Upper Limb Musculature: Scapula, Humerus, Brachium, and Antebrachium

Comprehensive practice flashcards covering the origins, insertions, innervations, actions, and visual identification of muscles that move the scapula, humerus, brachium, and antebrachium.

Trapezius muscle: Attachments, innervation, and primary actions

Origin: Occipital bone, spines of C1-C7 and T1-T12. Insertion: Acromion, spine of scapula, lateral 1/3 of clavicle. Innervation: CN XI (Spinal Accessory Nerve). Actions: Extends neck; elevates, depresses, and retracts scapula; assists superior scapular rotation.

Serratus anterior: Attachments, innervation, and functional actions

Origin: Ribs 1-9. Insertion: Medial border of scapula. Innervation: Long thoracic nerve. Actions: Protracts and stabilizes scapula against thoracic wall; produces superior scapular rotation with the trapezius.

Levator scapulae: Attachments, innervation, and primary actions

Origin: Transverse processes of C1-C4. Insertion: Superior angle and medial border of scapula. Innervation: Dorsal scapular nerve. Actions: Elevates scapula; assists inferior scapular rotation with pectoralis minor and rhomboids.

Rhomboid major and minor: Attachments, innervation, and scapular functions

Origin: Spinous processes of C7-T1 (minor) and T2-T5 (major). Insertion: Medial border of scapula. Innervation: Dorsal scapular nerve. Actions: Retract, elevate, and stabilize scapula; produce inferior scapular rotation.

Pectoralis minor: Attachments, innervation, and scapular functions

Origin: Ribs 3-5. Insertion: Coracoid process of scapula. Innervation: Medial and lateral pectoral nerves. Actions: Depresses, protracts, and stabilizes scapula; produces inferior scapular rotation.

Scapular superior rotation: Sequential muscle activation sequence

1. Upper part of trapezius
2. Inferior part of trapezius
3. Serratus anterior

Scapular inferior rotation: Sequential muscle activation sequence

1. Rhomboids (major and minor)
2. Levator scapulae
3. Pectoralis minor

Rotator cuff: Functional mechanics of simultaneous vs. sequential contraction

Simultaneous contraction stabilizes the humeral head in the glenoid cavity to prevent dislocation. Sequential contraction drives dynamic rotation of the humerus.

Supraspinatus: Attachments, innervation, and shoulder action

Origin: Supraspinous fossa of scapula. Insertion: Greater tubercle of humerus. Innervation: Suprascapular nerve. Action: Initiates humerus abduction.

Infraspinatus and teres minor: Innervation comparison and shared action

Shared action: Lateral (external) rotation of the humerus (both insert on greater tubercle). Innervations: Infraspinatus is innervated by the suprascapular nerve; teres minor is innervated by the axillary nerve.

Subscapularis: Attachments, innervation, and humeral movement

Origin: Subscapular fossa on the anterior scapula. Insertion: Lesser tubercle of humerus. Innervation: Subscapular nerve. Action: Medial (internal) rotation of the humerus.

Pectoralis major: Attachments, dual innervation, and differential actions by head

Attachments: Clavicular head originates from clavicle; sternocostal head originates from sternum and costal cartilages 1-6; both insert into greater tubercle and intertubercular groove. Innervation: Medial and lateral pectoral nerves. Actions: Both heads adduct humerus; clavicular head flexes, elevates, and protracts; sternal head extends, depresses, and retracts.

Latissimus dorsi: Attachments, innervation, and actions at the humerus

Origin: Spines of T7-T12, thoracolumbar fascia. Insertion: Intertubercular groove and lesser tubercular crest. Innervation: Thoracodorsal nerve. Actions: Extends, medially rotates, and adducts the humerus.

Teres major: Attachments, innervation, actions, and rotator cuff status

Origin: Inferior angle of scapula. Insertion: Intertubercular sulcus on the anterior humerus. Innervation: Lower subscapular nerve. Actions: Adducts, extends, and medially rotates the humerus. It is NOT part of the rotator cuff.

Deltoid: Attachments, innervation, and complete contraction action

Origin: Clavicle, acromion, and spine of scapula. Insertion: Deltoid tuberosity of humerus. Innervation: Axillary nerve. Action: Abducts the humerus when all heads contract simultaneously.

Upper limb compartmentalization: Innervation and functional divide

Ventral compartment muscles are flexors innervated by the musculocutaneous, median, or ulnar nerves. Dorsal compartment muscles are extensors innervated by the radial nerve.

Axillary nerve motor supply: The three upper limb muscular exceptions

Deltoid, teres minor, and the long head of the triceps brachii.

Coracobrachialis: Attachments, innervation, and functional distinction

Origin: Coracoid process of scapula. Insertion: Medial humerus distal to deltoid tuberosity. Innervation: Musculocutaneous nerve. Actions: Flexes and adducts the humerus (does not cross the elbow joint).

Brachialis: Attachments, innervation, and action

Origin: Distal anterior flexor surface of humerus. Insertion: Coronoid process of ulna. Innervation: Musculocutaneous nerve. Action: Pure flexion of the elbow joint (lies deep to biceps brachii).

Biceps brachii: Origins, insertion, innervation, and triple actions

Origins: Supraglenoid tubercle (long head) and coracoid process (short head). Insertion: Radial tuberosity. Innervation: Musculocutaneous nerve. Actions: Flexes shoulder, flexes elbow, and supinates the forearm.

Triceps brachii: Structural heads, differing innervations, and actions

Long head originates at infraglenoid tubercle (innervated by axillary nerve; extends elbow, stabilizes/adducts shoulder). Lateral and medial heads originate from posterior humerus (innervated by radial nerve; extend elbow). All three insert on the olecranon process of the ulna.

Anconeus: Attachments, innervation, and functional relationship to triceps

Origin: Lateral epicondyle of humerus. Insertion: Olecranon process of ulna. Innervation: Radial nerve. Actions: Extends and stabilizes the elbow joint; acts as the functional upper limb equivalent to the lower limb quadriceps alongside triceps.

Brachioradialis: Attachments, innervation, and unique functional classification

Origin: Distal lateral humerus. Insertion: Styloid process of radius. Innervation: Radial nerve. Action: Flexes the elbow. Unique identity: It is the only elbow flexor located within the antebrachium.

Superficial anterior forearm flexor group: Four muscles from lateral to medial

1. Pronator teres
2. Flexor carpi radialis
3. Palmaris longus
4. Flexor carpi ulnaris (all originate from or near the common flexor tendon at the medial epicondyle).

Flexor carpi radialis vs. Flexor carpi ulnaris: Attachments, innervations, and wrist deviations

Flexor carpi radialis: Inserts on metacarpal 2, innervated by median nerve; flexes and abducts wrist (radial deviation). Flexor carpi ulnaris: Inserts on pisiform, hook of hamate, and metacarpal 5, innervated by ulnar nerve; flexes and adducts wrist (ulnar deviation).

Pronator teres and Palmaris longus: Attachments, innervations, and functions

Pronator teres: Originates at medial epicondyle and coronoid process, inserts on lateral radius, innervated by median nerve; pronates forearm and weakly flexes wrist. Palmaris longus: Originates at medial epicondyle, inserts into palmar aponeurosis, innervated by median nerve; tightens palmar aponeurosis.

Superficial posterior antebrachium extensors: Extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris

Origin: Lateral epicondyle of humerus. Innervation: Radial nerve. Actions: Extensor digitorum extends wrist and digits 2-5; extensor digiti minimi extends and abducts digit 5; extensor carpi ulnaris inserts on metacarpal 5 to extend and adduct the wrist.

Deep posterior forearm thumb muscles: Attachments, innervation, and actions

Abductor pollicis longus (inserts metacarpal 1; abducts/extends thumb), extensor pollicis brevis (inserts proximal phalanx; extends thumb), and extensor pollicis longus (inserts distal phalanx; extends thumb). All originate on dorsal radius/ulna/interosseous membrane and are innervated by the radial nerve.

Forearm supination synergy: Primary muscles and dual nerve requirement

Supinator (innervated by the radial nerve) and biceps brachii (innervated by the musculocutaneous nerve).

Wrist ulnar vs. radial deviation: Synergistic muscles and innervating nerves

Ulnar deviation (wrist adduction): Flexor carpi ulnaris (ulnar nerve) and extensor carpi ulnaris (radial nerve). Radial deviation (wrist abduction): Flexor carpi radialis (median nerve), extensor carpi radialis longus (radial nerve), and extensor carpi radialis brevis (radial nerve).