VMED 5163 - Comparative Thoracic Limb Muscles and Passive Stay Apparatus

Superficial pectorals, deep pectoral, and subclavius mm.

What muscles are included in the pectoral group?

Descending and transverse pectorals

There are two portions of the superficial pectoral muscle. What are they?

Horses

The subclavius muscle is most developed in which species?

Serratus ventralis m.

A condition known as a "flying scapula" or "winged scapula" is caused by an injury in which muscle?

Accessory head

Which head of the triceps is considered 'missing' in the horse?

Lacertus fibrosus; joins with the extensor carpi radialis m.

The continuation of the biceps tendon is known as the ___. What muscle does this tendon join distally?

It is associated with the stay apparatus and prevention of shoulder flexion

Why is the lacertus fibrosis more prominent in the horse than other ungulates?

Ruminants

The common digital extensor m. has two bellies in which animals?

Medial belly; inserts on digit III

Which portion of the common digital extensor m. is larger in ruminants? On which digit does this belly insert?

Lateral belly

Which muscle belly of the common digital extensor m. is associated with both digits?

One in horses, two in ruminants

How many portions does the superficial digital flexor have in horses? Ruminants?

The carpal canal

In ruminants, the deep belly of the superficial digital flexor passes through what structure?

Proximal check ligament, superior check ligament, or radial check ligament

The check ligament of the superficial digital flexor can be called by what other names?

Humeral, radial, and ulnar heads

What are the different bellies of the deep digital flexor muscle?

Deep digital flexor m.

The distal check ligament is associated with what muscle?

Metacarpal III and DDF

The inferior check ligament attaches to what structures?

Flexor manica

The place where the superficial digital flexor splits and encases the deep digital flexor tendon is known as the?

Horses spend most of the day standing, and this system allows them to doze while preventing collapse and with minimal energy use

Why is the stay apparatus necessary in the horse?

Flexion

In the shoulder joint, (flexion/extension) is prevented via the stay apparatus

Internal tendon of the biceps brachii m.

Which structures prevent collapse of the shoulder joint in the stay apparatus?

It is thickened (fibrocartilaginous) and under tension, pulled tightly over the intermediate tubercle

What characteristics allow the internal biceps tendon to prevent shoulder flexion?

The radial tuberosity of metacarpal III

The lacertus fibrosus inserts at what bony prominence?

Fascia

The lacertus fibrosus and the extensor carpi radialis m. are connected via?

Flexion

Collapse of the front limbs would lead to the ___ of the elbow joint

Tension in carpal and digital flexors, and the location of the collateral ligaments being slightly caudal to the point of rotation

Collapse of the elbow joint is prevented by what structures?

Biceps brachii m.

When at rest, collateral ligaments keep the elbow joint from collapsing. Flexion of which muscle causes stretching of these ligaments, ending in flexion?

Carpus

Hyperextension of which joint is prevented by the flexor retinaculum?

Shape of carpal bones, palmar carpal ligament, superficial and deep digital flexor tendons and check ligaments, flexor retinaculum

What structures assist in keeping the carpus in place?

Sling

Flexor tendons and the suspensory apparatus of the distal limb act as a?

Hyperextension

The stay apparatus prevents the fetlock joint from what?

Suspensory apparatus, superficial and deep digital flexor tendons, and annular ligament

What structures of the stay apparatus are associated with the fetlock?

Interosseus III

The suspensory ligament, also known as the ___, has extensor branches which resist flexion

Palmar annular ligament

The most proximal ligament of the fetlock is the?

Intersesamoidean ligament

The hardened, ossified piece of cartilage between the proximal sesamoid bones is known as the?

Palmar annular, proximal digital annular, distal annular digital ligaments

What annular ligaments are present in the fetlock?

Straight sesamoidean ligament; oblique sesamoidean ligaments

Continuing from the intersesamoidean ligament is the ____, which is surrounded by what structures?

Hyperextension

Collapse of the thoracic limb would lead to (flexion/hyperextension) of the pastern joint

Palmar ligament of the pastern, straight sesamoidean ligament, and deep digital flexor tendon

What structures of the suspensory apparatus are associated with the pastern?

Tension on the deep digital flexor tendon, and annular ligaments

Hyperextension of the coffin joint is prevented by which structures?