Upper Extremity Muscles

Upper Extremity Muscles

Upper extremity muscles are composed of many long and short muscles which characterize structural features of the shoulder and elbow joints enabling it to perform delicate, precise movements within wide amplitude. We shall classify the muscles according to their actions on individual joints.

SHOULDER GIRDLE

  1. Those inserted on the humerus:
    Dorsal Group Ventral Group
    1. Supraspinatus
    2. Infraspinatus
    3. Teres minor
    4. Deltoid
    5. Subscapularis
    6. Teres major
    7. Latissimus dorsi
    1. Coracobrachialis
    2. Pectoralis minor (exception)
    3. Pectoralis major

     

  1. Those inserted on the shoulder girdle
Dorsal group Ventral Group
  1. Rhomboideus major
  2. Rhomboideus minor
  3. Levator scapulae
  4. Serratus anterior
  5. Head & neck muscles inserted on the shoulder girdle
  6. Trapezius
  7. sternocleidomastoid
  1. Subclavius
  2. Omohyoid

 

MUSCLES OF THE UPPER ARM

The upper arm is enclosed in a sheath of deep fascia which is thick at the back. Extensions of the deep fascia, which are called the medial & lateral intermusclur septae, divide the upper arm into anterior and posterior compartments.

Anterior Compartment (Flexors) Posterior Compartment (Extensors)
  1. Coracobrachialis
  2. Biceps brachii
  3. Brachialis
  1. Triceps brachii
  2. Anconeus

 

MUSCLES OF THE FOREARM

It is enclosed in a sheath of deep fascia which is attached to the posterior border of the ulna. This fascia sheath together with the interosseous membrane and fibrous intermuscular  septa divide the forearm into an anterior & posterior compartments.

ANTERIOR COMPARTMENT POSTERIOR COMPARTMENT
1.First Layer 1.Superficial
    1. Brachioradialis
    2. Pronator teres
    3. Flexor carpi radialis
    4. Palmaris longus
    5. Flexor carpi ulnaris
  1. Extensor carpi radialis longus
  2. Extensor carpi radialis brevis
  3. Extensor digitorum
  4. Extensor digiti minimi
  5. Extensor carpi ulnaris
2.Second Layer 2.Deep Layer
  • Flexor digitorum superficialis
  1. Supinator
  2. Abductor pollicis longus
  3. Extensor pollicis brevis
  4. Extensor pollicis longus
  5. Extensor indicis
3.Third Layer
  1. Flexor digitorum profundus
  2. Flexor pollicis longus

MUSCLES OF THE HAND

Here there are three groups of muscles:

  1. Thenar Eminence  :  
    Abductor pollicis brevis
    Opponens pollicis
    Flexor pollicis brevis
    Adductor pollicis
  2. Hypothenar Muscles : 
    Palmaris brevis
    Abductor digiti minimi brevis
    Opponens digiti minimi
    Flexor digiti minimi brevis
  3. Middle Group  :
    Llumbrical
    Dorsal interossei

 

Muscle Origin Insertion Action Innervation

Those inserted on The Humerus
(Dorsal Group)

  1. Supraspinatus
Supraspinous fossa of scapula & supraspinous fascia Greater tubercle of humerus & capsule of shoulder joint Abduction of the arm; stretching of the articular capsule Suprascapular nerve
  1. Infraspinatus
Infraspinous fossa of scapula & infraspinous fascia Greater tubercle of humerus Lateral rotation of the arm Suprascapular nerve
  1. Teres minor
Lateral margin of scapula & infraspinous fascia Greater tubercle of humerus Lateral rotation of the arm Axillary nerve
  1. Deltoid
Acromial end of clavicle, acromion & scapular spine Deltoid tuberosity of humerus Whole muscle abducts the arm to horizontal level: the clavicular part flexes the arm; spinous part extends the arm Axillary nerve
  1. Subscapularis
Subscapular fossa & lateral margin of scapula Lesser tubercle of the humerus & its crest Pronates the arm & adducts it to the body Subscapular nerve
  1. Teres major
Inferior angle of scapula and infraspinous fascia Crest of the lesser tubercle of humerus Medial rotation & adduction of the arm Subscapular nerve
  1. Latissimus dorsi
Spinous process of lower T6 and all lumbar vertebra, iliac crest, medial sacral crest & 3-4 lower ribs Cresit of the lesser tubercle of humerus Adduction of arm, lowers a raised arm as well as pronation & extension in the shoulder. Thoracodorsal nerve

(Ventral Group)

  1. Coracobrachialis
Coracoid process of scapula Humerus, below the crest of the lesser tubercle Flexion & adduction in the shoulder joint Musculocuteneous nerve
  1. Pectoralis minor (exception)
Outer surface of ribs 3,4 & 5 near their anterior ends. Medial border & upper surface of the coracoid process of the scapula Draws shoulder forward & downwards. It depresses the shoulder. Medial pectoral nerve (C8 & T1) by piercing the muscle
Lateral pectoral nerve (C5,6,7) that communicates with pectoral nerve.
  1. Pectoralis major
Clavicular head: from front of the medial half or 2/3 of the anterior surface of the clavicle
Sternocostal head: infront of manubrium sterni & body of sternum close to the midline.
Abdominal head: from aponeurosis of the external oblique muscle of the abdomen.
Lateral lip of the intertubercular sulcus of the humerus by a bilaminar tendon.
Fibres of clavicular head are attached infront & distal to the sternocostal part.
A powerful adductor and medial rotator of the humerus
Main climbing muscles and pulls the body up to the flexed arm.
Acts as an accessory respiratory muscle
Lateral pectoral nerve (C5,6,7)
Medial pectoral nerve (C8,Th1)

Those inserted on The Shoulder Girdle
(Dorsal Group)

  1. Rhomboideus major
Spinous process of Th2-Th5 vertebrae Medial margin of the scapula below the scapular spine Move the scapula towards the vertebral column, raising it up Dorsal scapular nerve
  1. Rhomboideus minor
Spinous process of C7 & Th1 vertebrae Medial margin of scapula above the scapular line. Move the scapula towards the vertebral column, raising it up Dorsal scapular nerve
  1. Levator scapulae
Tendon fascicles from the transverse processes of 3-4 upper cervical vertebrae Upper part of the medial margin of the scapula. Its upper 1/3 is covered by sternocleidomastoid (SCM) & lower 1/3 by trapezius Lifts the scapula bringing it closer to the spine. Dorsal scapular nerve
  1. Serratus anterior
Spinous processes of C6, C7, Th1 & Th2 vertebrae Back surfaces of ribs 1-5 lateral to their angles Lifts the ribs Intercostal nerves

Ventral Group

  1. Subclavius
Cartilage of rib 1 Acromial end of clavicle Pulls the clavicle medially & downwards Subclavian nerve
  1. Omohyoid
Superior margin of scapula. Hyoid bone Pulls hyoid bone downwards & stretches the cervical fascia. Cervical ansa

Head & Neck Muscles Inserted on The Shoulder Girdle

  1. Trapezius
External occipital protuberance, mediall part of the upper nuchal line, he nuchal lig. and the spinous processes of the C7 & all thoracis vertebrae. Lateral third of the clavicle, the acromion and the scapular spine By simultaneous contraction, it moves the scapula to the vertebral column. Accessory nerve & branches of cervical plexus
  1. sternocleidomastoid
Anterior surface of manubrium sterni & medial end of clavicle. Mastoid process of the temporal bone During bilateral contraction it bends the head back.
Accessory muscle in respiration
Accessory nerve

MUSCLES OF THE ARM
Anterior Compartment (Flexors)

  1. Coracobrachialis
Coracoid process of scapula Humerus, below the crest of the lesser tubercle Flexion and adduction in  the shoulder joint Musculocuteneous nerve
  1. Biceps brachii
Long head: superglenoid tubercle of scapula
Short head: coracoid process
Radial tuberosity & bicipital aponeurosis Flexion and supination of forearm in the elbow joint; flexion in the shoulder joint Musculocuteneous nerve
  1. Brachialis
Humerus, distal of the deltoid tuberosity Tuberosity of ulna Flexion of forearm Musculocuteneous nerve

Posterior Compartment (Extensors)

  1. Triceps brachii
Long head: infraglenoid tubercle
Medial & lateral heads: posterior surface of the body of humerus
Olecranon process of ulna Extension of forearm in elbow joint; long head extends and adducts the arm Radial nerve
  1. Anconeus
Lateral epicondyle of humerus Olecranon & posterior surface of ulna Extension of forearm in the elbow Radial nerve

FOREARM
(Anterior Compartment)

First layer

  1. Brachioradialis
Lateral supracondylar crest of humerus and lateral intermuscular septum of arm Radius, above the styloid process Flexion of arm and setting it in a middle position between supination & pronation Radial nerve
  1. Pronator teres
Media epicondyle of humerus and coronoid process of ulna Lateral surface of radius Pronation & flexion of the forearm Median nerve
  1. Flexor carpi radialis
Medial epicondyle of humerus, medial intermuscular septum of arm and antebrachial fascia Palmar surface of bases of the II-III metatarsal bones Flexion of the wrist, abduction of the hand, and flexion of the forearm Median nerve
  1. Palmaris longus
Medial epicondyle of humerus, medial intermuscular septum of arm Palmar aponeurosis Stretches the palmar aponeurosis and flexes the forearm and hand Median nerve
  1. Flexor carpi ulnaris
Medial epicondyle of humerus, medial intermuscular septum of arm, olecranon and antebrachial fascia Pisiform and hamate bones and base of fifth metacarpal Flexion of the wrist, abduction of the hand and flexion of the forearm Ulnar nerve
Second layer

  1. Flexor digitorum superficialis
Medial epicondyle of humerus, coronoid process of ulna and antebrachial fascia Four tendons insert on palmar surface of middle phalanges of II-V fingers. Near the shafts of proximal phalanges each tendon splits into two parts, beneath which pass the tendons of the deep flexor Flexion of the middle phalanges of II-V fingers, flexion of the hand and forearm Median nerve
Third layer

  1. Flexor digitorum profundus
Anterior surface of ulan, interosseous membrane of the forearm Four tendons insert on the distal phalanges of fingers II-V Flexion of distal phalanges of fingers II-V and flexion of the hand Median & ulnar nerves
  1. Flexor pollicis longus
Anterior surface of radius intersseous membrane of the forearm Palmar surface of distal phalanx of the first finger Flexion of the thumb and hand Median nerve
Fourth layer

  1. Pronator quadratus
Anterior margin and medial anterior surface of ulna Anterior surface of radius (its lower quarter) Pronation of the forearm and hand Median nerve

 

 

POSTERIOR COMPARTMENT

Superficial

  1. Extensor carpi radialis longus
Lateral epicondyle of humerus, lateral intermuscular septum of arm Dorsal surface of base of the 2nd metacarpal bone Extension and abduction of the hand; flexion of the forearm Radial nerve
  1. Extensor carpi radialis brevis
Lateral epicondyle of humerus and antebrachial fascia Dorsal surface of base of the third metacarpal bone Extension and abduction of the hand Radial nerve
  1. Extensor digitorum
Lateral epicondyle of humerus and antebrachial fascia Four tendons insert on dorsal surfaces of middle and distal phalanges (dorsal aponeurosis of fingers) Extension of fingers II-V and extension of the hand Radial nerve
  1. Extensor digiti minimi
Lateral epicondyle of humerus and antebrachial fascia Dorsal surface of middle and distal phalanges of the little finger (into its dorsal aponeurosis) Extension of the little finger Radial nerve
  1. Extensor carpi ulnaris
Lateral epicondyle of humerus and antebrachial fascia Dorsal surface of the base of the 5th metacarpal Extension and abduction of the hand Radial nerve

 

Deep Layer

  1. Supinator
Lateral epicondyle of humerus, ulna Proximal third of the lateral surface of radius Supination of the forearm Radial nerve
  1. Abductor pollicis longus
Dorsal surface of radius and ulna, and interosseous membrane of forearm Dorsal surface of the base of the first metacarpal Abduction of the thumb and hand Radial nerve
  1. Extensor pollicis brevis
Dorsal surface of radius, interosseous membrane of forearm Dorsal surface of the base of the proximal phalanx of thumb Extension of the proximal phalanx of the thumb Radial nerve
  1. Extensor pollicis longus
Dorsal surface of ulna, interosseous membrane of forearm Dorsal surface of the base of the distal phalanx of the thumb Extends the thumb Radial nerve
  1. Extensor indicis
Dorsal surface of ulna, interosseous membrane of forearm Dorsal surface (aponeurosis) of the proximal phalanx of index finger Extension of the index finger Radial nerve

MUSCLES OF THE HAND
Muscles of The Thenar

  1. Abductor pollicis brevis
Scaphoid and trapezium bones, flexor retinaculum of the hand Lateral border of the base of the proximal phalanx of the thumb Abduction of the thumb Median nerve
  1. Flexor pollicis brevis
Trapezium and trapezoid bones, flexor retinaculum of the hand, second metacarpal bone Anterior surface of the base of the proximal phalanx of the thumb Flexion of the thumb Median and ulnar nerves
  1. Opponens pollicis
Trapezium bone, flexor retinaculum of the hand Lateral border and anterior surface of the first metacarpal  Opposition of the thumb to the little finger Median nerve
  1. Adductor pollicis
Capitate bone, bases and anterior surfaces of II and III metacarpals Base of the proximal phalanx of the thumb Adduction of the thumb Ulnar nerve

Muscle of The Hypothenar

  1. Palmaris brevis
Flexor retinaculum of the hand Skin of the medial border o the hand Wrinkles skin of the hypothenar region Ulnar nerve
  1. Abductor digiti minimi
Flexor retinaculum of the hand and pisiform bone Medial border of the base of the proximal phalanx of the little finger Abducts the little finger Ulnar nerve
  1. Flexor digiti minimi brevis
Hook of the hamate bone and flexor retinaculum of the hand Palmar surface of the proximal phalanx of the little finger Flexion of the little finger Ulnar nerve
  1. Opponens digiti mnini
Hook of the hamate bone and flexor retinaculum of the hand Medial border and anterior surface of the fifth metacarpal bone Opposition of little finger to thumb Hook of the hamate bone and flexor retinaculum of the hand
Middle group of muscles
  1. Lumbricals
Tendons of the deep flexors of fingers Dorsal surface (aponeurosis) of the proximal phalanges of II-V fingers Flexion of the proximal phalanges; extension of the middle and distal phalanges First and second lumbracals – median nerve; third and fourth – ulnar nerve
  1. Palmar interossei
Medial border of II and lateral border of IV and V metacarpal bones Dorsal surface (aponeurosis) of proximal phalanges of fingers II, IV, V Adduction of fingers II, IV and V to the third finger Ulnar nerve
  1. Dorsal interossei
Adjacent surfaces of I-V metacarpals Dorsal surfaces (aponeurosis) of proximal phalanges of II-IV fingers Abduction of fingers II, IV and V from the third finger. Ulnar nerve