Muscle of the Shoulder and Upper Limbs

1. The trapezius group 2. The deltoid group

 Large superficial muscle  Origin:  Occipital bone and spinous process of thoracic vertebrae  Insertion:  Clavicle and scapula  Action: on scapula

1. Clavotrapezius  Elevates and retracts scapula  Extends forearm in forward motion Three separate trapezius muscles in cat compared to one in human:

2. Acromiotrapezius  Adducts the scapula Three separate trapezius muscles in cat compared to one in human:

3. Spinotrapezius  Adduct scapula and pulls it posteriorly Three separate trapezius muscles in cat compared to one in human:

 Origin:  Spine of scapula  Insertion:  Deltoid tuberosity of humerus  Action:  Shoulder abduction, flexion, extension, rotation

1. Clavobrachialis (aka clavodeltoid)  Flexes the forearm  abduction Three separate deltoid muscles in cat compared to one in human:

2. Acromiodeltoid  Flexes the humerus and rotates it outward Three separate trapezius muscles in cat compared to one in human:

3. Spinodeltoid  Acts in synergy with acromiodeltoid Three separate trapezius muscles in cat compared to one in human:

 Action:  Elevates scapula  Origin:  Transverse process of first 4 cervical vertebrae  Insertion:  Vertebral border of scapula

 Action:  pulls forelimb dorsocaudally  Origin:  last 6 thoracic vertebrae, all lumbar vertebrae and iliac crest  Insertion:  intertubercular groove of humerus

clavotrapezius clavobrachialis Pectoralis major Pectoantebrachialis