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The forearm is the region of the upper limb between the elbow and the wrist. It contains twenty muscles, divided between the anterior (flexor) and posterior (extensor) compartments. The forearm muscles are essential to the fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers. The anterior flexor compartment contains muscles such as the flexor digitorum superficialis, flexor carpi radialis, and flexor carpi ulnaris, which originate from the medial epicondyle of the humerus. These muscles flex and abduct the wrist and insert onto the bases of the metacarpals. The posterior extensor compartment contains muscles like the extensor carpi radialis longus, radialis brevis, and ulnaris, which attach to the proximal portion of the metacarpals and extend the wrist.
| Characteristics | Values |
|---|---|
| Definition | The forearm is the section of the upper limb from the elbow to the wrist |
| Bony structure | The forearm contains two long bones, the radius and the ulna, forming the two radioulnar joints |
| Muscles | The forearm has twenty muscles divided between the anterior (flexor) and posterior (extensor) compartments. Each compartment is further divided into superficial and deep compartments |
| Function | The forearm muscles are essential to the fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers |
| Flexion | The forearm can be brought closer to the upper arm due to movement at the elbow |
| Extension | The forearm can be brought away from the upper arm due to movement at the elbow |
| Pronation | The forearm can be rotated so that the palm of the hand rotates inwards due to movement at the elbow and the distal radioulnar joint |
| Supination | The forearm can be rotated so that the palm rotates outwards due to movement at the elbow and the distal radioulnar joint |
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What You'll Learn
The forearm has two long bones
The forearm is the region of the upper limb between the elbow and the wrist. The forearm has two long bones, the radius and the ulna, which form the two radioulnar joints. The radius is located on the lateral side, while the ulna is on the medial side. The interosseous membrane connects these bones. The forearm is covered by skin, with the anterior surface typically being less hairy than the posterior surface.
The forearm contains many muscles, including flexors and extensors of the wrist and digits, a flexor of the elbow (brachioradialis), and pronators and supinators that turn the hand upwards or downwards, respectively. The brachioradialis is a flexor of the forearm and is located in the posterior compartment, but it is actually part of the anterior portion of the forearm. The biceps brachii is another flexor muscle that attaches to the inner protrusion near the head of the radius and is used in lifting and pulling movements.
The forearm muscles are divided into two compartments: the anterior (flexor) and posterior (extensor) compartments, each with superficial and deep sections. The anterior flexor compartment contains the flexor digitorum superficialis, which is the largest muscle of the superficial anterior forearm muscles. It has two heads that originate from the medial epicondyle of the humerus and the radius, respectively. The muscle splits into four tendons at the wrist, flexing the metacarpophalangeal and proximal interphalangeal joints of the four fingers, as well as the wrist. The flexor carpi radialis is another muscle in the anterior compartment, originating from the medial epicondyle of the humerus and inserting onto the bases of the second and third metacarpals. It is involved in wrist flexion and abduction.
The posterior extensor compartment contains muscles such as the extensor carpi radialis longus, radialis brevis, and ulnaris, which attach to the proximal portion of the second, third, and fifth metacarpals, respectively. The extensor digitorum muscle divides into three slips, with the middle slip attaching to the middle phalanx of each digit and the collateral slips converging distally to insert at the base of the distal phalanx.
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The forearm has two muscular compartments
The forearm is the section of the upper limb between the elbow and the wrist. It contains two long bones, the radius and the ulna, forming the two radioulnar joints. The forearm has twenty muscles, which are divided between the anterior (flexor) and posterior (extensor) compartments. The anterior flexor compartment contains the flexors and is mainly supplied by the median nerve. The flexor muscles are more massive than the extensors because they work against gravity and act as anti-gravity muscles. The superficial part of the flexor surface of the forearm contains five muscles: the flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres, and flexor digitorum superficialis. The flexor digitorum superficialis is the only muscle of the intermediate compartment. It can sometimes be classed as a superficial muscle, but in most individuals, it lies between the deep and superficial muscle layers. The deep part of the flexor compartment contains three muscles: the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus.
The posterior extensor compartment contains the extensors of the hands, which are supplied by the radial nerve. The extensor compartment of the forearm is supplied with blood by the posterior interosseous artery. The superficial part of the extensor compartment contains muscles including the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor digitorum. The extensor digitorum splits into four tendons and connects to the finger joints. The deep part of the extensor compartment contains the anconeus muscle, which is considered by some as part of the posterior compartment of the arm.
The forearm muscles are essential to the fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers. They help us move our arms, hands, and fingers and perform many tasks of daily life. These muscles are also involved in our grip, and strengthening them can increase grip strength.
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The anterior forearm muscles
The forearm is the region of the upper limb between the elbow and the wrist. It contains two long bones, the radius and the ulna, forming the two radioulnar joints. The forearm can be divided into two muscular compartments: an anterior (flexor) and a posterior (extensor) compartment. The anterior forearm muscles are associated with pronation of the forearm, flexion of the wrist, and flexion of the fingers.
The superficial anterior forearm muscles are a group of five muscles located in the anterior (flexor) compartment of the forearm. These muscles include the pronator teres, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and flexor digitorum superficialis. They all originate from a common tendon, which arises from the medial epicondyle of the humerus. The majority of muscles from this group are innervated by the median nerve, except for the flexor carpi ulnaris muscle, which receives its innervation via the ulnar nerve. All of the muscles in this compartment work in synergy to produce movements of the hand and digits. More specifically, they are in charge of flexion, adduction, and abduction of the hand in the wrist joint, as well as flexion of the fingers at the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. Only the pronator teres muscle acts specifically on the proximal radioulnar joint, producing pronation of the forearm.
The flexor digitorum superficialis is the only muscle of the intermediate compartment. It can sometimes be classed as a superficial muscle, but in most individuals, it lies between the deep and superficial muscle layers. The muscle is a good anatomical landmark in the forearm – the median nerve and ulnar artery pass between its two heads, and then travel posteriorly. It has two heads – one originates from the medial epicondyle of the humerus, the other from the radius. The muscle splits into four tendons at the wrist, which travel through the carpal tunnel and attach to the base of the middle phalanx of the four digits.
There are three muscles in the deep anterior forearm: flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. The flexor digitorum profundus is the only muscle that can flex the distal interphalangeal joints of the fingers. It also flexes at metacarpophalangeal joints and at the wrist. The medial half (acts on the little and ring fingers) is innervated by the ulnar nerve, while the lateral half (acts on the middle and index fingers) is innervated by the anterior interosseous branch of the median nerve.
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The posterior forearm muscles
The forearm is the section of the upper limb between the elbow and the wrist. The forearm contains two long bones, the radius and the ulna, forming the two radioulnar joints. The forearm contains twenty muscles, divided between the anterior (flexor) and posterior (extensor) compartments. The muscles in the posterior compartment are commonly known as the extensor muscles. The general function of these muscles is to produce extension at the wrist and fingers. They are all innervated by the radial nerve.
The muscles in the posterior compartment are organised into two layers: deep and superficial. These two layers are separated by a layer of fascia. The superficial layer of the posterior forearm contains seven muscles. Four of these muscles (extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris, and extensor digiti minimi) share a common tendinous origin at the lateral epicondyle. The extensor digitorum is the major extensor muscle of digits II-V. This muscle arises from a very short common muscle belly that diverges into four individual muscle bellies, each giving rise to a single tendon. Each tendon inserts into the interconnected triangular aponeurosis (dorsal hood, extensor expansion) on the dorsal surface of each digit. The extensor digiti minimi is an accessory extensor of the little finger.
The extensor carpi radialis longus and brevis are located on the lateral aspect of the posterior forearm. Due to their position, they can produce abduction as well as extension at the wrist. The extensor carpi radialis longus has a relatively short muscle belly and a longer tendon. The extensor carpi radialis brevis is distinguishable because of its seemingly larger muscle belly, shorter tendon, and deep appearance compared to the extensor carpi radialis longus.
The anconeus is situated medially and proximally in the extensor compartment of the forearm. It is blended with the fibres of the triceps brachii, and the two muscles can be indistinguishable. It originates from the lateral epicondyle and attaches to the posterior and lateral part of the olecondyle. The anconeus extends and stabilises the elbow joint. It also abducts the ulna during pronation of the forearm.
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The forearm muscles enable complex movements
The forearm is the region of the upper limb between the elbow and the wrist. It contains two long bones, the radius and the ulna, forming the two radioulnar joints. The forearm can be divided into two muscular compartments: an anterior (flexor) and posterior (extensor) compartment. Together, these compartments contain twenty muscles that act on the elbow and wrist joints, as well as the carpometacarpal, metacarpophalangeal, and interphalangeal joints of the hand.
The forearm muscles are essential to the fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers. For example, the forearm can be brought closer to the upper arm (flexed) and brought away from the upper arm (extended) due to movement at the elbow. The forearm can also be rotated so that the palm of the hand rotates inwards (pronated) and outwards (supinated) due to movement at the elbow and the distal radioulnar joint.
The anterior flexor compartment contains the flexor digitorum superficialis, which is the largest muscle of the superficial anterior forearm muscles. It is the only muscle of the intermediate compartment and can sometimes be classed as a superficial muscle. However, in most individuals, it lies between the deep and superficial muscle layers. The flexor digitorum superficialis flexes the metacarpophalangeal joints and proximal interphalangeal joints at the four fingers, and flexes at the wrist.
The posterior extensor compartment contains the extensors of the hand, which are supplied by the radial nerve. This compartment includes muscles such as the extensor carpi radialis longus, radialis brevis, and ulnaris, which attach to the proximal portion of the second, third, and fifth metacarpals, respectively. The tendons of the extensor digitorum run under the extensor retinaculum and divide to attach to the extensor hoods of the middle and distal phalanx of each of the digits two through five.
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Frequently asked questions
The forearm is the section of the upper limb between the elbow and the wrist. It contains two long bones, the radius and the ulna, forming the two radioulnar joints.
There are twenty muscles in the forearm, divided between the anterior (flexor) and posterior (extensor) compartments. The anterior flexor compartment contains muscles such as the flexor digitorum superficialis, flexor carpi radialis, and flexor carpi ulnaris. The posterior extensor compartment contains muscles such as the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor digitorum.
The forearm muscles are essential for fine motor actions of the upper limb, allowing for complex movements of the arm, wrist, and fingers. They enable actions such as flexion, extension, pronation, and supination of the forearm, as well as flexion, extension, and abduction of the wrist.
