Thoracic Limb Muscles

Flashcards for the muscles of the thoracic limb

Latissimus Dorsi

• Origin: spinous processes of the first 7 thoracic vertebrae
• Insertion: crest of the lesser tubercle of the humerus
• Action: Flexes the shoulder joint, draw limb caudally (digging)

Biceps Brachii

• Origin: Supraglenoid tubercle of the scapula
• Insertion: Radial tuberosity
• Action: Flex the elbow joint, extend the shoulder joint

Teres Minor

• Origin: Lateral border of the scapula
• Insertion: Deltoid tuberosity of the humerus
• Action: NWB: Flex the shoulder / rotate the shoulder laterally WB: Prevent medial rotation

Triceps Brachii (Lateral head)

• Origin: Lateral surface of the humerus
• Insertion: Olecranon process of the ulna
• Action: Extend the elbow joint

Triceps Brachii (Long head)

• Origin: Infraglenoid tubercle of the scapula
• Insertion: Olecranon process of the ulna
• Action: Extend the elbow joint, flex the shoulder joint

Triceps Brachii (Medial head)

• Origin: Medial surface of the humerus
• Insertion: Olecranon process of the ulna
• Action: Extends the elbow joint

Ulnaris Lateralis (Extensor Carpi Ulnaris)

• Origin: Lateral epicondyle of the humerus
• Insertion: Accessory carpal bone
• Action: NWB: Abduct the manus, flex the carpal joints WB: Support the carpus

Supraspinatus

• Origin: Supraspinous fossa of the scapula
• Insertion: Greater tubercle of the humerus
• Action: Extend and stabilize the shoulder joint

Infraspinatus

• Origin: Infraspinous fossa of the scapula
• Insertion: Greater tubercle of the humerus
• Action: NWB: Extend or flex shoulder joint (depending on the degree of extension or position of the joint during contraction) and abduct the shoulder / rotate the humerus laterally WB: Prevent medial rotation and provide lateral stability to the shoulder joint

Platysma

• Origin: Sternum, raphe of the mandible
• Insertion: Skin of the neck and face
• Action: Facial expression, skin movement

Supinator

• Origin: Lateral epicondyle of the humerus
• Insertion: Distal radius and ulna
• Action: Rotate the forearm laterally so that the palmar side of the paw faces medially (supination), flex the elbow joint

Omotransversarius

• Origin: transverse processes of C3-C7
• Insertion: acromion and spine of scapula
• Action: Elevates and abduct the limb