Innervated by: Accessory n.
Origin: transverse processes of the atlas
Insertion: acromion and distal spine of the scapula
Action: advancing the limb

Innervated by: Accessory n.
There are two parts separated by the clavicle.
Origin: clavicle and cranial humerus
Insertion: median raphe of the neck and the occipital bone. The ventral part attaches to the mastoid process.
Actions: advances the limb and extends the shoulder joint when the limb is in motion; draws the head and neck ventrally when the limb is fixed.

Photo 1

Innervated by: Accessory n.
Origin: mid-dorsal raphe of the neck and supraspinous ligament
Insertion: spine of the scapula
Body: two parts, cervical and thoracic separated by aponeurosis
Action: elevates limb and swings cranially to advance the limb

Innervated by: local branch of brachial plexus
Origin: thoracolumbar fascia
Insertion: teres tuberosity and greater tubercle of the humerus
Actions: antagonist to the brachiocephalic m. To draw the limb forward and possibly laterally; depression of the vertebral column; support the limb, draw the limb against the trunk, draw the free limb backward during flexion of the shoulder joint.

Photo 2

Innervated by: brachial plexus
Origin: nuchal ligament, 4th - 6th thoracic spine
Insertion: dorsal border and adjacent scapula
Action: Pull limb and shoulder forward or backward, may also raise limb.

Innervated by: brachial plexus
Origin: Cranial sternum
Insertion: Part 1 - descending and transverse - greater tubercle. Part 2 - Lesser tubercle.
Action: adduct the forelimb, assist in protraction and retraction.

Photo 3

Innervated by: branch of brachial plexus
Origin: transverse processes of C4 to 10th rib
Insertion: medial scapula and scapular cartilage
Action: supporting the weight of the trunk. It is reinforced by strong fascia. The cervical portion can retract the limb and the caudal portion can advance the limb.

O: Cranial border of the first rib.
I: Transverse processes of the seventh cervical vertebra and wing like process of the sixth cervical vertebra.
A: Draws the neck downward. In unilateral action, to bend the neck sideward. When the neck is fixed, the supracostal part can act in inspiration.

Photo 4

Innervated by: Radial n. from the brachial plexus
Origin: tendon and lateral surface of the latissimus dorsi

Muscles that create a "muscular sling" for the forelimb?

Photo 5