Shoulder Muscles in Shoulder Girdle

Question 1

Pectoralis Minor
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 1

Origin
- Anterior and superior surfaces of ribs 3, 4, 5

Insertion
- Coracoid process of scapula

Nerve supply
- Medial and Lateral pectoral nerves, C5-8 and T1

Action
- Shoulder girdle depression
- Shoulder girdle protraction
- Accessory muscle of respiration

Question 1

Subclavius Muscle
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 1

Origin
- Costochondral junction of 1st rib

Insertion
- Inferior surface of middle 1/3 clavicle

Nerve supply
- Subclavian Nerve (C5, C6)

Action
- Stabilises STERNOCLAVICULAR joint
- Depresses lateral end of clavicle
- Not much in physiological movement

Question 2

Serratus Anterior
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 2

Origin
- Anterior (costal) surface of the medial of scapula

Insertion
- Lateral surface of upper 8-9 ribs

Nerve supply
- Long Thoracic nerve (C5, C7)

Action
- Shoulder girdle protraction
- Lateral rotation of scapula

Question 3

What are the attachments for the Trapezius muscle and what is the nerve supply?

Answer 3

Origin
- Superior nuchal line on the skull and external occipital protuberance
- Ligamentum Nuchae - runs down to posterior neck
- Spinous processes of C7 to T12
- Supraspinous ligament

Insertion
- Lateral 1/3 upper clavical
- Acromion and spine of scapula (middle)
- Medial end of scapula spine (lower)

Nerve supply
- Accessory nerve C3-4

Question 4

What are the actions of the Trapezius muscle?

Answer 4

Action
- Elevation of shoulder girdle (upper)
- Lateral rotation of scapula (upper and lower)
- Retraction of shoulder girdle (middle)
- Depression of shoulder girdle (lower)
- Cervical side flexion (upper-unilateral)
- Cervical extension (upper-bilateral)

Question 5

What is the function of the Trapezius muscle?

Answer 5

Function
- Important muscle
- Steadies scapula and clavicle against gravity
- Provides fixation of the neck/head
- Laterally rotates scapula
- Retracts scapula
- Depression of scapula against resistance

Question 6

Levator Scapulae
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 6

Origin
- Superior portion of medial border of scapula

Insertion
- Transverse processes of C1-4

Nerve supply
- Dorsal Scapular Nerve C4-5

Action
- Elevation of shoulder girdle
- Medial rotation of scapula
- Cervical extension (bilateral)
- Cervical side flexion (unilateral)

Question 7

Rhomboid Minor
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 7

Origin
- Spinous processes of C7-T1
- Ligamentum Nuchae

Insertion
- Medial border of scapula at root of spine

Nerve supply
- Dorsal Scapular nerve (C4-5)

Action
- Elevation of scapula
- Retraction of scapula

Question 8

Rhomboid Major
- What are the attachments?
- What is its innervation?
- What action does it do?

Answer 8

Origin
- Spinous processes of T2-5
- Intervening supraspinous ligaments

Insertion
- Medial border of scapula from root of spine to inferior angle
- Lower portion of scapula

Nerve supply
- Dorsal Scapular nerve (C4-5)

Action
- Elevation of scapula
- Retraction of scapula