M2 Attachments, Actions, Innervations of Axillary and Arm Muscles

Deltoid Spinal Segments

C5-6

Deltoid Attachments

from the clavicle, acromion & spine of the scapula to the deltoid tuberosity of the humerus

Deltoid Actions

flexion & medial rotation (anterior), abduction (primarily middle), extension & lateral rotation, horizontal extension (posterior) of humerus

Deltoid Innervations

axillary nerve

Pectoralis major Spinal Segments

clavicular head C5-7; sternocostal head C8-T1

Pectoralis major Attachments

from clavicle, costal cartilages, sternum & aponeurosis of the external oblique to the lateral lip of the intertubercular sulcus of the humerus

Pectoralis major Actions

humeral adduction, flexion & medial rotation (sternocostal portion assists with extension of the flexed arm)

Pectoralis major Innervations

lateral & medial pectoral nerves

Pectoralis minor Spinal Segments

C5-T1

Pectoralis minor Attachments

from outer surfaces of ribs 3-5 to the coracoid process

Pectoralis minor Actions

anterior tilt of scapula; assists with depression of the shoulder & forced inspiration

Pectoralis minor Innervations

medial & lateral pectoral nerves

Anconeus Spinal Segments

C7-8

Anconeus Attachments

from lateral epicondyle of humerus to lateral surface of the olecranon process

Anconeus Actions

extension of the elbow

Anconeus Innervations

radial nerve

Biceps brachii Spinal Segments

C5-6

Biceps brachii Attachments

from coracoid process (short head) & supraglenoid tubercle (long head) of the scapula to the radial tuberosity & the deep antebrachial fascia (through the bicipital aponeurosis)

Biceps brachii Actions

flexion of the shoulder & elbow, & supination of the forearm

Biceps brachii Innervations

musculocutaneous nerve

Brachialis Spinal Segments

C5-6

Brachialis Attachments

from the distal anterior shaft of the humerus & lateral & medial intermuscular septa to the coronoid process & ulnar tuberosity

Brachialis Actions

flexion of the elbow

Brachialis Innervation

musculocutaneous & small branch from radial nerve

Coracobrachialis Spinal Segments

C6-7

Coracobrachialis Attachments

from the coracoid process to the proximal medial shaft of the humerus

Coracobrachialis Actions

flexion & adduction of the shoulder

Coracobrachialis Innervation

musculocutaneous nerve

Triceps brachii Spinal Segments

C6-T1

Triceps brachii Attachments

from the infraglenoid tubercle of the scapula (long head), & proximal posterolateral (lateral head) & distal posteromedial (medial) shaft of the humerus to the olecranon process of the ulna

Triceps brachii Actions

extension of the shoulder (long head) & extension of the elbow (long, lateral & medial heads)

Triceps brachii Innervation

radial nerve