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The interossei muscles are found in the hand and foot. They are divided into two groups: the palmar interossei and the dorsal interossei. The palmar interossei are three short, unipennate muscles on the palmar surface of the hand, occupying the spaces between the metacarpal bones. They are strong adductors of the fingers, pulling them towards the middle finger. The dorsal interossei, on the other hand, are abductors of the fingers, moving them away from the axis of the middle finger. They consist of four short muscles that attach to the adjacent sides of metacarpals 1-4.
| Characteristics | Values |
|---|---|
| Type | Palmar interossei, Dorsal interossei |
| Location | Palmar interossei: palmar surface of the hand, between the metacarpal bones; Dorsal interossei: dorsal compartment of the hand, between the metacarpal bones |
| Function | Palmar interossei: adduct fingers; Dorsal interossei: abduct fingers |
| Innervation | Deep branch of ulnar nerve |
| Blood supply | Palmar interossei: palmar metacarpal arteries; Dorsal interossei: dorsal and palmar interossei artery |
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What You'll Learn
Palmar interossei muscles are found in the hand
The palmar interossei are intrinsic muscles of the hand. They are situated on the palmar surface of the hand and occupy the spaces between the metacarpal bones. They are smaller than the dorsal interossei.
The palmar interossei consist of four muscles, numbered 1–4 from the lateral to the medial side. The first palmar interosseous, or pollical palmar interosseous, is often considered rudimentary and may not always be present. It originates at the medial palmar surface of the first metacarpal and inserts into the base of the proximal phalanx and extensor hood of the first digit. The second palmar interosseous originates from the medial surface of the base of the second metacarpal and inserts into the medial portion of the extensor hood and base of the proximal phalanx of the second digit. The third and fourth palmar interossei originate from the lateral aspects of the fourth and fifth metacarpals, respectively, and insert into the lateral extensor hood and base of the proximal phalanx of their corresponding digits.
The main function of the palmar interossei is to adduct the fingers in a longitudinal axis, which means moving the fingers towards the middle finger. Specifically, the first palmar interosseous pulls the index finger medially, while the second and third pull the ring and little fingers laterally. The palmar interossei also assist in flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal joints. They receive innervation from the deep branch of the ulnar nerve, and their blood supply comes from branches of the deep palmar arch and various palmar arteries.
Injury to the ulnar nerve can result in weakness or atrophy of the palmar interossei muscles. Ulnar nerve entrapment is a common issue that may lead to weakness in adduction of the fingers. The strength of the palmar interossei muscles can be tested by asking a patient to hold a sheet of paper between their second through fifth digits; dropping the paper may indicate palmar interossei weakness.
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Dorsal interossei muscles are found in the hand
The dorsal interossei muscles are four small, short, bipennate intrinsic muscles of the hand. They are found on the dorsal aspect of the hand, occupying the space between the metacarpal bones, alongside the palmar interossei muscles.
The dorsal interossei muscles consist of four short muscles that attach to the adjacent sides of metacarpals 1-4. They are innervated by the deep branch of the ulnar nerve (C8, T1) and are supplied by the dorsal and palmar interossei artery. The first dorsal interosseous is larger than the others and can be easily felt in the web between the thumb and index finger. The remaining three can be palpated between the metacarpal bones and the tendon of the extensor digitorum muscle.
The function of the dorsal interossei is to abduct the index, middle, and ring fingers, as well as to assist in flexion of these fingers at the metacarpophalangeal (MCP) joints and in extension at the interphalangeal (IP) joints. They also contribute to stabilisation of these joints. The first dorsal interosseous is also able to rotate the index finger slightly at the MCP joint and assist the adductor pollicis in thumb adduction.
The dorsal interossei muscles can be tested by placing the patient's palm flat on a table and asking them to abduct their index finger against resistance. This is a reliable test for the ulnar nerve.
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The function of the palmar interossei
The palmar interossei are intrinsic muscles of the hand that occupy the spaces between the metacarpal bones. They are strong adductors of the fingers, meaning they bring the fingers towards the centre or the middle finger. Specifically, the first palmar interosseous pulls the index finger medially, while the second and third pull the ring and little fingers laterally.
The palmar interossei are smaller than the dorsal interossei of the hand. They receive arterial blood supply from the palmar metacarpal arteries and drain into the palmar metacarpal veins. The palmar metacarpal arteries derive from the deep palmar arch, which is made up of the terminal portion of the radial artery and the deep branch of the ulnar artery.
The palmar interossei receive nerve supply from the deep branch of the ulnar nerve. Injury to the ulnar nerve can result in weakness or atrophy of the interossei muscles. Ulnar nerve entrapment is a common issue, which may cause weakness in adduction of the fingers.
The palmar interossei also assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints of the second, fourth, and fifth fingers.
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The function of the dorsal interossei
The interossei muscles are categorised into two groups: palmar interossei and dorsal interossei, with four muscles in each group. The function of the dorsal interossei is to abduct the second, third and fourth digits, or fingers. The first dorsal interosseous muscle can be tested by placing a patient's palm flat on a table and asking them to abduct their index finger against the examiner's resistance. The muscle belly can be seen and palpated and is a reliable test for the ulnar nerve.
The dorsal interossei muscles are bipennate in shape, extending from the proximal ends of adjacent metacarpals to the proximal phalanx and dorsal digital expansion of the appropriate finger. The position of the insertion site depends on which digit is involved. On the first and second digits, the muscle lies on the lateral side, and on the third and fourth digits, it lies on the medial side.
The dorsal interossei muscles are larger than the palmar interossei and are situated on the dorsum of the hand, in between the metacarpal bones. The dorsal interossei muscles of the foot are four feather-like muscles found in the central compartment of the sole of the foot. They are two-headed muscles found between the metatarsal bones that flex, adduct and extend the toes. They also contribute to the stability of the foot by supporting the anterior metatarsal, medial and lateral arches of the foot in activities such as running, walking and jumping.
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Innervation of the interossei muscles
The interossei muscles are intrinsic muscles of the hand that occupy the spaces between the metacarpal bones. The palmar interossei muscles are smaller than the dorsal interossei and are situated on the palmar surface of the hand. The dorsal interossei, on the other hand, are located superficially on the dorsum of the hand and can be palpated between the metacarpal heads.
Both the palmar and dorsal interossei muscles are innervated by the deep branch of the ulnar nerve, derived from roots C8 and T1. The ulnar nerve is responsible for supplying both types of interossei muscles, which play a crucial role in hand function and movement.
The palmar interossei muscles receive their arterial blood supply from various branches of the deep palmar arch, including the princeps pollicis artery, radialis indicis artery, palmar metacarpal arteries, proximal and distal perforating arteries, and common and proper palmar arteries. This blood supply is essential for maintaining the health and function of the palmar interossei muscles.
In contrast, the dorsal interossei muscles are supplied by the dorsal and palmar interossei arteries. These arteries ensure adequate blood flow to the dorsal interossei muscles, enabling them to function properly during hand movements.
Any injury or compression of the ulnar nerve can lead to weakness or atrophy of the interossei muscles. Ulnar nerve entrapment, for example, can cause patients to experience weakness in adduction of the fingers, affecting their ability to perform fine motor tasks and grip objects firmly.
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Frequently asked questions
The interossei muscles are muscles found near the metacarpal bones that help to control the fingers.
The palmar interossei muscles are three short, unipennate intrinsic muscles on the palmar surface of the hand.
The dorsal interossei muscles are situated within the dorsal compartment of the hand. They lie deep to the palmar interossei, filling the interosseous space.
The palmar interossei muscles adduct the fingers in a longitudinal axis, which means they move the fingers towards the middle finger.
The dorsal interossei muscles abduct the fingers 2-4 in a longitudinal axis, moving them away from each other.
