Logan Steele
The interossei muscles are intrinsic muscles of the hand located between the metacarpal bones. They consist of four or three palmar interossei and four dorsal interossei muscles. The palmar interossei are short unipennate muscles that lie on the palmar surface of the hand. The dorsal interossei are short bipennate muscles found on the dorsal aspect of the hand. These muscles are responsible for finger adduction and abduction, as well as flexion of the metacarpophalangeal joints and extension of the interphalangeal joints.
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What You'll Learn
- The interossei muscles are located between the metacarpal bones of the hand
- They consist of four (or three) palmar and four dorsal muscles
- The palmar interossei are short, unipennate intrinsic muscles of the hand
- The dorsal interossei are four small, bipennate intrinsic muscles of the hand
- Any injury to the ulnar nerve may have implications on specific intrinsic hand muscle functions
The interossei muscles are located between the metacarpal bones of the hand
The interossei muscles are intrinsic muscles of the hand located between the metacarpal bones. They consist of four (or sometimes three) palmar interossei and four dorsal interossei muscles. The palmar interossei are short unipennate muscles that lie on the palmar surface of the hand. They attach to the 1st, 2nd, 4th, and 5th fingers, with the one on the 1st finger sometimes being rudimentary. The first palmar interosseous muscle, also known as the "pollical palmar interosseous" (PPI) muscle, was found to be present in 93% of hands in one study. The second palmar interosseous arises from the entire length of the 2nd metacarpal bone and inserts into the extensor expansion of the index finger.
The dorsal interossei muscles are short bipennate intrinsic muscles found on the dorsal aspect of the hand. They consist of four small muscles that attach to the adjacent sides of metacarpals 1-4. The first dorsal interosseous can be felt in the web between the thumb and index finger, and the remaining three can be palpated between the metacarpal bones and the tendon of the extensor digitorum muscle. The dorsal interossei receive their blood supply from the dorsal carpal anastomosis, with the first receiving supply from the radial artery.
The interossei muscles are responsible for finger adduction and abduction. The palmar interossei are strong adductors of the fingers, while the dorsal interossei abduct the 2nd, 3rd, and 4th fingers. Additionally, the interossei assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints. They also play a key role in hand function, including grip and pinch. The interossei muscles receive innervation from the deep ulnar branch of the ulnar nerve, so any injury to this nerve can have significant implications on hand muscle functions.
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They consist of four (or three) palmar and four dorsal muscles
The interossei muscles are intrinsic muscles of the hand located between the metacarpals. They consist of four (or sometimes three) palmar and four dorsal muscles. The palmar interossei are short, unipennate muscles of the palmar surface of the hand. They consist of four muscles that attach to the 1st, 2nd, 4th, and 5th fingers, with the one on the 1st finger sometimes being rudimentary. The first palmar interosseous muscle, or "pollical palmar interosseous" (PPI) muscle, was found to be present in 93% of hands in one study. The second palmar interosseous arises from the entire length of the 2nd metacarpal bone and is inserted into the extensor expansion of the index finger.
The dorsal interossei are short, bipennate intrinsic muscles of the hand. They are found on the dorsal aspect of the hand, occupying the space between the metacarpal bones. The four short muscles attach to the adjacent sides of metacarpals 1-4. The first dorsal interosseous can be felt in the web between the thumb and index finger, and the remaining three can be palpated between the metacarpal bones and the tendon of the extensor digitorum muscle. The dorsal interossei abduct the 2nd, 3rd, and 4th fingers, assisting in flexion and extension at the interphalangeal joints.
The palmar and dorsal interossei work synchronously to assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints. They are also responsible for finger adduction and abduction. 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.
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The palmar interossei are short, unipennate intrinsic muscles of the hand
The palmar interossei consist of four muscles that attach to the first, second, fourth, and fifth fingers. The third finger does not contain a palmar interosseous muscle. The first palmar interosseous muscle is sometimes rudimentary, and some sources describe a fourth muscle at the base of the proximal phalanx of the thumb. These muscles are strong adductors of the fingers and assist in flexion and extension of the second, fourth, and fifth fingers.
The origin of the word 'unipennate' is worth noting. A pennate muscle is one that attaches obliquely to its tendon. The '-uni-' prefix indicates that the muscle fibres converge to attach on one side of the tendon. The palmar interossei are unipennate muscles that originate from the metacarpals of the respective digits to which they are associated.
The palmar interossei muscles receive arterial blood supply from branches of the deep palmar arch and various palmar arteries. They are innervated by the deep branch of the ulnar nerve, derived from roots C8 and T1. As such, any injury to the ulnar nerve may impair specific intrinsic hand muscle functions, including finger adduction, which is primarily controlled by the palmar interossei.
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The dorsal interossei are four small, bipennate intrinsic muscles of the hand
The interossei muscles are intrinsic muscles of the hand located between the metacarpals. They consist of four (or three) palmar and four dorsal muscles. The dorsal interossei are four small, bipennate intrinsic muscles of the hand. They are found on the dorsal aspect of the hand occupying the space between the metacarpal bones, along with the palmar interossei muscles. The dorsal interossei muscles consist of four short muscles that attach to the adjacent sides of metacarpals 1-4.
The prefix "bi-" means that they arise by two heads which converge to attach onto a central tendon, giving them a feather-like shape. The four dorsal interossei muscles are numbered 1–4 from the lateral to the medial side. The first dorsal interosseous muscle is the largest and strongest of the dorsal interossei and is sometimes referred to as abductor indicis. It arises from the adjacent surfaces of the first and second metacarpal bones. The muscle fibres converge distally into a tendon, which inserts on the radial side of the base of the second proximal phalanx and its dorsal digital expansion. The second dorsal interosseous muscle arises from the adjacent surfaces of the second and third metacarpal bones. Like the first muscle, the muscle fibres of the second dorsal interosseous converge distally into a tendon, which inserts on the radial side of the base of the third proximal phalanx and its dorsal digital expansion.
The main function of the dorsal interossei is to abduct the fingers 2-4 in a longitudinal axis, moving them away from each other. The dorsal interossei 1-2 pull the digits 2-3 laterally (radial abduction), while the dorsal interossei 3-4 move the digits 3-4 medially (ulnar abduction). The third digit can be abducted both medially and laterally depending on which dorsal interosseous muscle contracts. The dorsal interossei also assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints. All interossei muscles receive innervation by the deep ulnar branch of the ulnar nerve.
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Any injury to the ulnar nerve may have implications on specific intrinsic hand muscle functions
The interossei muscles are intrinsic muscles of the hand located between the metacarpal bones. They consist of four or three palmar and four dorsal muscles. These muscles are responsible for finger adduction and abduction, flexion of the metacarpophalangeal joints, and extension of the interphalangeal joints.
The ulnar nerve is a major peripheral nerve of the upper limb. It supplies all intrinsic muscles of the hand except the lateral two lumbricals, opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis. The ulnar nerve is clinically significant for its role in hand function, as it innervates the majority of intrinsic hand muscles.
Any injury to the ulnar nerve may result in sensory and motor deficits within the hand. This can lead to paresthesia, dysesthesia, muscle weakness, and altered sensations in the affected hand. Specifically, ulnar nerve injuries can cause paralysis of the interossei muscles, resulting in an inability to perform finger abduction and adduction. This is because the interossei muscles are innervated by the deep ulnar branch of the ulnar nerve.
The functional outcome following repair of the ulnar nerve has been traditionally poor, especially in high ulnar nerve injuries, where the nerve is damaged above the origin of the motor branch of the flexor carpi ulnaris and flexor digitorum profundus muscles. Early neurorrhaphy of acute nerve injuries provides the best outcome, and distal motor nerve transfers can be performed to preserve hand intrinsic motor function. More recently, distal nerve transfers, such as the anterior interosseous nerve (AIN) transfer to the ulnar motor branch, have been recommended as an alternative to restore intrinsic function.
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Frequently asked questions
The interossei muscles are intrinsic muscles of the hand located between the metacarpals. They consist of four or three palmar and four dorsal muscles.
The two types of interossei muscles are the palmar interossei and the dorsal interossei muscles.
The interossei muscles are responsible for finger adduction and abduction. They also assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints.
The palmar interossei are short unipennate intrinsic muscles of the hand. They consist of four muscles that attach to the 1st, 2nd, 4th, and 5th fingers.
The dorsal interossei muscles are short bipennate intrinsic muscles of the hand. They consist of four small muscles that attach to the adjacent sides of metacarpals 1-4.
