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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 are categorised into groups such as thenar muscles, hypothenar muscles, interossei muscles, and lumbrical muscles. These muscles work together to help you move your fingers. However, interestingly, there are no muscles in your fingers. All the muscles that control finger motion are located in the hand and forearm. The fingers have two long flexors, located on the underside of the forearm, which allow for the actual bending of the fingers.
| Characteristics | Values |
|---|---|
| Number of muscles in each hand | 34 |
| Types of muscles | Thenar, Hypothenar, Interossei, Lumbrical, Flexor, Extensor |
| Parts of the hand | Phalanges, Metacarpals, Carpals |
| Function of muscles | Contract and relax, allowing movement of the bones in the hand |
| Location of muscles | Forearm, wrist, palm, hand |
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What You'll Learn
The hand contains 34 muscles
The human hand is a complex network of bones, muscles, nerves, connective tissue, blood vessels, and ligaments. There are 34 muscles in each hand, which work together with the wrist to help us interact with the world around us. The muscles in the forearm initiate hand movements, and only the tendons of these muscles are found in the hand. The tendons are connected to the muscles and bones, allowing for movement.
The muscles in the hand can be categorised into four groups: thenar, hypothenar, interossei, and lumbrical muscles. The thenar muscles are located at the base of the thumb, forming the muscle bulk on the thumb side of the hand. They are comprised of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. 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.
The hypothenar muscles are formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. These muscles line the outer edges of the palm on the outside of the pinky finger and control the area of the hand that is opposite the thumb. The interossei muscles are located between the metacarpal bones in the palm and help the fingers move side-to-side. There are four dorsal and three palmar interossei muscles. The dorsal interossei allow us to spread our fingers away from each other, while the palmar interossei pull our fingers together.
The lumbrical muscles are at the base of the four non-thumb fingers and help us flex our fingers. The main role of these muscles is to allow the fingers to straighten, although they can also help bend the MCP joints, which are at the knuckle. The adductor pollicis is another muscle that allows us to pinch. It helps fill the first web space between the thumb and index finger.
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Finger muscles are in the palm and forearm
The human hand is a complex network of bones, muscles, nerves, connective tissue, blood vessels, and ligaments. There are 34 muscles in each hand, which can be categorised into groups. The muscles that move the finger joints are in the palm and forearm.
The forearm contains the flexors and extensors, which are extrinsic muscles. The fingers have two long flexors, located on the underside of the forearm, which attach to the phalanges of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. 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, while the index finger and little finger have an extra extensor, which is used for pointing.
The thenar muscle group is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. It 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 allows the thumb to move away from the fingers, enabling us to grasp objects.
The hypothenar muscle group is formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. 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.
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There are two types of finger muscles: extrinsic and intrinsic
The muscles that move the finger joints are in the palm and forearm. While fingers do not contain muscles (other than arrector pili), the muscles of the fingers can be subdivided into two groups: extrinsic and intrinsic.
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), 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 extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used, for instance, for pointing.
The intrinsic muscle groups consist of smaller muscles located within the various hand osseofascial compartments within the anatomic confines of the wrist (proximally) and phalanges (distally). They are responsible for the fine motor functions of the hand. The intrinsic muscle groups are the thenar and hypothenar muscles (thenar referring to the thumb, hypothenar to the small finger), the dorsal and palmar interossei muscles (between the metacarpal bones) and the lumbrical muscles. 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 opponens digit minimi lies deep to the other hypothenar muscles. The interossei muscles begin between the bones of the hand. 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 first dorsal interosseous muscle is the largest and originates from the 1st and 2nd hand bones. It forms the contour between the thumb and index finger when looking at the top of the hand and is often the first muscle to shrink in patients with severe cubital tunnel syndrome due to damage of the ulnar nerve. In addition to pulling the index finger away from the middle finger, it also pulls the thumb towards the index finger. This action provides strength and stability when pinching.
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The thumb has two extensors in the forearm
The muscles that move the finger joints are located in the palm and forearm. The forearm is the section of the upper limb that extends from the elbow to the wrist. The forearm muscles are divided into two compartments: the anterior flexor compartment and the posterior extensor compartment. These compartments contain twenty muscles that act on the elbow and wrist joints, as well as the carpometacarpal, metacarpophalangeal, and interphalangeal joints of the hand.
The extensors are located on the back of the forearm and are connected to the dorsum of the fingers. They 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 thumb also 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, forming the muscle bulk on the thumb side of the hand.
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The thenar muscle group is found at the base of the thumb
The abductor pollicis brevis is the most superficial muscle of the group, meaning it is the closest to the surface of the skin. This muscle plays a crucial role in abducting the thumb, or moving it away from the index finger. It also assists in flexing and opposing the thumb, enabling movements such as pinching and grasping. The abductor pollicis brevis receives its blood supply primarily from the superficial palmar branch of the radial artery and is innervated by the recurrent branch of the median nerve.
The flexor pollicis brevis is another important muscle within the thenar group. It is responsible for flexing the thumb, allowing it to bend toward the small finger. This movement is crucial for making a fist or gripping objects securely. The flexor pollicis brevis has two heads, or points of origin, that differ in their innervation. The superficial head is innervated by the recurrent branch of the median nerve, while the deep head receives input from the deep branch of the ulnar nerve.
The opponens pollicis is the largest of the thenar muscles and lies underneath the other two. It performs a vital function in the human hand: the ability to bring the thumb away from the fingers, allowing us to grasp objects effectively. The opponens pollicis originates from the tubercle of the trapezium and the associated flexor retinaculum, inserting onto the lateral margin of the first metacarpal bone. It is innervated by the median nerve, specifically its recurrent branch.
While not officially part of the thenar muscle group, the adductor pollicis is often discussed alongside these muscles due to its role in thumb movement. This short and broad muscle arises from two muscular heads and is responsible for producing strong adduction, or movement towards the body, of the thumb at the first carpometacarpal joint. The adductor pollicis is innervated by the deep branch of the ulnar nerve and receives its blood supply from the deep palmar arch.
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Frequently asked questions
The fingers do not contain any muscles. The muscles that control finger movement are located in the forearm and hand.
The extensors are located on the back of the forearm and are connected to the dorsum of the fingers. The flexors are located on the underside of the forearm.
The muscles in the hand that control the fingers include the thenar muscles, hypothenar muscles, interossei muscles, and lumbrical muscles.
The primary function of the extensors in the forearm is to straighten the fingers. The flexors in the forearm allow for the bending of the fingers.
The thenar muscles control the thumb, while the hypothenar muscles control the area of the hand opposite the thumb. The interossei muscles help the fingers move side-to-side, and the lumbrical muscles help flex the fingers.
