Dominic Stone
The intrinsic muscles of the hand are located within the hand itself and are responsible for the hand's fine motor functions. These muscles are innervated by the radial, median, and ulnar nerves. The radial nerve innervates the finger extensors and the thumb abductor, while the median nerve innervates the flexors of the wrist and digits, and the ulnar nerve innervates the remaining intrinsic muscles of the hand. The hand muscles are also innervated by the brachial plexus (C5–T1), with some sources specifically mentioning C8 and T1 roots.
| Characteristics | Values |
|---|---|
| Innervation | Ulnar nerve, Median nerve, C8 and T1 roots |
| Function | Responsible for the fine motor functions of the hand |
| Muscles | Adductor pollicis, Palmaris brevis, Hypothenar muscles, Thenar muscles, Interossei muscles, Lumbricals |
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What You'll Learn
- The ulnar nerve innervates most of the intrinsic muscles in the hand
- The median nerve innervates the remaining intrinsic muscles
- Median nerve injuries are referred to as high or low
- Ulnar nerve injuries are also referred to as high or low
- All muscles of the hand are innervated by the brachial plexus (C5–T1)
The ulnar nerve innervates most of the intrinsic muscles in the hand
The muscles of the hand are innervated by the radial, median, and ulnar nerves. The radial nerve innervates the finger extensors and the thumb abductor, controlling the muscles that extend at the wrist and metacarpophalangeal joints (knuckles) and abduct and extend the thumb. The median nerve, meanwhile, innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, and the first and second lumbricals.
The ulnar nerve, however, innervates most of the intrinsic muscles in the hand. It is the distal continuation of the medial cord of the brachial plexus, from the nerve roots of C8 and T1. The ulnar nerve provides motor innervation to various muscles of the forearm and hand, as well as sensory supply to the skin of the hand. It is often referred to as the nerve of the hand due to its clinically apparent role in hand function.
The ulnar nerve gives rise to two muscular branches in the forearm: one that innervates the flexor carpi ulnaris and another that innervates the ulnar (medial) part of the flexor digitorum profundus. As the nerve descends into the forearm, it continues to give branches to the flexor digitorum profundus and stays medially above the muscle. The ulnar nerve also gives rise to two cutaneous branches in the forearm: the palmar cutaneous nerve and the dorsal cutaneous nerve.
At the wrist, the ulnar nerve travels superficially to the flexor retinaculum and is medial to the ulnar artery. It enters the hand via the ulnar canal (Guyon's canal) and divides into superficial (sensory) and deep (motor) branches. The deep branch of the ulnar nerve innervates the three hypothenar muscles, the two medial lumbricals, the seven interossei, the adductor pollicis, and the deep head of the flexor pollicis brevis.
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The median nerve innervates the remaining intrinsic muscles
The median nerve is one of the five main nerves originating from the brachial plexus. It is a major peripheral nerve of the upper limb, arising from the lateral and medial cords of the brachial plexus and terminating by supplying the muscles of the hand. The median nerve is responsible for the cutaneous innervation of part of the hand.
The median nerve innervates the 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 deep layer, it innervates the flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus. The median nerve also innervates the thenar muscles and the first and second lumbricals.
The median nerve is the only nerve that passes through the carpal tunnel, a narrow passageway in the palm-side of the wrist. Carpal tunnel syndrome is a disability that results from the median nerve being pressed in this tunnel. The syndrome is often associated with pain, tingling, and numbness in the hand and arm. It can cause atrophy or wasting of the muscles in the thenar eminence due to a lack of stimulation from the median nerve.
The median nerve also gives off sensory and other branches in the forearm. The palmar cutaneous branch of the median nerve arises at the distal part of the forearm and supplies sensory innervation to the thenar eminence of the palm and the central palm. The digital cutaneous branch innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.
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Median nerve injuries are referred to as high or low
The median nerve is one of three nerves that innervate the muscles of the hand. The nerve begins in the axillary region, with its root situated in the anterior rami of C5-T1. It descends through the arm, lying lateral to the brachial artery. At the level of the insertion of the Coracobrachialis, it crosses the artery and lies on its medial side at the bend of the elbow. The median nerve is particularly vulnerable to injury at the wrist, where it passes through the carpal tunnel.
Median nerve injuries are referred to as "high" or "low" depending on the site of injury and the symptoms. The two most common places for the median nerve to become damaged or compressed are at the elbow and at the wrist. At the elbow, injuries such as fractures or dislocations can cause nerve damage. This can result in conditions such as pronator teres syndrome, which causes a dull, aching pain in the forearm and may also lead to thumb and finger numbness or paralysis.
At the wrist, carpal tunnel syndrome is a common condition caused by pressure on the median nerve as it passes through the carpal tunnel. This can result in a tingling sensation, numbness, and sometimes pain in the hand and fingers, particularly affecting the thumb, index finger, and middle finger. The symptoms usually develop gradually and are worse at night. Other symptoms of carpal tunnel syndrome can include dull forearm pain and sensory loss in the affected area, where the skin may feel warm and dry.
In addition to these common injury sites, median nerve injuries can also occur due to posture, workplace ergonomics, direct trauma, or physiological conditions such as pregnancy. Diagnosis of median nerve injuries typically involves a physical examination, including tests such as the Phalen sign and Tinel sign, which are highly suggestive of nerve entrapment. X-ray and ultrasound can also aid in diagnosis, while electromyography (EMG) can help quantify the location and extent of nerve damage. Treatment options include conservative approaches such as adjusting workplace ergonomics, using braces, and physiotherapy, as well as surgical procedures in more severe cases.
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Ulnar nerve injuries are also referred to as high or low
The muscles of the hand are innervated by the radial, median, and ulnar nerves. The ulnar nerve is responsible for innervating the remaining intrinsic muscles of the hand. Ulnar nerve injuries are referred to as high or low depending on the site of compression along the nerve. The ulnar nerve has several potential compression sites along its course, with the elbow being the most common site, followed by the wrist, forearm, and upper arm.
High ulnar nerve injuries refer to injuries at the elbow, which is the most common site of compression. Cubital tunnel syndrome, also known as ulnar nerve entrapment at the elbow, occurs when the ulnar nerve is compressed within the cubital tunnel. This can be caused by repetitive elbow flexion and extension, arthritic changes, valgus deformities, or leaning on the elbows for prolonged periods. Symptoms of high ulnar nerve injuries include a tingling sensation in the "funny bone," weakness in the grip, pain, and sensitivity on the ulnar side of the forearm, wrist, and hand.
Low ulnar nerve injuries refer to injuries at the wrist, which is a less common site of compression. Guyon's canal syndrome, also known as ulnar nerve entrapment at the wrist, occurs when the ulnar nerve becomes entrapped between the hook of the hamate and the transverse carpal ligament. This can be caused by direct pressure on handlebars, excessive gripping or twisting, repeated wrist and hand motions, or prolonged periods of wrist flexion and ulnar deviation. Symptoms of low ulnar nerve injuries include tingling in the fingers, muscle atrophy, clawing of the fourth and fifth digits, and sensory loss or pain in the affected areas.
It is important to note that ulnar nerve injuries are susceptible to external compression and early diagnosis and treatment are crucial for a positive prognosis. Conservative treatments, such as reducing external compression, physical therapy, and the use of elbow splints or pads, can help manage ulnar nerve injuries. However, if nonsurgical treatments are ineffective, surgery may be required to release the pinched ulnar nerve.
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All muscles of the hand are innervated by the brachial plexus (C5–T1)
The muscles of the hand are innervated by the radial, median, and ulnar nerves. The radial nerve innervates the finger extensors and the muscles that extend at the wrist and metacarpophalangeal joints (knuckles), allowing for thumb abduction and extension. The median nerve innervates the flexors of the wrist and digits, the abductors and opponens of the thumb, and the first and second lumbricals. The ulnar nerve innervates the remaining intrinsic muscles of the hand.
The anterior divisions of the upper and middle trunks unite to form the lateral cord, which gives rise to the lateral pectoral nerve (C5, C6, and C7). This nerve supplies the pectoralis major muscle. The anterior division of the lower trunk forms the medial cord, which gives rise to the medial pectoral nerve (C8, T1), the medial brachial cutaneous nerve (T1), and the medial antebrachial cutaneous nerve (C8, T1). These nerves provide sensory innervation to the skin of the arm and forearm.
The posterior divisions of each of the three trunks unite to form the posterior cord. The upper (C7, C8) and lower (C5, C6) subscapular nerves leave the posterior cord and supply the subscapularis and teres major muscles. The cords continue to give rise to major terminal branches of the brachial plexus, including the radial, axillary, median, ulnar, and musculocutaneous nerves. These nerves innervate various muscles of the upper limb and provide sensory functions.
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Frequently asked questions
Intrinsic muscles are located within the hand itself and are responsible for the fine motor functions of the hand.
The ulnar nerve innervates most of the intrinsic muscles in the hand. The remaining intrinsic muscles are innervated by the median nerve.
The intrinsic muscles of the hand include the adductor pollicis, three hypothenar muscles, and the interossei. They are responsible for fine motor functions such as finger abduction and adduction, and flexion at the metacarpophalangeal and interphalangeal joints.
When the median nerve is injured, the intrinsic muscles it innervates may become paralyzed, affecting the patient's ability to make a fist and move their fingers and thumb.
Yes, in addition to the ulnar and median nerves, the radial nerve also innervates the intrinsic muscles of the hand, specifically the finger extensors and the thumb abductor.
