The Muscular SystemMuscle of the Shoulder and Upper Limbs

Two major muscle groups of the back and shoulder:

1. The trapezius group 2. The deltoid group

Trapezius muscle group

Large superficial muscleOrigin:

Occipital bone and spinous process of thoracic vertebrae

Insertion: Clavicle and scapula

Action: on scapula

Trapezius muscle group (in cats)

1. Clavotrapezius Elevates and

retracts scapula Extends forearm

in forward motion

Three separate trapezius muscles in cat compared to one in human:

Trapezius muscle group (in cats)

2. Acromiotrapezius

Adducts the scapula

Three separate trapezius muscles in cat compared to one in human:

Trapezius muscle group (in cats)

3. Spinotrapezius Adduct scapula

and pulls it posteriorly

Three separate trapezius muscles in cat compared to one in human:

Deltoid muscle (in humans)

Origin: Spine of scapula

Insertion: Deltoid tuberosity of

humerusAction:

Shoulder abduction, flexion, extension, rotation

Deltoid muscle (in cats)

1. Clavobrachialis (aka clavodeltoid)

Flexes the forearm abduction

Three separate deltoid muscles in cat compared to one in human:

Deltoid muscle (in cats)

2. Acromiodeltoid Flexes the

humerus and rotates it outward

Three separate trapezius muscles in cat compared to one in human:

Deltoid muscle (in cats)

3. Spinodeltoid Acts in synergy

with acromiodeltoid

Three separate trapezius muscles in cat compared to one in human:

Levator Scapulae VentralisAction:

Elevates scapula

Origin: Transverse process

of first 4 cervical vertebrae

Insertion: Vertebral border of

scapula

Latissimus dorsi

Action: pulls forelimb dorsocaudally

Origin: last 6 thoracic vertebrae, all lumbar

vertebrae and iliac crest

Insertion: intertubercular groove of humerus

Ventral View

clavotrapezius

clavobrachialisPectoralis

majorPectoantebrachialis