Thoracic Limb - Intrinsic Muscles - Attachments and Actions

supraspinatus

attachments: supraspinous fossa of the scapula, greater tubercle of the humerus actions: extend/stablize the shoulder

deltoideus

attachments: spine and acromion of the scapula, deltoid tuberosity

actions: flex the shoulder joint

infraspinatus

attachments: infraspinatous fossa of the scapula, greater tubercle of the humerus actions: flex/stablize the shoulder, abduct the limb at the shoulder joint

what does trauma of the infraspinatus lead to?

fibrosis of the m., resulting in external rotation and extension of the shoulder joint, called infraspinatus contracture

teres minor

attachments: caudal aspect of scapula, teres minor tuberosity of humerus

actions: flex the shoulder joint

subscapularis

attachments: subscapular fossa of the scapula, lesser tubcerle of the humerus

actions: shoulder stabilizer, adducts limb at the shoulder joint

teres major

attachments: caudal border of the scapula, teres major tuberosity of humerus

actions: flex the shoulder joint

coracobrachialis

attachments: coracoid process of scapula, lesser tubercle and teres major tuberosity of humerus

actions: stablize the shoulder joint

what holds the biceps tendon in place?

held in the intertubercular grooves by a band of fibrous connective tissue, the transverse humeral retinaculum

biceps brachii

attachments: supraglenoid tubercle of scapula, proximal radius and ulna. in combo w/ the the tendon of the brachialis muscle

actions: flex the elbow joint, extend the shoulder joint

brachialis

attachments: proximal humerus and medial aspect proximal radius and ulna

actions: flex the elbow joint

tensor fascia antebrachii

attachments: fascia on the lateral surface of the latissimus dorsi and olecranon

actions: extend the elbow joint

what is the largest muscle of the brachium?

the triceps brachii

how is the the bursa related to the triceps important clinically?

it lies between the tendon and tuberosity. The sq bursa of the olecranon can fill w/ synovial fluid as a reaction to excess strain. It may be visible as a tense plum swelling up to an egg size at the olecranon

triceps - long head

attachments: caudal border of scapula to tuber olecrani

actions: extend the elbow joint, flexes the shoulder joint

triceps - lateral head

attachments: tricipital line of humerus to tuber olecrani

actions: extend the elbow joint

triceps - medial head

attachments: crest of the lesser tubercle to tuber olecrani

actions: extend the elbow joint

triceps - accessory head

attachments: neck of humerus to tuber olecrani

actions: extend the elbow joint

What muscle mass is occasionally used for IM injections, especially in larger dogs?

the triceps

anconeus

attachments: lateral supracondylar crest and epicondyle of the humerus to the olecranon

actions: extend the elbow joint

What is the clinical important of the anconeus?

It is elevated from the lateral epicondyle of the humerus to gain access to the elbow joint for removal of an ununited anconeal process.

what are the pads, in order of proximal to distal?

1 carpal pad → 1 metacarpal pad → 4 digital pads

extensor carpi radialis

attachments: lateral epicondyle of the humerus, metacarpal bones II and III

actions: extend the carpal joints, minimally aids in flexion of the elbow joint

what is the extensor retinaculum?

a band of collagenous connective tissue that binds down the tendons of the extensor carpi radialis and other extensor muscles over the carpus

common digital extensor

attachments: lateral epicondyle of the humerus and distal phalanges of the weight bearing digits (II-V)

actions: extend the carpal and digital joints

what is the landmark for exposure of the radius in fracture repair?

the separation between the extensor carpi radialis and the common digital extensor

lateral digital extensor

attachments: lateral epicondyle of the humerus and distal phalanges of digits III-V

actions: extend the carpal joints and digital joints III-V

ulnaris lateralis

attachments: lateral epicondyle of the humerus and metacarpal bone V, accessory carpal bone

actions: flex the carpal joints, abduct the manus at the carpal joints

supinator

attachments: lateral epicondyle of the humerus and radius

actions: supinate the antebrachium and manus, aids in flexion of elbow joint

abductor pollicis longus

attachments: holds down the tendon of the extensor carpi radialis m. along its course to the 1st metacarpal bone

actions: abducts the 1st digit, extends the carpus

pronator teres

attachment: medial epicondyle of the humerus, proximal medial radius

action: pronate the antebrachium and manus, aids in flexion of elbow joint

flexor carpi radialis

attachments: medial epicondyle of the humerus, metacarpal bones II and III

action: flex the carpal joints

flexor carpi ulnaris

attachments: medial epicondyle of the humerus, caudomedial surface of the olecranon and accessory carpal bone

action: flex the carpal joints

superficial digital flexor

attachments: medial epicondyle of the humerus and palmar surface of the middle phalanx of the weight-bearing digits (II-V)

action: flex the carpal joints, flex the metacarpophalangeal joints and the proximal interphalangeal joints of the weight-bearing digits (II-V)

deep digital flexor

attachments: medial epicondyle of the humerus, caudal border of the ulna, medial border of the radius and distal phalanx of all 5 digits (I-V)

action: flex the carpal joints, flex the digital joints of all 5 digits (I-V)

what is special about the brachioradialis in cats?

it’s well developed. It is long, narrow, and band-like, passing along the medial border of the forearms.

attachments: originates on the humerus, inserts on the radius

action: flex the elbow, but can also pronate or supinate depending on the position of the arm

What keeps a cat’s claws retracted?

2 dorsal elastic ligaments at the distal interphalangeal joints that are highly modified

• when retracted, the distal phalanx moves to a position lateral to the middle phalanx

  • when unsheathing the claw, the deep digital flexor m. must contract enough to overpower the elastic ligaments

Where does the lateral digital extensor m. terminate in cats?

on digits II-V

What is special about the supinator in cats?

It’s well-developed, giving it a greater ability to supinate. Useful in defense, climbing, and grooming

What’s the difference in the deep digital flexor between a cat and dog?

In a cat, the radial and ulnar heads are relatively similar in size to each other, and much larger than in the dog.