Dominic Stone
The human hand is a complex structure, with 30+ muscles that work together to allow for a wide range of motion. The muscles that extend the fingers are known as extrinsic extensor muscles, which are located in the back of the forearm. These include the extensor digitorum, which runs from the humerus to a common tendon attached to all fingers, and the extensor digiti minimi, which extends the little finger. The lumbrical muscles also play a role in extending the fingers, by straightening them while keeping them rigid throughout their length.
| Characteristics | Values |
|---|---|
| Number of extensor muscles in the hand | 9 |
| Location of extensor muscles | Posterior side of the forearm |
| Direction of movement | Backward |
| Extensor muscles | Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor carpi ulnaris, Extensor digitorum, Extensor indicis, Extensor pollicis brevis, Extensor pollicis longus, Extensor digiti minimi, Abductor pollicis longus |
| Function of lumbrical muscles | Allow fingers to straighten |
| Function of dorsal interossei muscles | Spread fingers apart |
| Function of palmar interossei muscles | Pull fingers together |
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What You'll Learn
The extensor digitorum extends the middle and ring fingers
The extensor digitorum muscle is a muscle of the posterior forearm that is present in humans and other animals. It is also known as the extensor digitorum communis. It extends the middle and ring fingers, as well as the other medial four digits of the hand. The extensor digitorum arises from the lateral epicondyle of the humerus, by the common tendon. From its origin, the muscle descends superficially down the posterior aspect of the forearm.
The extensor digitorum is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. The tendons of the extensor digitorum occupy the fourth extensor (dorsal) compartment. In the dorsum of the hand, the tendons of the extensor digitorum run superficial to the dorsal interossei muscles. The dorsal interossei muscles allow us to spread our fingers away from each other.
The extensor digitorum acts principally on the proximal phalanges, acting to extend the metacarpophalangeal joint. Extension of the proximal and distal interphalangeal joints is mediated predominantly by the dorsal and palmar interossei and lumbrical muscles of the hand. The main role of the lumbrical muscles is to allow the fingers to straighten, although they can also help bend the MCP joints, which are at the knuckle.
The extensor digitorum also participates in the extension of the wrist. The contraction of the extensor digitorum across the wrist joint contributes to its extension. The extensor digitorum has been found to play a role in the pathology of lateral epicondylitis due to its role in the extension of the middle finger, which reproduces pain on resisted extension.
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The extensor digiti minimi extends the little finger
The extensor digitorum is a muscle that extends the fingers. It is divided into four tendons that run along the back of the hand and connect to the fingers. One of these tendons is the extensor digiti minimi, which is responsible for extending the little finger.
The extensor digiti minimi is a long, thin muscle found in the posterior forearm. It is part of the extrinsic extensor muscles of the hand, which are located in the back of the forearm and have long tendons connecting them to bones in the hand. These muscles extend or open flat the joints in the hand.
The extensor digiti minimi arises from the common extensor tendon and is connected to the extensor digitorum communis muscle. From the middle of the forearm, its fibres are clearly separated from the extensor digitorum. It then continues as a long tendon that passes deep into the extensor retinaculum and enters the dorsal aspect of the hand.
The tendon from the extensor digiti minimi splits into two slips as it crosses the back of the hand. These slips fuse with the tendons of the extensor digitorum and ultimately attach to the extensor expansion of the fifth digit, or the little finger. This allows the extensor digiti minimi to extend the little finger, straightening it from a clenched fist.
The index finger and little finger have separate extensors, allowing them to move more independently than the other fingers. The extensor digiti minimi is an important muscle that enables precise movements and dexterity in the hand.
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The abductor digiti minimi abducts the little finger
The abductor digiti minimi is a muscle that moves the little finger away from the rest of the fingers. Located on the ulnar side of the palm, it forms the ulnar border, marking the hypothenar eminence of the palm with the skin, fat, and connective tissue that covers it. The abductor digiti minimi is derived from the ulnar muscle primordium of the superficial layer of the original undifferentiated mesenchyme of the hand. It develops alongside the abductor pollicis brevis and the flexor digitorum superficialis.
The abductor digiti minimi is the most variable hypothenar muscle and may be joined by accessory slips from the tendon of the flexor carpi ulnaris, the flexor retinaculum, and the fascia of the antebrachial fascia. In rare cases, it has been found to arise from the antebrachial fascia, the radius, and the ulna. The muscle originates from the pisohamate ligament, pisiform bone, and flexor retinaculum, inserting at the base of the proximal phalanx of the little finger on the medial or ulnar side.
The abductor digiti minimi is one of three muscles that make up the hypothenar muscle group, along with the flexor digiti minimi and the opponens digiti minimi. These muscles form the muscle bulk on the small finger side of the hand. The abductor digiti minimi is also one of the extrinsic extensor muscles of the hand, which are located in the back of the forearm and have long tendons connecting them to bones in the hand. These muscles extend or open flat the joints in the hand.
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The flexor digiti minimi flexes the little finger
The flexor digiti minimi brevis is a hypothenar muscle in the hand that flexes the little finger at the metacarpophalangeal joint. The word "hypothenar" refers to the hump at the base of the fifth digit, also known as the little finger. The flexor digiti minimi brevis is one of three muscles in the hypothenar muscle group, which form the fleshy mass at the base of the little finger. These muscles are solely concerned with the movement of the little finger.
The main function of the flexor digiti minimi brevis is to flex the little finger, allowing it to bend at the MCP joint. It also participates in lateral rotation and opposition of the little finger, enabling movements such as cupping the hand and bringing the little finger towards the thumb. The flexor digiti minimi brevis lies lateral to the abductor digiti minimi when the hand is in the anatomical position.
The flexor digiti minimi brevis arises from the hamulus of the hamate bone and the palmar surface of the flexor retinaculum of the hand. It is inserted into the medial side of the base of the proximal phalanx of the little finger. The ulnar nerve and the deep branches of the ulnar artery separate it from the abductor digiti minimi at its origin. In some cases, the flexor digiti minimi brevis may be absent, resulting in a larger than normal abductor digiti minimi.
The flexor digiti minimi brevis is an important muscle for the movement and function of the little finger. It works in conjunction with the other muscles in the hypothenar muscle group to allow for a range of motions and grip positions in the hand.
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The opponens digiti minimi rotates the fifth metacarpal
The muscles in our body are groups of cells that have the ability to contract and relax. Some muscles are controlled automatically by the autonomic nervous system, while others, like skeletal muscles, are controlled by the somatic or voluntary nervous system. The hand contains extrinsic extensor muscles, which are located in the back of the forearm and have long tendons connecting them to bones in the hand. These muscles include the extensor digitorum (ED), extensor digiti minimi (EDM), and abductor digiti minimi.
The opponens digiti minimi (ODM) is an intrinsic muscle of the hand. It is one of three hypothenar muscles that control the little finger, arising from the convexity of the hamulus of the hamate bone and the transverse carpal ligament. The ODM is a triangular muscle that extends between the hamate bone (carpal bone) and the 5th metacarpal bone, inserting into the entire length of the ulnar border of the 5th metacarpal.
The ODM acts in conjunction with the abductor digiti minimi and flexor digiti minimi brevis to move the little finger. The abductor digiti minimi allows the small finger to pull away from the ring finger, while the flexor digiti minimi brevis enables the small finger to bend at the MCP joint. The opponens digiti minimi is innervated by the deep branch of the ulnar nerve, which passes through the hook of hamate and pisiform bone (Guyon's canal).
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Frequently asked questions
The extrinsic extensor muscles of the hand are the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum, extensor digiti minimi, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.
The extensor digitorum muscle runs from the humerus to a common tendon attached to all the fingers and extends the fingers.
The extensor digiti minimi muscle abducts the little finger, allowing it to spread the fingers apart.
The extensor pollicis brevis muscle extends the thumb.
