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The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, blood vessels, and parts of the lymphatic system. There are 34 muscles in each hand, which work together to help you move your hand and fingers. These muscles are soft tissue made of stretchy fibres and are categorised into intrinsic and extrinsic muscles. Intrinsic muscles are located within the hand itself and are responsible for fine motor functions. Extrinsic muscles are found near the outside of the hand and in the forearm. They work together with intrinsic muscles to give the hand its strength and dexterity.
| Characteristics | Values |
|---|---|
| Number of muscles in each hand | 34 |
| Types of muscles | Intrinsic, extrinsic, skeletal, autonomic, somatic, voluntary, flexor, extensor, thenar, hypothenar, interossei, lumbrical, abductor pollicis longus, adductor pollicis, palmaris longus, palmaris brevis, rotator cuff, subscapularis, latissimus dorsi, flexor carpi radialis, pronator teres, flexor digitorum profundus, extensor digitorum profundus |
| Functions of muscles | Strength, dexterity, movement, flexion, extension, adduction, abduction, opposition, pinching, grasping, straightening, pulling, rotation, stabilisation |
| Parts of the hand | Bones, muscles, nerves, connective tissue, blood vessels, tendons, ligaments, lymphatic system |
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What You'll Learn
- The hand and wrist are a complex network of muscles, nerves, tendons, ligaments, and blood vessels
- Intrinsic muscles are located within the hand and are responsible for fine motor functions
- Interossei muscles allow us to spread or pull our fingers together
- Lumbrical muscles allow the fingers to straighten and assist in bending the MCP joints
- The palmaris longus muscle travels down the forearm to the wrist and palm, where it functions as a flexor
The hand and wrist are a complex network of muscles, nerves, tendons, ligaments, and blood vessels
The intrinsic muscles inside the hand work with the extrinsic muscles near the outside of the hand and forearm to give the hand its strength and dexterity. The intrinsic muscles of the hand include the adductor pollicis, which provides power for pinching. The lumbrical muscles allow the fingers to straighten and help bend the MCP joints. The interossei muscles are located between the metacarpal bones of the hand and can be divided into two groups: dorsal and palmar. The dorsal interossei allow us to spread our fingers away from each other, while the palmar interossei pull our fingers together.
The hand has two long flexors located on the underside of the forearm, which attach by tendons to the phalanges of the fingers, allowing for the bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group, which, along with the opponens and abductor brevis muscle, allow the thumb to move in opposition, 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 extensorhood mechanism, and their primary function is to straighten the digits.
The hand and wrist have two groups of tendons: extensor tendons, which help extend and straighten the fingers, hand, and wrist; and flexor tendons, which help flex and curl the fingers, hand, and wrist.
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Intrinsic muscles are located within the hand and are responsible for fine motor functions
The human hand is a complex structure, with various muscles and tendons working together to enable movement and dexterity. Intrinsic muscles are those located within the hand itself, and they are responsible for the fine motor functions of the hand. These muscles are distinct from the extrinsic muscles, which are found in the forearm and produce crude movements and a forceful grip.
Intrinsic hand muscles include the thenar muscles, which are three short muscles located at the base of the thumb. These muscles produce a bulge known as the thenar eminence and are responsible for the thumb's fine movements. The opponens pollicis is the largest of the thenar muscles and lies beneath the other two. The thenar muscles are innervated by the median nerve.
The hypothenar muscles, on the other hand, are located at the base of the little finger and form the hypothenar eminence, a muscular protrusion on the medial side of the palm. The hypothenar muscles are similar in name and organisation to the thenar muscles. The abductor digiti minimi is the most superficial muscle in this group, and it abducts the little finger. The flexor digiti minimi brevis, meanwhile, flexes the metacarpophalangeal joint of the little finger. The hypothenar muscles are innervated by the ulnar nerve.
The interossei muscles are another group of intrinsic muscles that begin between the bones of the hand. There are four dorsal and three palmar interossei muscles. While all interossei muscles 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 are crucial to finger movement, linking the extensor tendons to the flexor tendons. There are four lumbricals in the hand, each associated with a finger. The lateral two lumbricals, associated with the index and middle fingers, are innervated by the median nerve, while the medial two lumbricals, associated with the little and ring fingers, are innervated by the ulnar nerve. The primary role of the lumbricals is to allow the fingers to straighten, although they also assist in bending the MCP joints.
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Interossei muscles allow us to spread or pull our fingers together
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, blood vessels, and parts of the lymphatic system. The hand and wrist have two groups of tendons: extensor tendons and flexor tendons. Extensor tendons help extend and straighten the fingers, hand, and wrist, while flexor tendons help flex and curl the fingers, hand, and wrist.
The interossei muscles are intrinsic muscles of the hand located between the metacarpal bones in the palm. 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. 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 looking at the top of the hand.
The interossei muscles receive innervation from the deep ulnar branch of the ulnar nerve. Therefore, any injury to the ulnar nerve may have debilitating implications on specific intrinsic hand muscle functions, including finger abduction and adduction, which are primarily controlled by the interossei muscles. Ulnar nerve entrapment has been determined to be the second most common presenting compression neuropathy in patients. Depending on which nerve fibers are compromised, patients may have weakness in abduction or adduction of the fingers.
The lumbrical muscles are the primary contributors to flexion at the metacarpophalangeal joints as well as extension at the DIP and PIP joints. The interossei also play a minor role in these movements. The lumbricals are located at the base of the four non-thumb fingers and help us flex our fingers. The index finger and the little finger have an extra extensor, used, for instance, 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.
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Lumbrical muscles allow the fingers to straighten and assist in bending the MCP joints
The human hand has several muscles that enable its complex movement. The lumbrical muscles are four small, worm-like muscles on each hand, named after the Greek word for earthworm. They are deep muscles that originate from tendons and insert into the extensor expansions, instead of attaching to the bone. This makes their attachment points quite mobile, allowing them to perform two different actions: flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal joints. The MCP joints are at the knuckle, and the lumbrical muscles allow the fingers to straighten at these joints.
The lumbrical muscles are numbered 1-4 from the most radial/lateral to the most ulnar/medial. Each lumbrical muscle originates from one or two adjacent tendons of the flexor digitorum profundus muscle. Lumbricals 1 and 2 are usually unipennate, with their fibres arising obliquely from one tendon, while lumbricals 3 and 4 are bipennate, arising from two adjacent tendons. The first lumbrical arises from the radial side and palmar surface of the tendon of the index finger. The third lumbrical arises from the ulnar side of the middle finger tendon and the radial side of the ring finger tendon. The fourth lumbrical arises from the ulnar side of the ring finger tendon and the radial side of the little finger tendon.
The lumbrical muscles play an important role in the complex movement of the hand, such as holding a pen, and contribute to the hand's overall dexterity. They also contain many muscle spindles and have a large fibre length, indicating that they likely play a significant role in proprioception and sensory feedback, which is crucial for precision pinching and other intricate hand movements.
In addition to the lumbrical muscles, the interossei muscles also bend the MCP joints. There are four dorsal and three palmar interossei muscles. While the dorsal interossei allow us to spread our fingers apart, the palmar interossei pull our fingers together.
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The palmaris longus muscle travels down the forearm to the wrist and palm, where it functions as a flexor
The human hand is a complex structure, with several muscles working together to enable its function. The palmaris longus muscle is one such muscle, located in the anterior forearm. It is a long, thin muscle that extends from the distal humerus to the root of the hand, ending at the wrist and palm. This muscle is unique in that it is absent in 10-25% of people, with a higher prevalence of absence in women than men.
The palmaris longus muscle is part of the superficial layer of muscles in the anterior forearm, which also includes the pronator teres, flexor carpi ulnaris, flexor carpi radialis, and flexor digitorum superficialis muscles. These muscles work together to flex the wrist and fingers. The palmaris longus muscle specifically functions as a flexor of the wrist, aiding in wrist flexion and tensioning the palmar aponeurosis, a fibrous tissue layer between the thenar and hypothenar muscles. This tension helps to maintain the hand's grip while holding objects.
The palmaris longus tendon has clinical significance, particularly for surgeons. Its long and slender structure makes it suitable for use as a tendon graft in various procedures, such as opponensplasty and radial palsy. Additionally, the tendon can be used to put the muscle in a state of tension, making it visible and palpable for diagnostic purposes.
The palmaris longus muscle is innervated by the median nerve, which passes between the tendons of the palmaris longus and flexor carpi radialis muscles. The blood supply to the palmaris longus muscle comes from a branch of the anterior ulnar recurrent artery, a branch of the ulnar artery. The median artery may also contribute to the blood supply if it is well developed.
In summary, the palmaris longus muscle plays an important role in wrist flexion and grip strength, working in conjunction with other muscles in the anterior forearm. Its tendon has clinical applications, and its function is facilitated by innervation from the median nerve and blood supply from the ulnar artery.
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Frequently asked questions
Yes, the hands have muscles. There are 34 muscles in each hand.
The muscles in the hand can be categorized into intrinsic and extrinsic muscles. The intrinsic muscles are located within the hand itself and are responsible for fine motor functions. The extrinsic muscles are located near the outside of the hand and in the forearm.
The intrinsic and extrinsic muscles work together to give the hand its strength and dexterity.
The intrinsic muscles include the thenar muscles, hypothenar muscles, and lumbrical muscles. The thenar muscles control the thumb, the hypothenar muscles line the outer edges of the palm, and the lumbrical muscles allow the fingers to straighten.
The radial nerve system innervates the finger extensors and the thumb abductor, the median nerve system innervates the flexors of the wrist and digits, and the ulnar nerve system innervates the remaining intrinsic muscles of the hand.
