Shoulder Joint Including Chest Muscles

Shoulder joint including Chest Muscles

  • Pectoralis Major / LatissimusDorsi / 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

LatissimusDorsi

The Latissimusdorsi 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

  • Supraspinousfossa

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 Latissimusdorsi.

Origin

  • lower 1/3 of the lateral border of the scapula

Insertion

  • Intertuberculargoove (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
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