Upper Limb Muscle – Anatomy, Nerve Supply, Function

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 11 min read

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Article Summary

The Upper Limb Muscle comprises many muscles that are organized into anatomical compartments. These muscles act on the various joints of the hand, arm, and shoulder, maintaining tone, providing stability and allowing precise fluid movement. Axioappendicular groups of muscles arise from the axial skeleton to act upon the pectoral girdle. Scapulohumeral muscles originate from the scapula and insert into the proximal humerus. Included in this category...

Key Takeaways

This article explains Structure of Upper Limb Muscle in simple medical language.
This article explains Blood Supply of Upper Limb Muscle in simple medical language.
This article explains Nerves of Upper Limb Muscle in simple medical language.
This article explains Muscles of Upper Limb Muscle in simple medical language.

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Definition

The Upper Limb Muscle comprises many muscles that are organized into anatomical compartments. These muscles act on the various joints of the hand, arm, and shoulder, maintaining tone, providing stability and allowing precise fluid movement.

Axioappendicular groups of muscles arise from the axial skeleton to act upon the pectoral girdle. Scapulohumeral muscles originate from the scapula and insert into the proximal humerus. Included in this category are the rotator cuff muscles which provide stability to the glenohumeral joint. In the arm, the muscles of the anterior compartment are involved in flexion of the forearm, and the posterior comprises of the forearm extensors. Similarly, the anterior compartment of the forearm contains the flexors of the hand and posterior has extensors. The hand is divided into the thenar, the hypothenar, the adductor compartment, as well as the short muscles of the hand.[rx][rx][rx][rx]

Structure of Upper Limb Muscle

Shoulder and Upper limb muscles are specialized to perform functions of pressure and manipulation of objects. Skeletal muscle is formed by myofibers which contain millions of myofibrils, and each of them is formed by sarcomeres. Sarcomeres are the contractile unit, therefore skeletal muscle fibers are completely dedicated to generating force. Skeletal muscle also carries out multiple functions such as voluntary locomotion, the protection of internal organs, generation of heat, and assisting in postural behavior. [rx][rx]

The muscle mass relies on the balance between synthesis and degradation of proteins, the regulation of this process is sensitive to several factors such as nutritional status, hormone levels, physical activity, underlying diseases, injuries, among others.[rx]

Blood Supply of Upper Limb Muscle

The arterial supply to the muscles of the upper limb is primarily from the axillary artery (of subclavian artery) and its branches. The brachial artery supplies to the anterior compartment of the arm, and the profunda brachii supplies the posterior. In the arm, the radial artery supplies the lateral forearm and the ulnar is responsible for the medial aspect. Beyond the wrist, the radial and ulnar arteries form the superficial and deep palmar arterial arches. The deoxygenated blood drains into the cephalic vein and the basilic vein. Lymphatics of the right upper limb drain into the right lymphatic duct, and the left drains into the thoracic duct.[rx][rx][rx]

Nerves of Upper Limb Muscle

The innervation of the muscles of the upper limb is through branches of the brachial plexus which is composed of the ventral rami of C5 through T1 nerve roots.[rx][rx]

Muscles of Upper Limb Muscle

Anterior Axioappendicular Muscles (Thoracoappendicular Muscles)[12]

Pectoralis major

Function: flexion, adduction, medial rotation of the humerus.
Origin: clavicular head: medial clavicle anteriorly, sternocostal head: anterior sternum and costal cartilages of ribs 1 to 6 as well as external oblique aponeurosis
Insertion: lateral edge of intertrabecular groove of humerus
Innervation: medial pectoral nerve (C8, T1) lateral pectoral nerve (C5, C6, C7) of brachial plexus

Pectoralis minor

Function: Depression of shoulder, protraction of scapula
Origin: Third, fourth, fifth ribs close to their respective costal cartilages
Insertion: Coracoid process
Innervation: Medial pectoral nerve (C8, T1)

Subclavius

Function: Depression and stabilization of clavicle
Origin: First rib medially
Insertion: Middle of clavicle, inferiorly
Innervation: Nerve to subclavius (C5, C6)

Serratus anterior

Function: Protraction of scapula, rotation of scapula
Origin: Lateral first to the eighth rib
Insertion: anterior scapula, medially
Innervation: long thoracic nerve (C5, C6, C7)

Posterior Axioappendicular Muscles

Superficial layer

Latissimus dorsi

Function: Adduction, medial rotation, extension of humerus
Origin: Spinous processes of seventh to 12th thoracic vertebrae, iliac crest, thoracolumbar fascia, and inferior third and fourth rib
Insertion: Intertubercular groove of humerus
Innervation: Thoracodorsal nerve (C5,C6,C7)

Trapezius

Function: Elevation, depression, and retraction of the scapula, rotation of glenoid cavity
Origin: Superior nuchal line, nuchal ligament, occipital protuberance, spinous processes of C7- T12
Insertion: Spine of scapula, acromion, and lateral clavicle
Innervation: CN XI

Deep Layer

Levator scapulae

Function: Adduction, medial rotation, extension of humerus
Origin: Transverse processes of C1 through C4 vertebrae
Insertion: Scapula at its medial border
Innervation: Thoracodorsal nerve (C5, C6, C7)

Rhomboid major

Function: Retraction of scapula and depression of glenoid cavity
Origin: Spinous processes of T2 through T5 vertebrae
Insertion: Inferior aspect of medial scapula
Innervation: Dorsal scapular nerve (C4, C5)

Rhomboid minor

Function: Retraction of scapula and depression of glenoid cavity
Origin: Nuchal ligament as well as spines of C7 and T1 vertebrae
Insertion: Superior aspect of medial scapula
Innervation: Dorsal scapular nerve (C4, C5)

Scapulohumeral (Intrinsic Shoulder Muscles)

Deltoid

Function: Anterior part: flexion and medial rotation of arm, middle part: abduction of arm, posterior part: extension and lateral rotation of arm
Origin: Lateral clavicle, acromion and scapular spine
Insertion: Deltoid tuberosity
Innervation: Axillary nerve (C5, C6)

Teres major

Function: Adduction and medial rotation of arm
Origin: Posterior surface of scapula at its inferior angle
Insertion: Intertubercular groove on its medial aspect
Innervation: Lower scapular nerve (C5, C6)

Supraspinatus

Function: Initiation of arm abduction
Origin: Posterior scapula, superior to the scapular spine
Insertion: Superior aspect of the greater tubercle
Innervation: Suprascapular nerve (C5, C6)
Part of rotator cuff muscles

Infraspinatus

Function: Lateral rotation of arm
Origin: Posterior scapula, inferior to the scapular spine
Insertion: Greater tubercle of humerus, between supraspinatus and teres minor insertion
Innervation: Suprascapular nerve (C5, C6)
Part of rotator cuff muscles

Teres minor

Function: Lateral rotation of arm
Origin: Posterior surface of scapula at its inferior angle
Insertion: Inferior aspect of the greater tubercle
Innervation: Axillary nerve (C5, C6)
Part of rotator cuff muscles

Subscapularis

Function: Adduction and medial rotation of the arm
Origin: Anterior aspect of scapula
Insertion: Lesser tubercle of humerus
Innervation: Subscapular nerves (C5, C6, C7)
Part of rotator cuff muscles

*Rotator cuff muscles: supraspinatus, infraspinatus, teres minor, subscapularis

Muscles of Anterior Compartment of Arm (Flexors of Arm)

Biceps brachii

Function: Major flexion of forearm, supination of forearm, resists dislocation of shoulder
Origin: Short head originates from the coracoid process. The long head is from the supraglenoid tubercle of scapula
Insertion: Radial tuberosity and forearm fascia (as bicipital aponeurosis)
Innervation: Musculocutaneous nerve (C5, C6)

Brachialis

Function: Flexion of forearm
Origin: Distal anterior humerus
Insertion: Coronoid process and ulnar tuberosity
Innervation: musculocutaneous nerve (C5, C6, C7 small contribution)

Coracobrachialis

Function: Flexion and adduction of arm
Origin: Coracoid process
Insertion: Middle of the humerus, on its medial aspect
Innervation: Musculocutaneous nerve (C5, C6, C7)

Muscles of Posterior Compartment of Arm (Extensors of Arm)

Triceps brachii

Function: Major extensor of forearm, resists dislocation of shoulder
Origin: Lateral head: above the radial groove, medial head: below the radial groove, long head: infraglenoid tubercle of scapula
Insertion: Olecranon process of ulna and forearm fascia
Innervation: Radial nerve (C6,C7,C8)

Anconeus

Function: Extension of forearm, stabilization of elbow joint
Origin: Lateral epicondyle of humerus
Insertion: Olecranon process and posterior ulna
Innervation: Radial nerve (C7, C8, T1)

Muscles of Anterior Compartment of Forearm (Flexors of Forearm)

Superficial layer

Pronator teres

Function: Pronation of radio-ulnar joint
Origin: Coronoid process and medial epicondyle of humerus
Insertion: Lateral surface of the radius
Innervation: Median nerve (C6, C7)

Flexor carpi radialis

Function: Flexion and adduction at the wrist
Origin: Medial epicondyle of humerus
Insertion: Base of second metacarpal
Innervation: Median nerve (C6, C7)

Palmaris longus

Function: Flexion at the wrist, tensing of the palmaris aponeurosis
Origin: Medial epicondyle of humerus
Insertion: Flexor retinaculum
Innervation: Median nerve (C7, C8)

Flexor carpi ulnaris

Function: Flexion and adduction at the wrist
Origin: Medial epicondyle of humerus and olecranon
Insertion: Pisiform, hook of hamate and fifth metacarpal
Innervation: Median nerve (C7, C8)

Intermediate Layer

Flexor digitorum superficialis

Function: Flexion of the proximal interphalangeal joint of the second, third, fourth, and fifth finger. Also has a weaker flexion action on the metacarpophalangeal joints of the same fingers
Origin: Medial epicondyle, coronoid process, and anterior radius
Insertion: Second, third, fourth, and fifth middle phalanges
Innervation: Median nerve (C7, C8, T1)

Deep Layer

Flexor digitorum profundus

Function: Flexion of the distal interphalangeal joint of the second, third, fourth, and fifth finger
Origin: Medial and anterior surface of proximal ulna and interosseous membrane
Insertion: Second, third, fourth, and fifth distal phalanges
Innervation: Ulnar nerve (C8, T1) for the medial part, anterior interosseous nerve (C8,T1) for the lateral

Flexor pollicis longus

Function: Flexion of the interphalangeal joint of the thumb
Origin: Anterior aspect of radius as well as interosseous membrane
Insertion: Base of distal phalanx of thumb
Innervation: Anterior interosseous nerve (C7, C8)

Pronator quadratus

Function: Pronator of forearm
Origin: Anterior aspect of distal ulna
Insertion: Anterior aspect of distal radius
Innervation: Anterior interosseous nerve (C7, C8)

Brachioradialis

Function: Weak flexor of the forearm
Origin: Proximal supracondylar ridge on humerus
Insertion: Lateral surface of distal end of radius
Innervation: Radial nerve (C5, C6, C7)

Muscles of Posterior Compartment of Forearm

Superficial

Extensor carpi radialis longus

Function: Extension and abduction of the wrist
Origin: Proximal supracondylar ridge on humerus
Insertion: Dorsal base of second metacarpal
Innervation: Radial nerve (C6, C7)

Extensor carpi radialis brevis

Function: Extension and abduction of the wrist
Origin: Lateral epicondyle of humerus
Insertion: Dorsal base of third metacarpal
Innervation: Deep branch of the radial nerve (C7, C8)

Extensor digitorum

Function: Extension of the proximal interphalangeal joint of the second, third, fourth, and fifth finger. Also has a weaker extension action on the metacarpophalangeal joints of the same fingers
Origin: Lateral epicondyle of humerus
Insertion: Extensor expansions on dorsal aspect of second, third, fourth, and fifth middle and distal phalanges
Innervation: Posterior interosseous nerve (C7, C8)

Extensor digiti minimi

Function: Extension of the little finger at metacarpophalangeal joint and interphalangeal joint
Origin: Lateral epicondyle of humerus
Insertion: Extensor expansion on dorsal aspect of fifth phalanx
Innervation: Posterior interosseous nerve (C7, C8)

Extensor carpi ulnaris

Function: Extension and adduction of the wrist
Origin: Lateral epicondyle of humerus and posterior ulna
Insertion: Fifth metacarpal base
Innervation: Posterior interosseous nerve (C7, C8)

Deep Layer

Extensor indicis

Function: Extension of the index finger
Origin: Dorsal surface of distal ulna and interosseous membrane
Insertion: Extensor expansion of second finger
Innervation: Posterior interosseous nerve (C7, C8)

Supinator

Function: Supination of the forearm
Origin: Lateral epicondyle and supinator crest of ulna
Insertion: Lateral surface of radius
Innervation: Deep branch of radial nerve (C7, C8)

Abductor pollicus longus

Function: Abduction of the thumb by acting on the carpometacarpal joint and the metacarpophalangeal joint
Origin: Dorsal aspects of proximal radius, ulna, and interosseous membrane
Insertion: Base of first metacarpal
Innervation: Posterior interosseous nerve (C7, C8)

Extensor pollicus longus

Function: Extension of the thumb by acting on the carpometacarpal joint, the metacarpophalangeal joint, and the interphalangeal joint.
Origin: Dorsal aspects of middle ulna and interosseous membrane
Insertion: Distal phalanx of 1st finger
Innervation: Posterior interosseous nerve (C7, C8)

Extensor pollicus brevis

Function: Extension of the thumb by acting on the carpometacarpal joint and the metacarpophalangeal joint
Origin: Dorsal aspects of middle radius and interosseous membrane
Insertion: Distal phalanx of 1st finger
innervation: Posterior interosseous nerve (C7, C8)

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
Origin: Flexor retinaculum and hook of hamate
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

Lumbricals

Function: Flexion of the metacarpophalangeal joints with 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 second, third, fourth, and fifth finger
Innervation: Median nerve (C8, T1) for the lateral 2 lumbricals, deep branch of ulnar nerve (C8, T1) for the medial 2 lumbricals

Dorsal interossei

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 ulnar nerve (C8, T1)

Palmar interossei

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)

References

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

Write when the problem started and how it changed.
Bring old prescriptions, investigation reports, and current medicines.
Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

What is the most likely cause of my symptoms?
Which danger signs mean I should go to hospital quickly?
Which tests are necessary now, and which can wait?
How should I take medicines safely and what side effects should I watch for?
When should I come for follow-up?

Tests to discuss

Vital signs: temperature, pulse, blood pressure, oxygen saturation
Basic physical examination by a clinician
CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

Avoid heavy lifting, sudden bending, and prolonged bed rest.
Use comfortable posture and gentle movement as tolerated.
Discuss physiotherapy, X-ray, or MRI only when clinically needed.

OTC medicine safety

For mild back pain, pain-relief medicine may be discussed with a doctor or pharmacist.
Avoid repeated painkiller use if you have kidney disease, stomach ulcer, uncontrolled blood pressure, or are taking blood thinners.

Avoid these mistakes

Do not start antibiotics without a proper medical decision.
Do not use steroid tablets or injections casually for quick relief.
Do not delay emergency care because of home remedies.

Get urgent help if

Back pain with leg weakness, numbness around private area, loss of urine/stool control, fever, cancer history, or major injury needs urgent care.

Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Orthopedic / spine specialist, physical medicine doctor, or qualified clinician

Tests to discuss with doctor

Neurological examination for leg power, sensation, reflexes, and straight leg raise
X-ray only if injury, deformity, long-lasting pain, or doctor suspects bone problem
MRI discussion if severe nerve symptoms, weakness, bladder/bowel problem, or persistent symptoms

Questions to ask

What is the most likely cause of my symptoms?
Which warning signs mean I should go to emergency care?
Which tests are really needed now?
Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?
Is physiotherapy, posture correction, or activity modification needed?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Go to emergency care if you notice:

Severe or rapidly worsening symptoms
Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration

Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.

Step 1
Check danger signs first

If danger signs are present, seek emergency care and do not wait for online information.
Step 2
Record the symptom story

Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.
Step 3
Visit a qualified clinician

A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.
Step 4
Do only useful tests

Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.
Step 5
Follow up and return early if worse

If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips

Take a written symptom diary and all previous prescriptions/test reports.
Do not hide medicines already taken, even herbal or over-the-counter medicines.
Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

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When should I seek urgent care?

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References

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