Anatomy Lab: Muscles

upper body (arms + spinal)

5 muscles of the pectoral girdle

1. deltoid

2. pectoralis major

3. latissimus dorsi

4. teres major

5. coracobrachialis

deltoid: origin, insertion, main actions on arm, innervation

• origin: lateral half of clavicle, acromion, scapular spine.

• insertion: deltoid tuberosity

• main action: ABduction, can help with all action except ADduction

• innervation: axillary (nerve)

define origin, insertion, and innervation of a muscle

origin of a muscle is fixed and proximal. insertion refers to the attachment site that moves, usually distal. innervation of a muscle refers to nerve supply (anything with an innervation is a nerve) for controlling action.

pectoralis major: origin, insertion, main action on arm, innervation

• origin: medial half of clavicle, sternum, ribs 1-6.

• insertion: intertubercular groove of humerus— lateral lip

• main actions: ADduction, flexion, medial rotation

• innervation: medial and lateral pectoral nerve

latissimus dorsi: origin, insertion, main action, innervation.

• origin: spinous processes of thoracic, lumbar and sacral vertebrae, iliac crest

• insertion: intertubercular groove of humerus (big flap of muscle up to humerus)

• main action: ADduction, extension, medial rotation

• innervation: thoracodorsal nerve (“thor has great lats”)

teres major: origin, insertion, main actions, innervation

• origin: inferior angle of scapula

• insertion: intertubuercular groove of humerus— medial lip

• main action: ADduction, medial rotation

• innervation: lower subscapular nerve

coracobrachialis: origin, insertion, main actions, innervation

• origin: coracoid process

• insertion: medial side of humeral shaft

• main actions: flexion, ADduction

• innervation: musculocutaneous nerve

rotator cuff muscles function + insertion

rotator cuff muscles are muscles on the glenohumeral joint that move the humerus and stabilize the shoulder joint; scapula to humerus

supraspinatus: origin, insertion, main actions, innervation

• origin: supraspinous fossa of scapula

• insertion: greater tubercle of humerus

• main actions: ABduction

• innervation: suprascapular

infraspinatus: origin, insertion, main actions, innervation

• origin: infraspinous fossa of scapula

• insertion: greater tubercule of humerus

• main actions: lateral rotation, ADduction

• innervation: suprascapular

teres minor: origin, insertion, main actions, innervation

• origin: lateral border of scapula

• insertion: greater tubercle of humerus

• main actions: lateral rotation, ADduction

• innervation: axillary

(right below infraspinatus)

subscapularis: origin, insertion, main actions, innervation

• origin: subscapular fossa

• insertion: lesser tubercle of humerus

• main actions: medial rotation, ADduction

• innervation: upper and lower subscapular

functions of muscles of scapula

these muscles do not act on the shoulder or arm directly, but act on the scapula, allowing for retraction, protraction, elevation, depression, and medial/lateral rotation.

trapezius: origin, insertion, main actions, innervation

• origin: occipital bone, spinous processes of C7-T12

• insertion: lateral third of clavicle, scapular spine, acromion

• main actions: retraction, medial/lateral rotation, elevation, depression, extension of neck

• innervation: cranial nerve XI

(across the back, over scapula)

Rhomboid minor: origin, insertion, main actions, innervation

• origin: spinous processes of C7 and T1

• insertion: medial border of the scapula, at the base of the scapular spine

• main actions: retraction, medial rotation

• innervation: dorsal scapular

(deep trapezius, at scapula spine)

Rhomboid major: origin, insertion, main action, innervation

• origin: spinous processes of T2-T5

• insertion: medial border of the scapula below the scapular spine

• main actions: retraction, medial rotation

• innervation: dorsal scapular

(deep trapezius, most inferior)

levator scapulae: origin, insertion, main actions, innervation

• origin: transverse processes of C1-C4

• insertion: medial border of the scapula above the scapular spine

• main actions: elevation, medial rotation

• innervation: dorsal scapular

(deep trapezius, superior of scapula)

pectoralis minor: origin, insertion, main actions, innervation

• origin: ribs 3-5

• insertion: coracoid process of scapula

• main actions: protraction, scapular stabilization

• innervation: medial pectoral

serratus anterior: origin, insertion, main actions, innervation

• origin: lateral surface of ribs 1-8

• insertion: anterior surface of medial border of scapula

• main actions: lateral rotation, protraction, holds scapula against ribcage

• innervation: long thoracic

(if connecting to lat. and is flush against rib; lat. dorsi doesn’t move scapula, but serratus anterior does)

location of corocoid brachialis

along axillary area, nerve hole.

what muscles (of pectoral/rotator cuff/scapula) are responsible for ABduction?

deltoid, supraspinatus

what muscles (of pectoral/rotator cuff/scapula) are responsible for ADduction?

pectoralis major, latissimus dorsi, teres major, coracobrachialis, infraspinatus, teres minor, subscapularis

what muscles (of pectoral/rotator cuff/scapula) are responsible for flexion?

pectoralis major, coracobrachialis, deltoid (only pectoral girdle muscles)

what muscles (of pectoral/rotator cuff/scapula) are responsible for extension?

only lattisimus dorsi, deltoid

what muscles (of pectoral/rotator cuff/scapula) are responsible for lateral rotation?

infraspinatus, teres minor, trapezius, serratus anterior, deltoid

what muscles (of pectoral/rotator cuff/scapula) are responsible for retraction?

rhomboid minor/major, trapezius (only muscles that act on scapula)

what muscles (of pectoral/rotator cuff/scapula) are responsible for protraction?

pectoralis minor, serratus anterior