Back Muscles - Extrinsic

Question 1

Trapezius

Origin (Proximal)

Insertion (Distal)

Action

Answer 1

Origin:

• Medial 3rd of sup. nuchal line
• Ext. occip. protuberance
• Nuchal lig.
• SP of C7-T12

Insertion:

• Lateral 3rd of clavicle
• Acromion & spine of scapula

Action:

• Descending: elevates shoulder complex
• Middle: retracts scapula
• Ascending: depresses shoulder complex

Question 2

Latissimus Dorsi

Origin (Proximal)

Insertion (Distal)

Action

Answer 2

Origin:

• SP of T7/T8-T12
• Thoracolumbar fascia
• Iliac crest
• Inf. 3/4 ribs

Insertion:
-Floor of inter tubercular sulcus of humerus (anterior side)

Action:

• Extends/adducts/medially rotates humerus
• Raises body to arm while climbing

Question 3

Levator Scapulae

Origin (Proximal)

Insertion (Distal)

Action

Answer 3

Origin:
-Posterior tubercles of TP of C1-C4

Insertion:
-Medial border of scapular spine superior to root of scapular spine

Action:

• Elevates scapula
• Tilts glenoid cavity inferiorly by rotating scapula

Question 4

Rhomboid Minor

Origin (Proximal)

Insertion (Distal)

Action

Answer 4

Origin:

• Nuchal lig.
• SP of C7-T1

Insertion:
-Smooth triangular area at medial end of scapular spine

Action:

• Retract scapula
• Rotate scapula to depress glenoid cavity [like levator scap.]
• Fixes scapula to thoracic wall

Question 5

Rhomboid Major

Origin (Proximal)

Insertion (Distal)

Action

Answer 5

Origin:
-SP of T2-T5

Insertion:
-Medial border of scapula from spine to inferior angle

Action:

• Retract scapula
• Rotate scapula to depress glenoid cavity [like levator scap.]
• Fixes scapula to thoracic wall

Question 6

Serratus Posterior Superior

Origin (Proximal)

Insertion (Distal)

Action

Answer 6

Origin:
-Nuchal lig. & SP of C7-T3

Insertion:
-Sup. borders of ribs 2-4

Action:

• Proprioception
• Elevate/depress ribs

Question 7

Serratus Posterior Inferior

Origin (Proximal)

Insertion (Distal)

Action

Answer 7

Origin:
-SP of T11-L2

Insertion:
-Inf. borders of ribs 8-12 near angles

Action:

• Proprioception
• Elevate/depress ribs

Question 8

What is the trapezius innervated by?

Answer 8

Cranial nerve XI: the spinal accessory nerve

Question 9

What is the latissimus dorsi innervated by?

Answer 9

Thoracodorsal nerve (beneath teres major)

Question 10

What are the rhomboids/levator scapulae innervated by?

Answer 10

Dorsal scapular nerve (between scapula and thoracic wall)