Shoulder joint including Chest Muscles

Pectoralis Major / Latissimus Dorsi / Deltoid / Supraspinatus / Infraspinatus / Teres Minor /
Subscapularis / Teres Major
Pectoralis Major Chest Muscle
Pectoralis major is the largest and most superficial of the two chest muscles. Pec major and the
anterior fibres of Deltoid work closely together. Pec fly and push-up exercises work the Pectoralis
major.
Origin

Medial 1/2 of the clavicle

Costal cartilages of the first 6 ribs

Sternum
Insertion

Intertubercular groove (between the greater and lesser tubercles) of the humerus
Actions

Shoulder flexion

Internal rotation

Adduction
Innervation

Lateral and medial pectoral nerves
Daily uses

Using roll-on deoderant
Latissimus Dorsi
The Latissimus dorsi muscle is one of the largest in the body. It is a powerful extensor muscle of the
arm and is used extensively in chinning and climbing. They are commonly known at the lats.
Origin

Posterior crest of the ilium (via the Thoracolumbar fascia)

Posterior sacrum

Spinous processes of T7-L5
Insertion

Intertubercular groove (between the greater and lesser tuberosities) of the humerus
Actions

Extension

Internal rotation

Adduction
Innervation

Thoracodorsal nerve
Daily uses

Pushing on the arms of a chair when standing up
Deltoid
The deltoid muscle is used in all side lifting movements and any movement of the humerus on the
scapula. It is divided into two portions, anterior and posterior, with the fibres having different roles
due to their orientation.
Origin

Outer 1/3 of the clavicle

Acromion process

Spine of the scapula
Insertion

Deltoid tuberosity on the humerus
Actions

Anterior portion - Shoulder flexion and internal rotation

Posterior portion - Shoulder extension and external rotation

All fibres - Shoulder abduction
Innervation

Axillary nerve
Daily uses

Lifting
Supraspinatus Muscle
The Supraspinatus muscle is one of the four muscles which make up the rotator cuff. Its main
function is to stabilise the humerus by holding the head of the humerus in position.
It is important in throwing motions to control any forward motion of the head of humerus.
Origin

Supraspinous fossa
Insertion

Greater tuberosity of the humerus
Actions

Abduction

Stabilisation of the humerus
Innervation

Suprascapular nerve
Daily uses

Holding shopping bags away from the body
Infraspinatus
The Infraspinatus muscle is one of the four rotator cuff muscles and is commonly injured. It is the
main external rotator of the shoulder joint and works in conjunction with the Terres Minor.
Origin

Posterior surface of the scapula (below the spine of the scapula)
Insertion

Greater tuberosity on the humerus
Actions

Shoulder abduction

External rotation
Innervation

Suprascapular nerve
Daily uses

Brushing hair
Teres Minor
Teres Minor is one of the four rotator cuff muscles. Its main action, along with Infraspinatus is to
externally rotate the shoulder joint. There are two Teres muscles, the other being Teres Major.
Origin

Mid section of the lateral border of the scapula
Insertion

Greater tuberosity on the humerus
Actions

External rotation

Shoulder abduction
Innervation

Axillary nerve
Daily uses

Brushing hair
Subscapularis Muscle
Subscapularis is one of the four rotator cuff muscles. The muscle also acts to hold the head of the
humerus in position and prevents it moving forwards.
Origin

Anterior (costal) surface of the scapula
Insertion

Lesser tuberosity of the humerus
Actions

Internal rotation

Adduction
Innervation

Upper and lower subscapular nerves
Daily uses

Tucking the back of your shirt into your trousers
Teres Major Muscle
Teres major is only functional when the Rhomboids fix the scapula. This muscle mainly helps
Latissimus dorsi.
Origin

lower 1/3 of the lateral border of the scapula
Insertion

Intertubercular goove (between the greater and lesser tubercles) of the humerus
Actions

Adduction

Internal rotation

Extension
Innervation

Lower subscapular nerve
Daily uses

Tucking the back of your shirt into your trousers