Lecture 9: Extrinisc Back Muscles

Question 0

Trapezius slide 11

Answer 0

Proximal attachment
Meidal third of superior nuchal line; external occiptal protuberance; nuchal ligament; spinous processes of C7-T12 vertebrae

Distal attachment
Lateral third of clavicle; acromion and spine of scapula

Innervation
Motor: Spinal accessory nerve (CN XI)
Sensory: C3 & C4 spinal nerves

Main actions
Descending part elevates; ascending part depresses; middle part (or all parts together) retracts scapula;
Descending and ascending parts together rotate glenoid cavity superiorly.

Question 1

Name the superficial extrinsic back muscles

Answer 1

Trapezius 
Lattissimus Dorsi 
Levator scapulae 
Rhomboid major 
Rhomboid minor

Question 2

Lattissimus Dorsi

Slide 13

Answer 2

Proximal attachment
Spinous processes of T7 to T12, thoracolumbar fascia, iliac crest, ribs 10-12

Distal attachment
Floor of intertubular sulcus of humerus

Innervation
Thoracodorsal nerve
(C6, C7, C8)

Main actions
Extends, adducts and medially rotates humerus
Raises body toward arms during climbing

Question 3

Lavator scapulae slide 16

Answer 3

Proximal attachment
Posterior tubercles of transverse processes of C1-C4 vertebrae

Distal attachment
Medial border of scapula superior to root of scapular spine

Innervation
Dorsal scapular (C5) and cervical (C3, C4) nerves

Main actions
Elevates scapula
Tilts glenoid cavity inferiorly (by rotating scapula)

Question 4

Rhomboid major slide 18

Answer 4

Proximal attachment
Spinous processes
of T2-T5 vertebrae
Distal attachment
Medial border of scapula from level of spine to inferior angle

Innervation
Dorsal scapular nerve
(C4, C5)

Main actions
Retracts scapula and rotate it to depress glenoid cavity
Fix scapula to thoracic wall

Question 5

Rhomboid minor slide 21

Answer 5

Proximal attachment
Nuchal ligament
Spinous processes of C7 & T1 vertebrae
Distal attachment
Smooth triangular area at medial end of scapular spine

Innervation
Dorsal scapular nerve
(C4, C5)

Main actions
Retracts scapula and rotate it to depress glenoid cavity
Fix scapula to thoracic wall

Question 6

Serratus posterior superior

Answer 6

Superior
attachment
Nuchal ligament, spinous processes of C7 to T3
Inferior
attachment
Superior borders of
2nd to 4th ribs

Innervation

2nd to 5th intercostal nerves

Main actions

Proprioception

(Elevates ribs)

Question 7

Serratus posterior inferior slide 26

Answer 7

Superior attachment
Spinous processes
of T11 to L2
Inferior
attachment
Inferior borders of 8th to 12th ribs near their angles

Innervation
Anterior rami to T9 to T12 thoracic spinal nerves

Main actions

Proprioception

(Depress ribs)

Question 8

Label cadaver pic on slide 27

Answer 8

Yep

Question 9

1. The thoracodorsal nerve innervates which extrinsic back muscle?
2. Which nerve provides motor innervation to trapezius?
3. What is the main action of levator scapulae?
4. Which nerve spinal cord segments contribute to the dorsal scapular nerve?
5. What is the main action of the serratus posterior muscles?

Answer 9

1. The thoracodorsal nerve innervates which extrinsic back muscle? Latissimus dorsi
2. Which nerve provides motor innervation to trapezius? Spinal accessory nerve CN XI
3. What is the main action of levator scapulae? Elevates the scapula! 
4. Which nerve spinal cord segments contribute to the dorsal scapular nerve? C4, C5
5. What is the main action of the serratus posterior muscles? Proprioception!