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The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. There are nine muscles that close the hand, and they attach at the fingers, thumb, hand, wrist, carpal tunnel, forearm, and elbow. The muscles that close the hand are generally located on the 'front' of the hand, while the muscles that open the hand are generally located on the 'back'. The muscles that close the hand include the opponens digiti minimi, opponens pollicis, flexor pollicis brevis, flexor digiti minimi, and flexor pollicis longus.
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What You'll Learn
Thenar muscles control the thumb
The thenar muscles are a group of three short muscles located at the base of the thumb. They are responsible for the thumb's fine movements, such as grabbing, gripping, and pinching. The thenar eminence is the mound formed at the base of the thumb by these intrinsic muscles. The word "thenar" comes from the Ancient Greek "θέναρ" (thenar), meaning "palm of the hand".
The three muscles that make up the thenar eminence are the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The abductor pollicis brevis is the most superficial of the three muscles and is responsible for abducting the thumb, or moving it away from the index finger. The flexor pollicis brevis lies next to the abductor and flexes the thumb, curling it up in the palm. The flexor pollicis brevis is also referred to as the deep head, and is supplied with nerves by the ulnar nerve.
The opponens pollicis is the largest of the three muscles and lies underneath the other two. It performs the important function of opposability, bringing the thumb against the fingers to grasp objects. The opponens pollicis is supplied with nerves by the ulnar nerve in about 20% of people. The median nerve innervates all the thenar muscles, and the nerves that reach them arise from the C8 and T1 roots, passing through the lower trunk of the brachial plexus and then through the medial cord of the plexus.
The adductor pollicis is another muscle that is important for thumb function, providing power for pinching and filling the first web space between the thumb and index finger. It is typically innervated by the ulnar nerve. The abductor pollicis longus is another muscle that passes through the first dorsal compartment of the wrist. Tendonitis is common in this area, known as De Quervain Syndrome or "Mommy thumb".
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Hypothenar muscles control the pinkie finger
The hypothenar muscles are a group of three muscles that control the motion of the little finger, or the pinkie finger. These muscles form a protrusion called the hypothenar eminence, which is located on the medial side of the palm, at the base of the pinkie finger. The hypothenar muscles are similar to the thenar muscles, which control the thumb, in both name and organisation.
The three hypothenar muscles are the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. The abductor digiti minimi is the most superficial of the three muscles. It originates from the pisiform and the tendon of the flexor carpi ulnaris, attaching to the base of the proximal phalanx of the little finger. The abductor digiti minimi abducts the little finger, allowing it to pull away from the ring finger.
The flexor digiti minimi brevis lies laterally to the abductor digiti minimi in the hand. It originates from the hook of hamate and adjacent flexor retinaculum, inserting into the base of the proximal phalanx of the little finger. The flexor digiti minimi flexes the metacarpophalangeal joint of the little finger, allowing it to bend at the MCP joint.
The opponens digiti minimi lies deep to the other two hypothenar muscles. It originates from the hook of hamate and associated flexor retinaculum, inserting into the medial margin of metacarpal V. The opponens digiti minimi rotates the metacarpal of the little finger towards the palm, allowing the hand to cup and the little finger to move towards the thumb.
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Interossei muscles help fingers move side-to-side
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. The interossei muscles are located between the metacarpal bones in the palm and help the fingers move side-to-side. 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, moving them away from each other. They also assist in flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal (IP) joints. The palmar interossei muscles, on the other hand, are strong adductors of the fingers, pulling them together. They also contribute to flexion and extension of the 2nd, 4th, and 5th fingers.
The interossei muscles work in conjunction with other muscle groups in the hand, such as the thenar and hypothenar muscles, to enable a range of finger movements and grips. The thenar muscles control the thumb, allowing it to move away from or towards the fingers for grasping objects. The hypothenar muscles, located on the outer edge of the palm near the pinkie finger, work similarly to the thenar muscles but on the opposite side of the hand.
The lumbrical muscles are yet another group of muscles that assist in finger movement. They are crucial in allowing the fingers to straighten and bend at the MCP joints. These muscles, along with the interossei muscles, enable the hand to perform two types of grips: power grip, which involves grip strength for tasks like lifting heavy objects, and precision grip, which involves fine finger movements for tasks like pinching small objects between the thumb and fingers.
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Lumbrical muscles help fingers flex and straighten
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. The lumbrical muscles are intrinsic muscles of the hand that help with finger flexion and extension. There are four lumbricals in each hand, and they are associated with each finger. They are crucial for finger movement, linking the extensor tendons to the flexor tendons.
The lumbricals attach proximally to the tendons of the flexor digitorum profundus, which arises from the ulna and interosseous membrane. Four tendons emerge from the flexor digitorum profundus, passing through the carpal tunnel and inserting into the tips of the index, middle, ring, and small fingers. The lumbricals then attach distally to the extensor expansions. This means that they attach to tendons, rather than bone, which makes their attachment points quite mobile.
The lumbricals flex the metacarpophalangeal (MCP) joints, which are at the knuckle, and extend the interphalangeal (IP) joints. This allows for complex movement of the hand, such as holding a pen, and contributes to the dexterity of the hand. The lumbricals can also help with finger flexion in the MCP joints.
The lumbricals are innervated by the median nerve and the deep branch of the ulnar nerve. The lateral two lumbricals (of the index and middle fingers) are innervated by the median nerve, while the medial two lumbricals (of the little and ring fingers) are innervated by the ulnar nerve. This is the typical innervation pattern, occurring in 60% of individuals. However, different innervation patterns have also been observed in a minority of cases.
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Flexors allow for the bending of fingers
The human hand is a complex network of bones, muscles, nerves, connective tissue, and blood vessels. The muscles in the hand work together to help us move our fingers and interact with the world around us.
There are 9 muscles that close the hand, which attach at the fingers, thumb, hand, wrist, carpal tunnel, forearm, and elbow. These muscles are generally located on the 'front' of the hand. The muscles that open the hand are generally located on the 'back' of the hand.
The flexors are responsible for the bending of the fingers. There are two long flexors in the fingers, located on the underside of the forearm. They insert by tendons to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, while the superficial flexor attaches to the middle phalanx. The thumb has one long flexor and a short flexor in the thenar muscle group. The thenar muscle group is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. The opponens pollicis, the largest of the thenar muscles, is essential for bringing the thumb away from the fingers, enabling us to grasp objects.
The lumbrical muscles also play a role in finger movement, linking the extensor tendons to the flexor tendons. They originate from a tendon of the flexor digitorum profundus and pass dorsally and laterally around each finger, inserting into the extensor hood. The lumbricals help with flexion at the MCP joints and extension at the interphalangeal (IP) joints of each digit. Additionally, the interossei muscles assist the lumbricals in flexion at the MCP joints.
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Frequently asked questions
There are 9 muscles that close the hand.
The muscles that close the hand are generally located on the 'front' of the hand, wrist, carpal tunnel, forearm, and elbow.
The names of the muscles that close the hand are: Opponens digiti minimi, Opponens pollicis, Flexor pollicis brevis, Flexor digiti minimi, Flexor pollicis longus, Palmaris brevis, Abductor pollicis brevis, Flexor digitorum superficialis, and Lumbricals.
The main function of the muscles that close the hand is to allow for grip and fine motor functions.
