Muscle Anatomy of the Forelimb

Superficial Pectoral Muscle

Origin: First two sternebrae;

Insertion: greater tubercle;

Innervation: Cranial pectoral nerves (C7, C8);

Action: Adducts the forelimb.

Deep Pectoral Muscle

Origin: Ventral part to caudal part of the sternum

Insertion: greater tubercle and partly on the lesser tubercle of the humerus;

Innervation: Caudal pectoral nerves (C8, T1);

Action: Adducts the forelimb, draws the limb caudally, and flexes the shoulder joint.

Brachiocephalicus

Origin: vestigial clavicle

Insertion: Distal cranial border of the humerus

Innervation: Accessory and cervical spinal nerves;

Action: Protracts the forelimb and extends the shoulder.

Omotransversarius

Origin: Transverse wing of the atlas

Insertion: Distal end of the spine of the scapula;

Innervation: Accessory nerve;

Action: Protracts the limb and flexes the neck laterally.

Trapezius

Origin: Median raphe of the neck and supraspinous ligament from C3-C9;

Insertion: Spine of the scapula;

Innervation: Accessory nerve;

Action: Elevates and abducts the forelimb.

Rhomboideus

Origin: Median fibrous raphe of the neck and spinous processes of thoracic vertebrae;

Insertion: Dorsal border of the scapula;

Innervation: Ventral branches of cervical and thoracic spinal nerves;

Action: Elevates the forelimb

Latissimus Dorsi

Origin: Thoracolumbar fascia from the spinous processes of lumbar and T7/8;

Insertion: Teres major tuberosity of the humerus;

Innervation: Thoracodorsal nerve (C7, C8, T1);

Action: Retracts the limb, flexes the shoulder.

Serratus Ventralis

Origin: Transverse processes of C3-7 and first seven/eight ribs ventral to their middle;

Insertion: Serrated face of the scapula;

Innervation: Long thoracic nerve and ventral branches of cervical spinal nerves;

Action: Cranial part retracts, caudal part protracts forelimb

Deltoideus

Origin: Spine and acromion of the scapula;

Insertion: Deltoid tuberosity of the humerus;

Innervation: Axillary nerve;

Action: Flexes the shoulder.

Infraspinatus

Origin: Infraspinous fossa of the scapula;

Insertion: Lateral greater tubercle of the humerus;

Innervation: Suprascapular nerve;

Action: Flexes and extends the shoulder joint.

Teres Minor

Origin: Infraglenoid tubercle and distal caudal border of the scapula;

Insertion: Teres minor tuberosity of the humerus;

Innervation: Axillary nerve;

Action: Flexes the shoulder joint and rotates the arm laterally.

Supraspinatus

Origin: Supraspinous fossa of the scapula;

Insertion: Greater tubercle of the humerus;

Innervation: Suprascapular nerve;

Action: Extends and stabilizes the shoulder joint.

Subscapularis

Origin: Subscapular fossa of the scapula;

Insertion: Lesser tubercle of the humerus;

Innervation: Subscapular nerve;

Action: Adducts and extends shoulder joint.

Teres Major

Origin: Caudal angle and border of the scapula;

Insertion: Teres major tuberosity of the humerus;

Innervation: Axillary nerve;

Action: Flexes the shoulder joint and rotates the arm medially.

Coracobrachialis

Origin: Coracoid process of the scapula;

Insertion: lesser tubercle of the humerus;

Innervation: Musculocutaneous nerve;

Action: Adducts limb, extends shoulder joint

Tensor Fasciae Antebrachii

Origin: Fascia of lateral latissimus dorsi;

Insertion: Olecranon of the ulna;

Innervation: Radial nerve;

Action: Extends the elbow joint.

Triceps Brachii (Long Head)

Origin: Caudal border of the scapula;

Insertion: Olecranon of the ulna;

Innervation: Radial nerve.

Action: Extends the elbow joint and flexes shoulder

Triceps Brachii (Lateral Head)

Origin: Tricipital line of the humerus;

Insertion: Olecranon of the ulna;

Innervation: Radial nerve;

Action: Extends the elbow joint.

Triceps Brachii (Accessory Head)

Origin: Neck of the humerus;

Insertion: Olecranon of the ulna;

Innervation: Radial nerve;

Action: Extends the elbow joint.

Triceps Brachii (Medial Head)

Origin: lesser tubercle

Insertion: Olecranon of the ulna;

Innervation: Radial nerve;

Action: Extends the elbow joint.

Anconeus

Origin: Supracondylar crest and the lateral and medial epicondyles of the humerus;

Insertion: olecranon;

Innervation: Radial nerve;

Action: Extends the elbow joint.

Biceps Brachii

Origin: Supraglenoid tubercle of the scapula;

Insertion: Ulnar and radial tuberosities;

Innervation: Musculocutaneous nerve;

Action: Flexes the elbow joint and extends the shoulder joint

Brachialis

Origin: Proximal lateral surface of the humerus;

Insertion: Ulnar and radial tuberosities;

Innervation: Musculocutaneous nerve;

Action: Flexes the elbow joint.

Extensor Carpi Radialis

Origin: Lateral supracondylar crest of the humerus;

Insertion: Proximodorsal surfaces of metacarpals II and III;

Innervation: Radial nerve;

Action: Extends the carpus.

Common Digital Extensor

Origin: Lateral epicondyle of the humerus;

Insertion: Extensor processes of the distal phalanges II-V;

Innervation: Radial nerve;

Action: Extends the carpus and digits.

Lateral Digital Extensor

Origin: Lateral epicondyle of the humerus;

Insertion: Proximal ends of all the phalanges III-V;

Innervation: Radial nerve;

Action: Extends the carpus and digits III-V.

Ulnaris Lateralis

Origin: Lateral epicondyle of the humerus;

Insertion: Accessory carpal bone and the lateral aspect of metacarpal V;

Innervation: Radial nerve;

ction: Flexes and abducts the carpus.

Supinator

Origin: Lateral epicondyle of the humerus;

Insertion: Cranial surface of the radius;

Innervation: Radial nerve;

Action: Rotates the forearm laterally (supination) and flexes the elbow joint.

Abductor Digiti Longus

Origin: Craniolateral surface of the ulna;

Insertion: Proximal end of metacarpal I and II;

Innervation: Radial nerve;

Action: Abducts the first digit and extends the carpus.

Pronator Teres

Origin: Medial epicondyle of the humerus;

Insertion: Medial border of the radius;

Innervation: Median nerve;

Action: Rotates the forearm medially (pronation) and flexes the elbow joint.

Flexor Carpi Radialis

Origin: Medial epicondyle of the humerus and medial border of the radius;

Insertion: Palmar side of metacarpals II and III;

Innervation: Median nerve;

Action: Flexes the carpus.

Superficial Digital Flexor

Origin: Medial epicondyle of the humerus;

Insertion: Palmar surface of the base of the middle phalanges II-V;

Innervation: Median nerve;

Action: Extends elbow, flexes the carpus and digits II-V.

Flexor Carpi Ulnaris (Ulnar and Humeral Heads)

Origin:

Ulnar head - olecranon;

Humeral head - medial epicondyle of the humerus;

Insertion: Accessory carpal bone;

Innervation: Ulnar nerve;

Action: Flexes the carpus.

Deep Digital Flexor (Humeral, Ulnar, and Radial Heads)

Origin:

Humeral head - medial epicondyle of the humerus;

Ulnar head - proximal caudal border of the ulna;

Radial head - medial border of the radius;

Insertion: Flexor surface of the distal phalanx III;

Innervation: Median and ulnar nerves;

Action: Flexes the carpus and the digits.

Pronator Quadratus

Origin: Fills space between radius and ulna;

Insertion: Apposed surfaces of the radius and ulna;

Innervation: Median nerve;

Action: Pronates the paw.

Interosseous

Origin: base metacarpal bones II-V;

Insertion: Metacarpophalangeal joint;

Innervation: Deep branch of Ulnar nerve;

Action: Flexes the metacarpophalangeal joint.