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The muscles that control finger motion are located in the hand and forearm. There are two long flexors to each finger: the flexor digitorum profundus (FDP) and the flexor digitorum superficialis. The FDP is the main gripping muscle and is supplied by two different nerves. The flexor carpi radialis is another muscle that bends the wrist and moves it towards the thumb. The thumb has its own set of muscles, including the flexor pollicis longus and flexor pollicis brevis, which flex and extend the thumb, respectively. The palmar and dorsal interossei control the abduction and adduction of the fingers, allowing them to spread apart and squeeze together.
| Characteristics | Values |
|---|---|
| Muscles that control finger motion | Located in the hand and forearm |
| Number of muscles involved in finger flexion | 2 |
| Names of the 2 muscles | Flexor digitorum profundus, Flexor digitorum superficialis |
| Muscles involved in finger extension | Extensor digitorum communialis |
| Muscles that control finger abduction and adduction | Palmar and dorsal interossei |
| Muscles that control thumb flexion | Flexor pollicis longus, Flexor pollicis brevis |
| Muscles that control thumb extension | Extensor pollicis longus, Extensor pollicis brevis |
| Muscles that control thumb abduction | Abductor pollicis longus, Abductor pollicis brevis |
| Muscles that move the thumb out towards the small finger | Opponens muscles |
| Muscle that contributes to the pinching grip of the thumb | Adductor pollicis |
| Muscle that controls the proximal phalanx's flexion | Lumbricals |
| Muscle that controls the interossei | Dorsal interossei |
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What You'll Learn
The flexor digitorum profundus (FDP) is the main gripping muscle
The FDP is the chief gripping muscle and acts best when the wrist is extended. It is the sole flexor of the distal interphalangeal (DIP) joint of the second to fifth digits. The FDP also acts as a flexor of the midcarpal (wrist), metacarpophalangeal, and proximal interphalangeal (PIP) joints of the index, middle, ring, and little fingers. The FDP works in conjunction with the flexor digitorum superficialis, which attaches to the middle phalanx.
The FDP is supplied by the anterior interosseous artery, a branch of the common interosseous artery. It is innervated by the anterior interosseous nerve, a motor branch of the median nerve, and the ulnar nerve. The FDP lymphatic drainage is part of the upper limb lymph system, consisting of superficial and deep lymphatic vessels.
Injuries to the FDP can result in conditions such as Quadrigia and Jersey finger. Quadrigia occurs when the FDP tendons to the 5th, 4th, and 3rd fingers are interconnected with the separate tendon to the index finger, resulting in a weak grasp and an inability to make a full fist. Jersey finger is a rupture of the FDP tendon from its distal attachment, leading to a loss of active flexion at the distal interphalangeal joint.
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The thumb has its own set of muscles
Interestingly, the thumb has its own set of muscles, which allow the human hand to perform unique functions. The thumb has two flexors, two extensors, and two abductors. These muscles are the flexor pollicis longus, flexor pollicis brevis, extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus, and abductor pollicis brevis. The thumb also has its own adductor, the adductor pollicis, which allows for a pinching grip.
The flexor pollicis longus is a long flexor that originates near the elbow and runs through the forearm. It is one of the muscles that control finger flexion, along with the flexor digitorum profundus and flexor digitorum superficialis. Finger flexion occurs when you make a fist, and it is the strongest movement that the fingers can perform. It is used during grasp and pinch actions.
The flexor digitorum profundus is a muscle in the forearm that flexes the fingers. It is an extrinsic hand muscle, as it acts on the hand while its muscle belly is located in the forearm. The muscle gets its name from the Latin 'deep bender of the fingers'. It originates in the upper 3/4 of the anterior and medial surfaces of the ulna, interosseous membrane, and deep fascia of the forearm. The muscle has four tendons, one for each of the second to fifth fingers, which attach to the palmar base of the distal phalanx.
The flexor digitorum superficialis is also a flexor muscle that attaches to the middle phalanx. It is a multi-tendoned extrinsic flexor that flexes the proximal interphalangeal joints of the four fingers. The muscle comprises four digital components, each with a tendon that inserts into its corresponding finger.
The lumbricals are the only muscles in the body that do not attach to bone. They control the flexion of the proximal phalanx and originate from the flexor digitorum profundus, attaching to the extensor hood.
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The lumbricals control the proximal phalanx's flexion
The human hand is a complex structure that serves as the origin and insertion point for a vast number of muscles. The intrinsic muscles of the hand enable fine motor movements, while the extrinsic muscles provide strength. The lumbricals are a set of four intrinsic hand muscles that play a crucial role in finger flexion and extension.
The lumbrical muscles, named for their resemblance to earthworms, originate from the flexor digitorum profundus (FDP) tendons and insert onto the extensor expansions of the fingers. Each finger, except the thumb, is connected to two lumbricals. These muscles have a unique architecture, with muscle fibres extending up to 90% of their length, enabling high contraction velocity and long excursion.
The primary function of the lumbricals is not to directly flex or extend the fingers but to act as a tensioning mechanism within the flexor and extensor system. When the FDP contracts, it pulls on the lumbrical, and the finger extends. This mechanism helps stabilise the digital position, similar to a guy line on a tower. The lumbricals also provide sensory feedback to the interphalangeal and metacarpophalangeal joints of the fingers.
While the lumbricals are not the primary workhorses of digital extension, they do play a role in finger flexion, specifically at the metacarpophalangeal (MCP) joints. Studies have shown that electrical stimulation of the lumbrical muscle results in MCP joint flexion. Additionally, the lumbricals help control the fine and delicate movements of the fingers, coordinating with other hand muscles. This coordination is essential for precision grip, dexterous hand movements, and tasks like gripping objects and typing.
In summary, the lumbricals' control of the proximal phalanx flexion is part of their broader function in the hand's intricate muscle system. By working in tandem with other muscles and providing sensory feedback, the lumbricals enable the hand to perform a wide range of tasks with precision and dexterity.
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The hypothenar muscle group
The hypothenar muscles form a fleshy prominence on the medial side of the palm, known as the hypothenar eminence. They are similar in name and organisation to the thenar muscles, which are also located in the palm. The hypothenar eminence is innervated by the ulnar nerve, which supplies the three hypothenar muscles. Lesions of the ulnar nerve can result in "hypothenar atrophy." The blood supply for the hypothenar eminence comes primarily from the ulnar artery via the superficial palmar arch.
The function of the hypothenar muscles is to enable a variety of movements of the little finger, including flexion, abduction, lateral rotation, and opposition. The abductor digiti minimi, for example, originates from the palmar surface of the pisiform bone and the dorsal aponeurosis, and it inserts into the ulnar aspect of the base of the proximal phalanx of the little finger. This muscle is innervated by the deep branch of the ulnar nerve.
The palmaris brevis, despite being innervated by a different branch of the ulnar nerve, also contributes to grip strength by tightening the palmar aponeurosis. It achieves this by originating from the palmar aponeurosis and flexor retinaculum and attaching to the dermis of the skin on the medial margin of the hand. This muscle is small and thin, and its function is to wrinkle the skin of the hypothenar eminence and deepen the curvature of the hand.
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The flexor carpi radialis helps move the wrist towards the thumb
The muscles that control finger motion are located in the hand and forearm. There are no muscles in the fingers. Each finger has two muscles involved in flexion: the flexor digitorum profundus, which attaches to the distal phalanx, and the flexor digitorum superficialis, which attaches to the middle phalanx.
The flexor carpi radialis is a muscle in the forearm that acts to flex and abduct the hand. The name 'flexor carpi radialis' is derived from three Latin words: 'flexor' meaning 'to bend', 'carpi' meaning 'wrist', and 'radialis' referring to the muscle's location on the radial side of the forearm. It is one of four muscles in the superficial layer of the anterior compartment of the forearm. The flexor carpi radialis originates from the medial epicondyle of the humerus as part of the common flexor tendon and runs just laterally to the flexor digitorum superficialis. It inserts on the anterior aspect of the base of the second metacarpal and has small slips to both the third metacarpal and trapezium tuberosity. The flexor carpi radialis is a relatively thin muscle located on the anterior part of the forearm. It is a superficial muscle that becomes very visible as the wrist comes into flexion.
The flexor carpi radialis is the closest visible tendon to the thumb when the wrist is in a fully flexed position. It is involved in flexion and abduction. The main function of the flexor carpi radialis is to provide flexion of the wrist and assist in the abduction of the hand and wrist. The muscle also acts as a dynamic scaphoid stabiliser.
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Frequently asked questions
There are no muscles in the fingers. The muscles that control finger flexion are located in the hand and forearm. Each finger has two muscles involved in flexion: flexor digitorum profundus, which attaches to the distal phalanx, and flexor digitorum superficialis, which attaches to the middle phalanx.
The flexor digitorum profundus is the main gripping muscle. It arises from the ulna and interosseous membrane and is the sole flexor of the distal interphalangeal (DIP) joint of the 2nd to 5th digits. It also acts as a flexor of the midcarpal, metacarpophalangeal, and proximal interphalangeal (PIP) joints of the index, middle, ring, and little fingers.
The flexor digitorum superficialis is an extrinsic multi-tendoned muscle that flexes the proximal interphalangeal joints of the four fingers. It comprises four digital components, each with a tendon that inserts into its corresponding finger.
