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The human hand is a complex structure made up of bones, muscles, nerves, connective tissue, and blood vessels. There are over 30 muscles in the hand and forearm that work together to allow for a wide range of movements. These muscles work with tendons and nerves to give your hand its strength and flexibility. The muscles in your hand can be categorised into groups, including the thenar muscles, which control your thumb, and the hypothenar muscles, which control the movement of your little finger. Squeezing and releasing exercises can help to strengthen the muscles in your hand and forearm.
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What You'll Learn
Thenar muscles control the thumb
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 34 muscles in each hand, which work together to help us move our hands and fingers.
The thenar muscle group, also known as the thenar eminence, is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. It is made up of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis.
The abductor pollicis brevis pulls the thumb away from the index finger. The flexor pollicis brevis bends the thumb toward the small finger. The opponens pollicis is the largest muscle in the thenar eminence. It performs one of the most important functions of the human hand: the ability to bring the thumb away from the fingers so that we can grasp objects. It helps pull the thumb away from the index finger, while rotating it, so that the tip of the thumb is opposite, or “opposes,” the tips of the other fingers. This motion is very important for tasks such as gripping and grasping objects.
The thenar muscles enable the thumb and the tips of the four fingers to touch each other (opposable thumb). The median nerve is responsible for the movement of the thenar eminence muscles. It is also responsible for the perception of skin sensations on the palm, thumb, index finger, and middle finger, as well as sensations on the side of the ring finger closest to the middle finger.
There are several conditions that can affect the thenar eminence, leading to a decrease in function or even atrophy of the muscles. For example, basal thumb arthritis is caused by the breakdown of cartilage around the lower thumb joint. While affecting the joints around the thenar eminence and not the muscles themselves, the condition can cause loss of motion or weakness of the thumb.
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Hypothenar muscles control the little finger
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 34 muscles in each hand, which work together to help you move your fingers and control objects.
The hypothenar muscle group is formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. These muscles are located in the hypothenar eminence, the muscular region at the base of the palm, specifically the area below the little finger. The hypothenar eminence is commonly associated with hypothenar hammer syndrome, a condition that occurs when a blood clot develops in the ulnar artery, resulting in localized pain and the possible formation of a mass.
The hypothenar muscles control the movement of the little finger. They allow the little finger to pull away from the ring finger and bend at the MCP joint. The abductor digiti minimi can spread the little finger away from the ring finger for greater control of grasp. The opponens digiti minimi allows us to cup our hands, bringing the little finger towards the thumb. The flexor digiti minimi, meanwhile, allows the little finger to bend at the MCP joint.
The hypothenar muscles are innervated by the ulnar nerve, which moves the muscles of the hypothenar eminence, the muscles between the bones of the metacarpus, and the muscle that pulls the thumb inwards (adductor pollicis). The ulnar nerve also picks up sensations from the area below the little finger and the side of the ring finger closest to it.
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Interossei muscles help fingers move side-to-side
The interossei muscles are intrinsic hand muscles that help fingers move side-to-side. They are situated between the metacarpal bones in the palm. There are four dorsal and three palmar interossei muscles. 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 first dorsal interosseous muscle is the largest and originates from the first and second hand bones. It forms the contour between the thumb and index finger when looking at the top of the hand. This muscle can be easily felt in the web between the thumb and index finger. The second dorsal interosseous originates from the medial aspect of the second metacarpal and the lateral aspect of the third metacarpal. This muscle inserts into the lateral base of the third proximal phalanx and its extensor hood.
The palmar interossei facilitate finger adduction, while the dorsal interossei enable abduction. Both muscle groups contribute to MCP joint flexion and interphalangeal joint extension. All interossei receive innervation from the deep branch of the ulnar nerve. Consequently, ulnar nerve injury may significantly impair intrinsic hand functions, particularly finger abduction and adduction.
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Lumbrical muscles help flex fingers
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, blood vessels, and parts of the lymphatic system. There are 34 muscles in each hand, which work together to help you move your hand and fingers.
Lumbrical muscles are a group of four intrinsic muscles in each hand that help flex the fingers. They are located at the base of the four non-thumb fingers and are thin, worm-like muscles that do not attach to bones. Instead, they attach proximally to the tendons of flexor digitorum profundus and distally to the extensor expansions. This makes their attachment points quite mobile, allowing for two different actions.
The first action is flexion at the metacarpophalangeal joints, which helps to bend the fingers. The second action is extension in both the proximal and distal interphalangeal joints, which helps to straighten the fingers. These combined movements play a role in the complex movement of the hand, such as holding a pen, and contribute to the hand's general dexterity.
The lumbrical muscles are supplied by the median nerve and the ulnar nerve. The median nerve innervates the first and second lumbricals, while the ulnar nerve innervates the third and fourth lumbricals. This is the typical innervation pattern, occurring in 60% of individuals. However, variations in innervation patterns, such as a 1:3 or 3:1 ratio of median to ulnar nerves, can also be found in a smaller percentage of the population.
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Flexor muscles help flex and curl fingers
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are 34 muscles in each hand, which work together to help us move our hands and fingers.
The flexor muscles are a group of muscles that help flex and curl the fingers. They are also known as the flexor digitorum profundus or flexor digitorum communis profundus. These muscles are located in the forearm and are considered extrinsic hand muscles as they act on the hand while being located in the forearm. The flexor digitorum profundus originates in the upper 3/4th of the anterior and medial surfaces of the ulna, interosseous membrane, and deep fascia of the forearm.
The flexor digitorum profundus fans out into four tendons, one for each of the second to fifth fingers, and attaches to the palmar base of the distal phalanx. These tendons are also known as flexor tendons and run through the palms to the fingers. The flexor digitorum profundus is the most powerful and bulky muscle of the forearm, providing the main gripping power of the hand.
The flexor digitorum profundus works in conjunction with the lumbrical muscles, which are thin, worm-like muscles that help bend the metacarpophalangeal joints and extend the fingers. The lumbricals originate from the flexor digitorum profundus tendons and insert into the dorsal extensor expansions of the proximal phalanges, aiding in full finger extension and flexion.
In addition to the flexor digitorum profundus, there are two other important flexor muscles: the flexor digitorum superficialis and the flexor pollicis longus. The flexor digitorum superficialis is an intermediate muscle that acts independently to flex the PIP joints. The flexor pollicis longus, as its name suggests, flexes the IP joint of the thumb. The simultaneous contraction of all three of these flexor muscles allows for activities such as gripping or holding objects.
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Frequently asked questions
The thenar muscle group, found at the base of the thumb, controls the thumb. It consists of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis.
The hypothenar muscle group, found on the outer edge of the palm, controls the little finger. It consists of three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi.
Interossei muscles are found between the metacarpal bones in the palm. There are four dorsal and three palmar interossei muscles. The dorsal interossei allow us to spread our fingers apart, while the palmar interossei pull our fingers together.
The carpal tunnel is a rounded space in the wrist that lets nine tendons, four ligaments, and one nerve pass through to reach the hand.
