an object from a table.
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. The tendons of the extensors in the forearm form the anatomical snuff box. The index finger and little finger have an extra extensor, which is used for pointing.
The lumbricals are another group of muscles that help to straighten the fingers, although they also help to bend the MCP joints, which are at the knuckle. The name of this muscle is derived from the Greek word for earthworm. The adductor pollicis is another muscle that fills the first web space between the thumb and index finger and provides power for pinching.
The interossei muscles also play a role in finger movement. 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 away from each other, and the palmar interossei pull our fingers together.
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The muscles that bend fingers
The muscles that control the bending of the fingers are primarily the flexors. The fingers have two long flexors, located on the underside of the forearm. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. These 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 thenar muscle group is found at the base of the thumb and is made up of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The flexor pollicis brevis bends the thumb toward the small finger, while the flexor pollicis longus allows us to bend the tip of our thumb.
The index, middle, ring, and small fingers are bent by the flexor digitorum profundus. This muscle is located deep in the forearm and gives rise to four tendons that pass through the carpal tunnel and insert into the tips of these fingers. Due to its insertion past the last joint of these fingers, it can bend all three finger joints. However, the middle, ring, and small fingers share a common muscle belly, which usually prevents us from bending the tip of one of these fingers without the others bending as well. The index finger has a separate muscle belly, allowing for independent movement.
The lumbricals of the hand are four thin, worm-like muscles that help bend the metacarpophalangeal (MCP) joints, which are at the knuckle. The main role of the lumbricals is to allow the fingers to straighten, but they can also help with bending the MCP joints. The dorsal interossei muscles also bend the MCP joints and allow us to spread our fingers away from each other. In contrast, the palmar interossei muscles pull our fingers together.
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The muscles that control finger movement side-to-side
The human hand is composed of numerous bones, muscles, ligaments, tendons, sheaths, arteries, veins, and nerves. The muscles are the structures that contract, allowing movement of the bones in the hand. Tendons connect muscles to bones and enable movement.
The interossei muscles are between the metacarpal bones in the palm. They help the fingers move side-to-side. 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 away from each other. The palmar interossei pull our fingers together.
The lumbrical muscles are at the base of the four non-thumb fingers. They help us flex our fingers and straighten them. The hypothenar muscles line the outer edges of the palm on the outside of the pinkie finger. They control the area of the hand opposite the thumb.
The hand and wrist are complex parts of the body that allow us to touch and control objects. The ligaments in the hand are fibrous tissues that help bind together the joints in the hand. The sheaths are tubular structures that surround part of the fingers.
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The muscles that control the thumb
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles 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 in the hand.
The thenar eminence refers to the group of muscles on the palm at the base of the thumb. The three muscles composing the thenar eminence are the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. The abductor pollicis brevis pulls the thumb away from the index finger, while the flexor pollicis brevis bends the thumb toward the small finger. The opponens pollicis is responsible for pulling the thumb away from the fingers, allowing us to grasp objects.
The other two muscles that influence thumb movement are the adductor pollicis and the first dorsal interosseous muscle. The adductor pollicis is used to pull the thumb towards the palm and has the primary role of providing power for pinching. The first dorsal interosseous muscle is the largest muscle in the hand, forming the contour between the thumb and index finger.
The thumb has one long flexor and a short flexor in the thenar muscle group. The thumb also has other muscles in the thenar group, such as the opponens and abductor brevis muscle, which move the thumb in opposition, enabling grasping. The flexor pollicis longus, a ventral forearm muscle, allows us to bend the tip of our thumb.
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The muscles that control the little finger
The human hand is a complex structure that allows for a great range of movement and precision. 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 and the index finger work like tweezers, allowing the hand to grip very small objects in a controlled way.
The hypothenar eminence muscles are made up of three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. These muscles form the bulk of the small finger side of the hand. The abductor digiti minimi is the most superficial of the three muscles and allows the little finger to pull away from the ring finger. The flexor digiti minimi allows the little finger to bend at the MCP joint, and the opponens digiti minimi allows us to cup our hands, bringing the little finger towards the thumb.
The interossei muscles also play a role in controlling the little finger, as they allow us to spread our fingers away from each other and pull them together. The first dorsal interosseous muscle is the largest and originates from the first and second hand bones. It forms the contour between the thumb and index finger when viewed from the top of the hand.
Additionally, the lumbricals are crucial to finger movement, including the little finger. They link the extensor tendons to the flexor tendons, allowing for flexion at the MCP joint and extension at the interphalangeal (IP) joints. The medial two lumbricals, which include the lumbrical of the little finger, are innervated by the ulnar nerve.
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Frequently asked questions
The muscles that control finger movement include the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. The flexor digitorum superficialis and flexor digitorum profundus extend from the forearm and insert into the phalanges of the fingers, allowing them to bend. The flexor pollicis longus is responsible for flexing the thumb. The interossei muscles, located between the metacarpal bones, enable fingers to move side-by-side. The lumbrical muscles, located at the base of the four non-thumb fingers, also assist in finger flexion.
Finger extension is facilitated by extensor muscles located on the back of the forearm. These include the extensor pollicis brevis (thumb), extensor pollicis longus (thumb), extensor indicis (index finger), extensor digitorum (middle and ring fingers), and extensor digiti minimi (little finger).
The thenar and hypothenar muscles are responsible for controlling the movement of the thumb and little finger, respectively. The thenar muscles, located at the base of the thumb, enable the thumb to touch the fingertips, allowing for a precision grip. The hypothenar muscles, found on the outer edge of the palm near the little finger, facilitate the movement of the little finger, such as sticking it out or pulling it inwards.
