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The forearm is the section of the upper limb between the elbow and the wrist, with twenty muscles that act on the elbow and wrist joints, as well as carpometacarpal, metacarpophalangeal, and interphalangeal joints of the hand. These muscles are divided into two compartments: the anterior (flexor) and the posterior (extensor) compartments. The muscles in the anterior compartment are the forearm flexors, which are responsible for flexion and pronation at the wrist, and flexion of the fingers.
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What You'll Learn
The forearm has 20 muscles
The forearm is the section of the upper limb between the elbow and the wrist. It contains 20 muscles that work together to move the elbow, forearm, wrist, and digits of the hand. These muscles are supported by the two forearm bones, the ulna and radius, which form a joint that rotates to let you turn the palm of your hand up or down.
The forearm muscles are divided into two muscular compartments: the anterior (flexor) compartment and the posterior (extensor) compartment. The anterior compartment contains muscles that engage in the flexion of the arms and hands. The muscles in this compartment include the flexor digitorum superficialis, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and pronator teres. The deep anterior forearm muscles include the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. The flexor digitorum profundus allows you to bend your ring, middle, index, and pinkie fingers, while the flexor pollicis longus allows you to bend your thumb.
The posterior compartment contains the extensors and supinators of the forearm. The muscles in this compartment include the extensor carpi radialis longus and brevis, which extend the wrist and move the hand away from the direction of the thumb. The extensor digitorum splits into four tendons and connects to the finger joints, helping to straighten or extend the fingers.
The muscles of the forearm are innervated by three main nerves: the median, ulnar, and radial nerves. The median nerve innervates the muscles of the flexor compartment, while the radial nerve innervates the muscles of the extensor compartment. The ulnar nerve provides innervation for both compartments.
The forearm muscles are involved in many daily tasks, such as carrying groceries or playing sports. Strengthening these muscles can increase grip strength and improve performance in exercises such as rows, kettlebell swings, deadlifts, and bicep curls. However, it is important to be cautious as muscle strains can occur if the forearm muscles are overloaded or overused.
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Forearm muscles are divided into two compartments
The forearm is the section of the upper limb from the elbow to the wrist. The forearm muscles are divided into two compartments: the anterior (flexor) and the posterior (extensor). These compartments contain twenty muscles that act on the elbow and wrist joints, as well as 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.
The anterior compartment is also known as the flexor compartment. It contains three layers of muscle: superficial, intermediate, and deep. The superficial group contains four muscles, all originating from a common tendon on the medial epicondyle of the humerus. These are pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. The intermediate group contains only one muscle, flexor digitorum superficialis. The deep group has three muscular components: flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. The flexor digitorum profundus allows you to bend your ring, middle, index, and pinkie fingers. The flexor pollicis longus allows you to bend your thumb. The pronator quadratus is a square-shaped muscle that lets you turn your forearm downward.
The posterior compartment is also known as the extensor compartment. The superficial part of the extensor compartment contains seven muscles. The muscles in this compartment arise from the lateral epicondyle of the humerus, also known as the common extensor origin. The muscles in the posterior compartment include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, anconeus, and extensor pollicis longus. The extensor carpi radialis longus, radialis brevis, and ulnaris attach to the proximal portion of the second, third, and fifth metacarpals, respectively. The extensor digitorum splits into four tendons and connects to the finger joints, helping to straighten or extend the fingers. The extensor digiti minimi extends the little finger. The extensor carpi ulnaris helps to turn and extend the wrist. The anconeus, near the top of the superficial layer, helps extend the forearm at the elbow.
The two compartments are separated by the two forearm bones and a membrane. The interosseous membrane bridges the gap between the two bones. The interosseous membrane also separates the anterior interosseous branch, which supplies blood to the muscles of the flexor compartment, from the posterior interosseous artery, which supplies blood to the extensor compartment. The median and ulnar nerves provide innervation for the muscles of the flexor compartment, while the radial nerve provides innervation for the extensor compartment.
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The anterior compartment contains flexors
The forearm is divided into two muscular compartments: the anterior (flexor) compartment and the posterior (extensor) compartment. Together, these compartments contain 20 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 broadly responsible for the extension and movement of the wrists and fingers.
The anterior compartment is divided into three groups, or layers: superficial, intermediate, and deep. The superficial muscles include the pronator teres, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and flexor digitorum superficialis. The flexor digitorum superficialis is the largest muscle of the superficial anterior forearm muscles. It consists of two heads: the humeroulnar head, which originates from the medial epicondyle of the humerus and the coronoid process of the ulna, and the radial head, which originates from the shaft of the radius. The muscle splits into four tendons that pass behind the flexor retinaculum and insert onto the middle phalanges of digits 2-5. The prime function of the flexor digitorum superficialis is flexion of the digits 2-5 at the PIP and MCP joints, as well as contributing to the flexion of the hand at the wrist joint.
The deep muscles of the anterior forearm include the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. The flexor digitorum profundus allows you to bend your ring, middle, index, and pinkie fingers, while the flexor pollicis longus allows you to bend your thumb. The pronator quadratus is a square-shaped muscle that lets you turn your forearm downward.
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The flexor digitorum superficialis is the largest muscle
The forearm is the section of the upper limb between the elbow and the wrist. It contains twenty muscles that act on the elbow and wrist joints, as well as carpometacarpal, metacarpophalangeal, and interphalangeal joints of the hand. These muscles are divided into two compartments: the anterior flexor compartment and the posterior extensor compartment.
The humeroulnar head originates from the medial epicondyle of the humerus via the common flexor tendon, as well as the medial margin of the coronoid process of the ulna. Some fibres also originate from the anterior band of the ulnar collateral ligament of the elbow joint. The radial head arises from the upper two-thirds of the anterior border of the radius. The muscular heads of the flexor digitorum superficialis course distally across the anterior forearm.
The flexor digitorum superficialis has four long tendons that originate near the wrist and travel through the carpal tunnel formed by the flexor retinaculum. These tendons attach to the middle phalanges of fingers 2 to 5. The flexor digitorum superficialis flexes fingers 2 to 5, as when making a fist. The primary function of the muscle is flexion of the middle phalanges of the four fingers (excluding the thumb) at the proximal interphalangeal joints. However, under continued action, it also flexes the metacarpophalangeal joints and wrist joint.
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Median nerve innervation
The median nerve is a sensory and motor nerve of the arm, arising from the lateral and medial cords of the brachial plexus, which originates in the spinal cord. The nerve travels between the two heads of the pronator teres, then descends between the flexor digitorum profundus and flexor digitorum superficialis muscles.
The median nerve is one of three nerves that innervate the skin, along with the medial and lateral cutaneous nerves. It innervates several muscles in the forearm and hand, providing signals to and from the brain and spinal cord. This allows for two-way communication between the brain and muscles, enabling the brain to send instructions for specific actions and receiving sensory information, such as heat and pain, from the muscles.
The median nerve gives rise to two major branches in the forearm: the anterior interosseous nerve and the palmar cutaneous nerve. The anterior interosseous nerve supplies the deep muscles in the anterior forearm, while the palmar cutaneous nerve innervates the skin of the lateral palm.
The median nerve directly innervates muscles in the superficial and intermediate layers of the forearm. In the superficial layer, it innervates the pronator teres, flexor carpi radialis, and palmaris longus. In the intermediate layer, it innervates the flexor digitorum superficialis. The median nerve also gives rise to the anterior interosseous nerve, which supplies the deep flexors in the forearm. In the deep layer, it innervates the flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus.
Distal branches of the median nerve supply innervation to the lumbrical muscles located in the index and middle fingers, while the recurrent branch of the median nerve innervates the thenar muscles, which are associated with movements of the thumb.
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Frequently asked questions
The forearm muscles are responsible for the extension and movement of your wrists and fingers. They also help you move your arms and hands and perform many tasks of daily life.
There are 20 muscles in the forearm, the part of your arm between your elbow and your hand.
The forearm is divided into two muscular compartments: the anterior (flexor) compartment and the posterior (extensor) compartment.
The muscles in the anterior (flexor) compartment include the flexor digitorum superficialis, flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and pronator teres.
