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The intrinsic muscles of the hand are located within the hand itself and are responsible for fine motor functions. They are innervated by the radial, median, and ulnar nerves. The median nerve, for example, innervates the flexors of the wrist and digits, as well as the abductors and opponens of the thumb. The ulnar nerve innervates the remaining intrinsic muscles of the hand, such as the hypothenar eminence muscles, which include the abductor, flexor, opponens digiti minimi, and palmaris brevis.
| Characteristics | Values |
|---|---|
| Location | Within the hand itself |
| Function | Responsible for the fine motor functions of the hand |
| Innervation | Radial, median, and ulnar nerves |
| Anatomy | Thenar, hypothenar, dorsal interossei, palmar interossei, and lumbricals |
| Attachments | Vary depending on the specific muscle, but can include origins from the metacarpal shafts, hook of hamate, flexor retinaculum, and tubercle of the trapezium |
| Actions | Flexion, extension, abduction, adduction, opposition, and grasping |
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What You'll Learn
- The hand has four lumbricals, each associated with a finger, that are innervated by the median or ulnar nerve
- The thenar eminence is a group of three short muscles located at the base of the thumb, controlling its fine movements
- The hypothenar eminence is a muscular protrusion on the medial side of the palm, at the base of the little finger
- The median nerve innervates the flexors of the wrist and digits, and the thumb's abductors and opponens
- The ulnar nerve innervates the remaining intrinsic muscles of the hand
The hand has four lumbricals, each associated with a finger, that are innervated by the median or ulnar nerve
The ulnar nerve is formed from the C8 and C1 nerve roots and is very close to the skin at the elbow. The ulnar nerve can also be compressed when it crosses the elbow, causing numbness and tingling in the small and ring fingers and weakness in the hand, known as cubital tunnel syndrome. The medial two lumbricals, associated with the little and ring fingers, are innervated by the ulnar nerve. The ulnar nerve powers almost all the small muscles in the hand, including the hypothenar muscles, the lumbricals to the ring and small fingers, and the palmar and dorsal interossei muscles.
The intrinsic muscles are located within the hand itself and are responsible for the hand's fine motor functions. The thenar muscles are three short muscles located at the base of the thumb and are responsible for the thumb's fine movements. The median nerve innervates all the thenar muscles. The hypothenar muscles form the hypothenar eminence, a muscular protrusion on the medial side of the palm, at the base of the little finger. The ulnar nerve innervates the hypothenar eminence muscles.
The four lumbricals in the hand are crucial to finger movement, linking the extensor tendons to the flexor tendons. Denervation of these muscles is the basis for the ulnar claw and hand of benediction. Each lumbrical originates from a tendon of the flexor digitorum profundus, passing dorsally and laterally around each finger and inserting into the extensor hood.
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The thenar eminence is a group of three short muscles located at the base of the thumb, controlling its fine movements
The human hand is a complex structure, with intrinsic muscles located within the hand itself, controlling its fine motor functions. The thenar eminence is a group of three short muscles located at the base of the thumb, controlling its fine movements. These muscles produce a bulge at the base of the thumb, which is known as the thenar eminence. The three muscles are the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis.
The abductor pollicis brevis forms the anterolateral aspect of the thenar eminence, overlying the opponens pollicis. It originates from the tubercles of the scaphoid and trapezium and from the associated flexor retinaculum. It attaches to the lateral side of the proximal phalanx of the thumb. The function of this muscle is to abduct the thumb, moving it away from the index finger.
The flexor pollicis brevis is the most medial of the thenar muscles. It has two muscle heads, superficial and deep, which are separated by the tendon of the flexor pollicis longus. The superficial head originates from the flexor retinaculum and the tubercle of the trapezium bone, while the deep head originates from the trapezoid and capitate bones. The heads run side by side in a lateral direction to insert into the base of the proximal phalanx. The flexor pollicis brevis flexes the metacarpophalangeal joint of the thumb, allowing movement towards the other fingers.
The opponens pollicis is the largest of the thenar muscles and lies underneath the other two. It is a short muscle located deep to the abductor pollicis brevis. The opponens pollicis originates from the tubercle of the trapezium bone and the flexor retinaculum, with muscle fibres running distally to insert onto the lateral aspect of the first metacarpal bone. This muscle is responsible for moving the thumb away from the other fingers, allowing it to be opposable. This movement is crucial for tasks such as gripping and grasping objects, as it enables the thumb to oppose or be across from the other four fingers.
The thenar eminence muscles are innervated by the median nerve, except for the deep head of the flexor pollicis brevis, which, along with the adductor pollicis, is innervated by the ulnar nerve. The median nerve originates from the brachial plexus, running along the inside of the arm and supplying nerves to the muscles of the forearm, wrist, and hand. The ulnar nerve also originates from the brachial plexus, moving down the arm and supplying nerves to the muscles of the hand.
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The hypothenar eminence is a muscular protrusion on the medial side of the palm, at the base of the little finger
The hypothenar eminence is a muscular protrusion located on the medial side of the palm, at the base of the little finger. It is formed by the hypothenar muscles, which are similar to the thenar muscles in both name and organisation. The thenar muscles, on the other hand, are located at the base of the thumb and are responsible for the thumb's fine movements.
The hypothenar eminence is made up of three muscles: the abductor digiti quinti, the flexor digiti quinti brevis, and the opponens digiti quinti. These muscles originate primarily from the pisiform bone and the pisohamate ligament and insert into the joint capsule of the fifth metacarpophalangeal joint. The ulnar nerve innervates the muscles of the hypothenar eminence.
The function of the hypothenar eminence is to allow for a similar but less pronounced rotation of the fifth metacarpal, which is the bone of the little finger, towards the palm. This movement is known as opposition and is crucial for the hand's fine motor functions. The opponens digit minimi, one of the hypothenar muscles, is responsible for this rotation. It originates from the hook of hamate and associated flexor retinaculum and inserts into the medial margin of metacarpal V.
The hypothenar eminence is also associated with a condition known as hypothenar hammer syndrome. This condition occurs in individuals who use this region as a hammer and develop a blood clot in the ulnar artery, resulting in localized pain and the possible formation of a mass. The diagnosis of hypothenar hammer syndrome can be confirmed by performing an Allen's test, which assesses the refill of blood to the ulnar digits.
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The median nerve innervates the flexors of the wrist and digits, and the thumb's abductors and opponens
The muscles of the hand are innervated by the radial, median, and ulnar nerves. The median nerve is responsible for the hand's motor functions, such as enabling movement and providing sensation to the forearm, wrist, and hand. It also helps us perform both coarse and fine movements of the upper limb.
The median nerve innervates the flexors of the wrist and digits, and the thumbs' abductors and opponens. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), enabling the thumb to move in opposition, making grasping possible.
The median nerve is also responsible for touch, pain, and temperature sensations to the bottom (palm) side of the thumb, index, and middle fingers, and part of the ring finger. It also provides sensation to certain areas of the skin of the hand.
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. After giving off these branches, the median nerve enters the hand via the carpal tunnel, where it divides into two branches: the recurrent branch and the palmar digital nerves.
The recurrent branch innervates the thenar muscles, which are responsible for the fine movements of the thumb. The opponens pollicis is the largest of the thenar muscles and lies underneath the other two. It originates from the tubercle of the trapezium and the associated flexor retinaculum and inserts onto the lateral margin of the first metacarpal. The palmar digital nerves innervate the palmar surface and fingertips of the lateral three and a half digits, also providing branches to the lateral two lumbricals.
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The ulnar nerve innervates the remaining intrinsic muscles of the hand
The muscles of the hand are innervated by the radial, median, and ulnar nerves. The radial nerve innervates the muscles that extend at the wrist and metacarpophalangeal joints, such as the finger extensors and the thumb abductor. The median nerve, meanwhile, innervates the flexors of the wrist and digits, as well as the abductors and opponens of the thumb.
The ulnar nerve, a major peripheral nerve of the upper limb, is responsible for innervating the remaining intrinsic muscles of the hand. It courses through the axilla, arm, and forearm into the hand, providing both motor and sensory innervation to various muscles and skin areas. Ulnar nerve injuries are common and can result in considerable impairment of hand function, with symptoms such as tingling, numbness, and the "claw hand" deformity.
The ulnar nerve innervates the majority of the intrinsic hand muscles, including the hypothenar muscles (abductor, flexor, and opponens digiti minimi muscles), the interossei (3 palmar and 4 dorsal), the medial two lumbricals, the deep head of flexor pollicis brevis, and the adductor pollicis. The palmaris brevis is an exception, innervated by the superficial branch of the ulnar nerve, while the lateral two lumbricals and the thenar eminence are innervated by the median nerve.
The ulnar nerve also gives rise to two muscular branches in the forearm: one supplying the flexor carpi ulnaris and the other supplying the ulnar (medial) part of the flexor digitorum profundus. The flexor digitorum profundus, specifically its medial half, is responsible for flexing the ring and little fingers at the distal interphalangeal joint. The lateral half of the flexor digitorum profundus muscle and the remaining muscles of the anterior compartment of the forearm are supplied by the median nerve.
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Frequently asked questions
Intrinsic muscles are located within the hand itself and are responsible for the hand's fine motor functions.
Some examples of intrinsic hand muscles include the thenar muscles, the hypothenar muscles, and the lumbricals.
The thenar muscles are responsible for the fine movements of the thumb. They include the opponens pollicis, the abductor brevis muscle, and the flexor pollicis brevis.
The hypothenar muscles form a muscular protrusion on the medial side of the palm, at the base of the little finger. They include the abductor, flexor, opponens digiti minimi, and palmaris brevis.
There are four lumbricals in the hand, each associated with a finger. They are crucial for finger movement, linking the extensor tendons to the flexor tendons.
