The Hands Muscle – Anatomy, Nerve Supply, Functions
The Hands Muscle – Anatomy, Nerve Supply, Functions
The Hands Muscle have a very delicate and complex structure. This gives muscles and joints in the hand a great range of movement and precision. The different forces are also distributed in the best possible way. Thanks to this structure, you can do a wide range of things with your hands, such as grip objects tightly and lift heavyweights, as well as guide a fine thread through the tiny eye of a needle.
Hands are also quite vulnerable, though: Tendons, nerve fibers, blood vessels, and fairly thin bones are all positioned right under the skin and are only protected by a thin layer of muscle and fat. Only the palm is protected by a strong pad of tendons (aponeurosis), enabling a powerful grip. Our hands are put through quite a lot every day, and often come into contact with potentially harmful objects. As a result, hand injuries and problems due to wear and tear are very common.
The right and left hand are each controlled by the opposite side of the brain. Usually, one hand is preferred for carrying out fine and complex movements, so we often say people are either right- or left-handed.
Bones and Joints of The Hands
The human hand is made up of a total of 27 individual bones: 8 carpal bones, 5 metacarpal bones and 14 “finger bones” (also called phalanges) are connected by joints and ligaments. About one-quarter of all our body’s bones are found in our hands. The hand can be divided up into three different areas based on the joints:
Carpus (wrist bones)
Metacarpus
Fingers
The human hand has a total of 27 individual bones in it
Wrist
The wrist is made up of two parts of a joint that work as one functional unit. It allows us to flex (bend) or extend (stretch) our hands. We can also tilt our hands sideways, towards our little finger or thumb.
Carpus
The eight carpal bones are held together tightly by ligaments, and are more or less fixed in place. They are positioned in two rows of four carpal bones each. Together with the radius bone in the forearm, two of the carpal bones (the scaphoid bone and the lunate bone) form the lower part of the wrist joint, which is very important for hand movements. The ulna bone in the forearm is separated from the carpal bones by a cartilage disc. The other part of the joint is located between the two rows of carpal bones.
Metacarpus
After the second row of carpal bones comes the metacarpus. This middle part of the hand consists of five long metacarpal bones. You can feel them quite clearly on the back of your hand. One of the carpal bones and the long thumb bone come together to form the basal joint of the thumb. Known as the carpometacarpal joint, it enables the thumb to be particularly flexible.
Fingers
The freely movable part of our hand is made up of five digits (four fingers and one thumb). Each finger has three individual bones, and the thumb only has two. The fingers have three joints each, which can only be bent and stretched in one direction. The thumb is the only digit that can twist, thanks to the saddle-shaped carpometacarpal joint.
The Hands Muscle
There are over 30 muscles in the hand, working together in a highly complex way. Movements of the hand are mostly started by muscles in the forearm. Only the thin tendons of these muscles are found directly in the hand: the extensor tendons used for stretching the hand run through the back of the hand to the tips of the fingers, and the flexor (bending) tendons run through the palms to the fingers.
Intrinsic Muscles Of Hand
Thenar Muscles
Opponens pollicus
Function: Opposition of the thumb
Origin: Flexor retinaculum and tubercle of trapezium
Insertion: Lateral aspect of first metacarpal
Innervation: Recurrent branch of median nerve (C8, T1)
Abductor pollicus brevis
Function: Abduction of the thumb at the metacarpophalangeal joint
Origin: Flexor retinaculum and tubercle of scaphoid
Insertion: Lateral aspect of proximal phalanx of first finger
Innervation: Recurrent branch of median nerve (C8, T1)
Flexor pollicus brevis
Function: Flexion of the thumb at the metacarpophalangeal joint
Origin: Flexor retinaculum and tubercle of trapezium
Insertion: Lateral aspect of proximal phalanx of first finger
Innervation: Recurrent branch of median nerve (C8, T1)
Adductor Compartment
Adductor pollicus
Function: Adduction of the thumb
Origin: Second, third metacarpal, and capitate
Insertion: Proximal phalanx and extensor expansion of 1st finger
Innervation: Deep branch of ulnar nerve (C8, T1)
Hypothenar Muscles
Abductor digiti minimi
Function: Abduction of the little finger at the metacarpophalangeal joint
Origin: Pisiform
Insertion: Medial aspect of proximal phalanx of fifth finger
Innervation: Deep branch of ulnar nerve (C8, T1)
Flexor digiti minimi brevis
Function: Flexion of the little finger at the metacarpophalangeal joint
Insertion: Medial aspect of proximal phalanx of fifth finger
Innervation: Deep branch of ulnar nerve (C8, T1)
Opponens digiti minimi
Function: Opposition of the little finger
Origin: Flexor retinaculum and hook of hamate
Insertion: Medial aspect of fifth metacarpal
Innervation: Deep branch of ulnar nerve (C8, T1)
Short Muscles
There are short muscles between the individual metacarpal bones of the hand. They allow us to spread our fingers (abduction) and then pull them back together (adduction). They also help to bend and stretch the fingers.
Function: Adduction of the second, third, and fourth finger towards the axial line
Origin: Palmar surfaces of second, fourth, and fifth metacarpals
Insertion: Extensor expansions and proximal phalanges of the second, fourth, and fifth fingers
Innervation: Deep branch of ulnar nerve (C8, T1)
Hypothenar Muscles
Hypothenar Muscles
The hypothenar muscles are located at the base of the little finger. Their naming, function, and organization are similar to those of the thenar muscles.
Abductor digiti minimi
The most superficial of the hypothenar muscles.
Function: Abduction of the little finger at the metacarpophalangeal joint
Origin: Pisiform
Insertion: Medial aspect of proximal phalanx of the fifth finger
Innervation: Deep branch of the ulnar nerve (C8, T1)
Attachments: Originates from the wrist and attaches to the little finger.
Actions: Abducts the little finger.
Flexor digiti Minimi Brevis
Located laterally to the digiti minimi.
Function: Flexion of the little finger at the metacarpophalangeal joint
Origin: Flexor retinaculum and hook of hamate
Insertion: Medial aspect of proximal phalanx of the fifth finger
Innervation: Deep branch of the ulnar nerve (C8, T1)
Attachments: Originates from the wrist and attaches to the little finger.
Actions: Flexes little finger.
Opponents digit minimi
The opponent’s digit minimi is the deepest-lying of the hypothenar muscles.
Function: Opposition of the little finger
Origin: Flexor retinaculum and hook of hamate
Insertion: Medial aspect of the fifth metacarpal
Innervation: Deep branch of the ulnar nerve (C8, T1)
Attachments: Originates from the wrist and attaches to the little finger.
Actions: Rotates little finger towards the palm, producing opposition and improving grip.
Short Muscles
Lubricants
These are four lumbricals in the hand, each associated with an individual finger.
Attachments: Originates from a tendon of attached to the flexor digitorum profundus of the forearm, each attaching to an individual finger
Actions: Flexes and extends the fingers.
Function: Flexion of the metacarpophalangeal joints with the extension of the interphalangeal joints
Origin: Arise from tendons of flexor digitorum profundus. First 2 are unipennate, and the third and fourth are bipennate
Insertion: Extensor expansions of the second, third, fourth, and fifth finger
Innervation: Median nerve (C8, T1) for the lateral 2 lumbricals, deep branch of the ulnar nerve (C8, T1) for the medial 2 lumbricals
Interossei
The interossei muscles are located between the fingers; they can be split into two groups.
Dorsal interossei
Located superficially on the dorsal side of the hand, there are four dorsal interossei muscles.
Function: Abduction of the second, third, and fourth finger away from the axial line
Origin: Adjacent metacarpals
Insertion: Extensor expansions and proximal phalanges of the second, third, and fourth fingers
Innervation: Deep branch of the ulnar nerve (C8, T1)
Attachments: Originates from the base of the finger, each attaching after the first finger joint.
Actions: Abducts the fingers.
Palmar interossei
Located on the anterior side of the hand, there are three palmar interossei, with the index finger controlled by the extensor indices properties.
Function: Adduction of the second, third, and fourth finger towards the axial line
Origin: Palmar surfaces of second, fourth, and fifth metacarpals
Insertion: Extensor expansions and proximal phalanges of the second, fourth, and fifth fingers
Innervation: Deep branch of the ulnar nerve (C8, T1)
Attachments: Originates from the base of the finger, each attaching after the first finger joint.
Actions: Adducts the fingers.
Palmaris Brevis – The palmaris brevis is a small superficial muscle found in the palm.
Attachments: Originates from the fascia of the palm and attaches to the dermis.
Actions: Wrinkles the skin and deepens the curvature of the palm improving grip.
Blood Supply Of The Hands Muscle
The hand is supplied with blood through two main arteries: one on the same side as the thumb, and one on the same side as the little finger. These two arteries each curve around in an arch shape where the palm is, so that the hand is supplied with oxygen-rich blood through a double loop. These loops have branches leading off into the individual fingers. Each artery is accompanied by veins and nerves: In total, each finger is supplied by four bundles of nerves and blood vessels.
The suprascapular artery delivers blood to the supraspinatus muscle.
Blood supply of the deltoid
The posterior circumflex humeral artery and the deltoid branch of the thoracoacromial artery are the vascular sources for the deltoid.
Blood supply of the trapezius
The transverse cervical artery provides vascular supply to the trapezius.
Blood supply of the serratus anterior
The circumflex scapular artery is the blood supply to the serratus anterior.
The thenar eminence and the hypothenar eminence muscles
Two groups of more powerful muscles in the hand itself make up the thenar eminence (at the base of the thumb) and the hypothenar eminence (controlling the movement of the little finger). Among other things, the thenar muscles enable the thumb and the tips of the four fingers to touch each other (opposable thumb). A separate muscle (the adductor pollicis) is used to pull the thumb towards the palm. The hypothenar eminence muscles are mainly used for sticking out the little finger and pulling it inwards again, and for tightening the skin that covers the hypothenar eminence.
Lubricants
The lumbricals of the hand are four thin, worm-like muscles that help bend the metacarpophalangeal joints and extend the fingers.
Connective tissue and tendons
Some parts of the long flexor and extensor tendons of the forearm muscles are surrounded by protective layers called tendon sheaths. Tendon sheaths contain a fluid that acts as a lubricant. This allows the tendons to slide smoothly through the sheaths, without friction.
Muscle tendons, nerves and blood vessels running from the forearm to the hand pass through a tunnel-like passageway on the palm side of the wrist. Known as the carpal tunnel, this passageway is made up of strong connective tissue and carpal bones.
The carpal tunnel (seen from the palm side of the hand)
Function of the muscles: Power, touch and precision
Our hands can grasp and move objects in two different ways: with a power grip or precision grip. The object’s size, shape, weight, and ease of handling determine which of these two approaches is used. The power grip is better suited for large, heavy objects, and the precision grip is used for small, delicate objects.
Power grip
The power grip is used to do things like carry heavy bags or hold on to a handle. In the power grip, the object is held in the palm of the hand, and the long flexor tendons pull the fingers and the thumb so that they can tightly grasp the object. This grip is made possible by the four other fingers flexing (bending) and, most importantly, the ability of the thumb to be positioned opposite the fingers. With the hand in this position, larger objects such as a stone or a heavy bottle can be held and moved in a controlled way. The heavier the weight and the smoother the surface is, the more strength is needed to hold and move the object.
Precision grip
The precision grip is important for moving small and delicate objects, for example when writing, sewing or drawing. When using the precision grip, the thumb and the index (“pointer”) finger work like tweezers: The thumb is opposite one or more fingertips, allowing the hand to grip even very small objects – like pencils or delicate instruments – in a controlled way.
Location of the main nerves and blood vessels in the hand
Nerves of The Hands Muscle
The muscles and skin of the hand are supplied by three nerves:
the radial nerve (nervus radialis),
the median nerve (nervus medianus), and
the ulnar nerve (nervus ulnaris).
The ulnar nerve moves the muscles of the hypothenar eminence, the muscles between the bones of the metacarpus, the muscle that pulls the thumb inwards (adductor pollicis), and two of the lumbrical muscles between fingers. This nerve also picks up sensations from the area below the little finger and the side of the ring finger closest to it.
The median nerve is responsible for the movement of the thenar eminence muscles and the rest of the lumbricals. 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.
The radial nerve activates the finger extensors and the muscles in the wrist that are responsible for extending the hand. It also carries sensations from the skin on the back of the hand and the back of the thumb to the brain.
The sense of touch
The fingers, on one hand, are bent and stretched about 25 million times over the course of a lifetime. Our hands also have very sensitive “antennae” for receiving information from the environment: There are a total of 17,000 touch receptors and free nerve endings in the palm. These pick up sensations of pressure, movement and vibration, so it is with good reason that the sense of touch is often associated with the hand. The skin on our fingertips is especially sensitive to touch.
Pronator Teres – A muscle of the anterior compartment of the forearm that controls pronation.
Supinator – A muscle of the posterior compartment of the forearm that controls supination.
Pronator Quadraturs – A muscle of the anterior compartment of the forearm that controls pronation.
Brachioradialis – A muscle of the posterior compartment of the forearm that flexes the forearm.
Biceps Brachii – A muscle of the anterior compartment of the upper arm that flexes the forearm.
Triceps Brachii – A muscle of the posterior compartment of the upper arm that extends the forearm.
The extension (forearm away from the upper arm) – Produced by the triceps brachii and anconeus of the forearm.
Flexion (forearm towards the upper arm) – Produced by the brachialis, biceps brachii, and brachioradialis of the forearm.
Pronation (rotation of the forearm so the palm faces downwards) – Produced by the pronator quadratus and pronator teres of the forearm.
Supination(rotation of the forearm so the palm faces upwards) – Produced by the supinator of the forearm and biceps brachii.
Palmaris Longus – A long muscle originating near the elbow and passing through into the wrist, attaching to the base of the hand.
Flexor Digitorum Superficialis – A key muscle controlling wrist and finger flex.
Flexor Carpi Ulnaris – A long muscle originating near the elbow and passing through into the wrist, attaching to one of the carpal bones in the wrist.
Flexor Carpi Radialis – A long muscle originating near the elbow and passing through into the wrist, attaching to the base of the digits (fingers).
Flexor Digitorum Profundus – A long muscle originating near the elbow and passing through into the wrist, flexing the wrist and the most distant regions of the fingers.
Pronator Teres – A rectangular muscle that pronates the forearm.
Flexor Pollicis Longus – A long, deep muscle responsible for flexing the thumb.
Pronator quadratus – A square-shaped muscle located adjacent to the wrists
Key Terms
Pectoralis major – A large, fan-shaped muscle of the chest.
Rotator cuff –A set of four smaller muscles in the shoulder responsible for rotating the humerus (upper arm bone).
Trapezius – A large vertebrate skeletal muscle divided into an ascending, descending, and transverse portion, attaching the neck and central spine to the outer extremity of the scapula. It functions in scapular elevation, adduction, and depression.
Deltoid – The deltoid muscle, a triangular muscle on the human shoulder.
The extension (upper limb backward behind back) – Produced by the posterior deltoid, latissimus dorsi, and teres major.
Flexion (upper limb forwards past chest – Produced by the biceps brachii (both heads), pectoralis major, anterior deltoid, and coracobrachialis.
Abduction (upper limb away from the trunk, spreading arms wide) – Produced by the supraspinatus and deltoid. Past 90 degrees, the scapula needs to be rotated by the trapezius and serratus anterior to achieve abduction.
Adduction (upper limb towards the trunk, bringing arms down to side) – Produced by contraction of the pectoralis major, latissimus dorsi, and teres major.
Medial Rotation (rotation of arm inwards to cover abdomen) – Produced by contraction of the subscapularis, pectoralis major, latissimus dorsi, teres major, and anterior deltoid.
Lateral Rotation (rotation of arm outwards away from the abdomen) – Produced by contraction of the infraspinatus and teres minor.
The shoulder exhibits a wide range of movement, which makes it susceptible to dislocation and injury.
The trapezius muscles rotate the scapulae upward.
The rhomboid major and the rhomboid minor press the scapula against the thoracic wall, retracting the scapula towards the spine.
The deltoid is a complex muscle that forms the rounded edge of the shoulder and participates in many articulations of the shoulder joint.
The rotator cuff are the muscles that stabilize the movement of the shoulder.
The pectoralis minor and pectoralis major are large muscles of the chest that participate in many movements, including flexion of the humerus.
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