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The human hand is a complex network of bones, muscles, nerves, tendons, and ligaments. There are 34 muscles in each hand, which work with tendons and ligaments to give the hand its dexterity and strength. These muscles can be categorised into extrinsic muscles, which are located in the forearm and control crude movements, and intrinsic muscles, which are located within the hand itself and are responsible for fine motor functions. The muscles of the hand are innervated by the radial, median, and ulnar nerves.
| Characteristics | Values |
|---|---|
| Number of muscles in each hand | 34 |
| Types of muscles | Intrinsic, Extrinsic |
| Intrinsic muscle location | Within the hand itself |
| Extrinsic muscle location | Anterior and posterior compartments of the forearm |
| Function of intrinsic muscles | Responsible for fine motor functions of the hand |
| Function of extrinsic muscles | Control crude movements and produce a forceful grip |
| Innervation | Radial, Median, Ulnar nerves |
| Example of intrinsic muscles | Thenar, Hypothenar, Interossei, Lumbrical |
| Function of Thenar muscles | Control thumb |
| Function of Hypothenar muscles | Control the area of the hand that's opposite the thumb |
| Function of Interossei muscles | Help fingers move side-to-side |
| Function of Lumbrical muscles | Help flex fingers |
| Types of grip | Power, Pinch |
| Function of extensors | Straighten out the digits |
| Function of flexors | Allow for the actual bending of the fingers |
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What You'll Learn
- Thenar muscles control the thumb and are located at its base
- Hypothenar muscles line the outside of the palm and control the area opposite the thumb
- Interossei muscles are between the metacarpal bones and help fingers move side-to-side
- Lumbrical muscles are at the base of the four non-thumb fingers, helping with finger flexion
- Forearm muscles contribute to the hand's range of motion
Thenar muscles control the thumb and are located at its base
The human hand is a complicated network of bones, muscles, nerves, tendons, ligaments, and blood vessels. There are 34 muscles in each hand, which healthcare providers categorise into groups.
One such group is the thenar muscles, which control the thumb and are located at its base. The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the intrinsic group of muscles of the thumb. The word thenar comes from the Ancient Greek 'θέναρ' ('thenar'), meaning 'palm of the hand'.
The thenar eminence is made up of three separate muscles that work to control the thumb's fine movements, including grabbing, gripping, and pinching objects. These muscles produce a bulge at the base of the thumb, which can be felt in the palm of the hand. The median nerve innervates all the thenar muscles.
The opponens pollicis is the largest of the thenar muscles and lies underneath the other two. Its function is very important to what makes human thumbs opposable. The opponens pollicis works to move the thumb away from the other fingers of the hand. During this motion, the thumb rotates so that it opposes, or is across from, the other four fingers of the hand. This motion is very important for tasks such as gripping and grasping objects.
The abductor pollicis brevis is located above the opponens pollicis along the outside of the thumb. Its function is to help move the thumb away from the index finger. The flexor pollicis brevis lies next to the abductor and will flex the thumb, curling it up in the palm.
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Hypothenar muscles line the outside of the palm and control the area opposite the thumb
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. There are 34 muscles in each hand, which can be categorised into groups. One such group is the hypothenar muscles, which line the outside of the palm and control the area opposite the thumb.
The hypothenar muscles are a group of three short muscles of the medial (ulnar) palmar compartment of the hand. They form a noticeable fleshy prominence on the medial side of the palm, called the hypothenar eminence. The hypothenar eminence is a muscular protrusion at the base of the little finger, on the outside of the pinkie finger.
The three hypothenar muscles are the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi muscles. The abductor digiti minimi is the most superficial of the hypothenar muscle group. It originates from the pisiform and the tendon of the flexor carpi ulnaris and attaches to the base of the proximal phalanx of the little finger. The flexor digiti minimi brevis lies laterally to the abductor digiti minimi. It originates from the hook of hamate and adjacent flexor retinaculum and inserts into the base of the proximal phalanx of the little finger. The opponens digiti minimi lies deep to the other hypothenar muscles. It originates from the hook of hamate and associated flexor retinaculum and inserts into the medial margin of metacarpal V.
The hypothenar muscles are innervated by the ulnar nerve, except for the palmaris brevis, which is supplied by the superficial branch of the ulnar nerve. The function of these muscles is to contribute to the variety of movements of the little finger, including flexion, abduction, lateral rotation, and opposition.
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Interossei muscles are between the metacarpal bones and help fingers move side-to-side
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. The hand and wrist work together to help us move our fingers and touch and control objects. The hand itself is made up of the palm, fingers, and thumb.
The interossei muscles are intrinsic hand muscles situated between the metacarpal bones in the palm. They help the fingers move side-to-side. The interossei muscles are divided into two groups: palmar interossei and dorsal interossei, each comprising four muscles. The palmar interossei facilitate finger adduction, while the dorsal interossei enable abduction.
The dorsal interossei muscles consist of four short muscles that attach to the adjacent sides of metacarpals 1-4. Their function is to abduct the digits 2-4, as well as to assist in flexion of these fingers at the metacarpophalangeal (MCP) joints and in extension at the interphalangeal (IP) joints. The palmar interossei act antagonistically to the dorsal interossei muscles, as the former brings the fingers towards the midline.
The interossei muscles also assist the lumbricals in flexion at the MCP joints and extension at the IP joints. The lumbrical muscles are at the base of the four non-thumb fingers and help with finger flexion.
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Lumbrical muscles are at the base of the four non-thumb fingers, helping with finger flexion
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. There are 34 muscles in each hand, which work together to help you move your fingers.
The flexor digitorum profundus arises from the ulna and interosseous membrane. Four tendons emerge from the muscle, passing through the carpal tunnel and inserting into the tips of the index, middle, ring, and small fingers. Its primary action is to bend these fingers, and it is able to do so independently due to its insertion past the last joint of the finger. The flexor digitorum profundus is also associated with several hand deformities and injuries, such as Quadrigia, Jersey finger, and ulnar claw hand deformity.
The main role of the lumbrical muscles is to allow the fingers to straighten, although they can also help bend the MCP joints, which are at the knuckle. The lateral two lumbricals, located at the index and middle fingers, are innervated by the median nerve, while the medial two lumbricals, located at the little and ring fingers, are innervated by the ulnar nerve.
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Forearm muscles contribute to the hand's range of motion
The forearm is the section of the upper limb from the elbow to the wrist, containing 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 divided into two compartments: the anterior flexor compartment and the posterior extensor compartment. These muscles are supported by the two forearm bones, the ulna and radius, which form a joint that rotates to let you turn your palm up or down.
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 you move your arms, hands, and fingers, and perform many tasks of daily life. For example, the pronator quadratus is a square-shaped muscle that lets you turn your forearm downward, while the extensor carpi radialis longus and extensor carpi radialis brevis extend your wrist and move your hand away from the direction of your thumb. The extensor digitorum splits into four tendons and connects to the finger joints, helping you to straighten or extend your fingers.
The extrinsic muscles, located in the anterior and posterior compartments of the forearm, control crude movements and produce a forceful grip. The intrinsic muscles, located within the hand itself, are responsible for the fine motor functions of the hand. These muscles inside your hand work with the extrinsic muscles near the outside of your hand and in your forearm to give your hand its strength and dexterity.
The thenar muscles are three short muscles located at the base of the thumb, responsible for the fine movements of the thumb. The hypothenar muscles line the outer edges of your palm on the outside of your pinkie finger and control the area of your hand opposite your thumb. The interossei muscles are between the metacarpal bones in your palm and help your fingers move side-to-side. The lumbrical muscles are at the base of your four non-thumb fingers and help you flex your fingers.
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Frequently asked questions
The muscles outside of the hand are known as extrinsic muscles. They are located in the forearm and control crude movements, producing a forceful grip.
The muscles inside the hand are known as intrinsic muscles. They are responsible for the fine motor functions of the hand.
Examples of extrinsic muscles include the flexor carpi ulnaris, which bends and deviates the wrist away from the thumb, and the extensor carpi radialis brevis and longus, which straighten and stabilise the wrist.
Examples of intrinsic muscles include the thenar muscles, which control the thumb, and the hypothenar muscles, which line the outer edges of the palm on the outside of the pinkie finger.
