Lecture 4: Back Myology

Question 1

What are the two Layer 1 muscles of the back and what are their innervations?

Answer 1

1. Trapezius M. (Spinal Accessory Nerve XI)

2. Latissimus Dorsi M. (Thoracodorsal N.)

Question 2

Trapezius M. action

Answer 2

• Whole muscle: rotate Glenoid Cavity superior/retract scapula
• upper fibers (elevate scapula), lower fibers (depress)
• laterally flex and rotate face away (unilateral)

Question 3

Latissimus Dorsi M. action

Answer 3

• extend, ADduct, medially rotate humerus

- rotate Glenoid Cavity inferiorly

Question 4

What are the 3 Layer 2 muscles of the back and what are their innervations?

Answer 4

1. Levator Scapulae
2. Rhomboid Minor
3. Rhomboid Major

innervation: Dorsal Scapular N.

Question 5

Rhomboid Minor and Major M. actions

Answer 5

• retract/elevate scapula

- rotate Glenoid Cavity Inferiorly

Question 6

Levator Scapulae M. action

Answer 6

• elevate scapula, Rotate Glenoid Cavity inferiorly

- [fixed scap] –> extend, laterally flex neck

Question 7

What are the 2 Layer 3 muscles of the back and what are their innervations?

Answer 7

1. Serratus Posterior Superior M. (Intercostal N.)

2. Serratus Posterior Inferior M. (T9-T12)

Question 8

Serratus Posterior Superior and Inferior M. actions

Answer 8

Superior: elevate ribs w/forced inspiration

Inferior: depress ribs w/forced expiration

Question 9

What are the 2 Layer 4 muscles of the back and what are their innervations?

Answer 9

1. Splenius Capitis M. (posterior rami)

2. Splenius Cervicis M. (posterior rami)

Question 10

Splenius Capitis and Splenius Cervicis M. actions

Answer 10

• extend neck (bilaterally)

- laterally flex and rotate face toward (unilaterally)

Question 11

What is the Layer 5 muscles and what is its innervation?

Answer 11

Erector Spinae Group (posterior rami)

Question 12

What are the 3 groups that make up Erector Spinae group, and what are the 3 divisions of each of those groups? (I Love Spaghetti)

Answer 12

1. Iliocostalis M. (lumborum, thoracis, cervicis)
2. Longissimus M. (thoracis, cervicis, capitis)
3. Spinalis (thoracis, cervicis, capitis)

Question 13

Back Sprain vs Back Strain

Answer 13

Sprain: injury to ligamentous attachments between bones (inadequate stretching)

Strain: excessive stretch/tearing of muscle fibers (overly strong muscle contraction)

Question 14

What are the 4 Layer 6 muscles of the back and what are their innervations/actions?

Answer 14

1. Rotatores Brevis (extend to adjacent spinal segment)
2. Rotatores Longus (extend 2 spinal segments)
3. Mutifidus M. (extend 3/4 spinal segments)
4. Semispinalis M. (extend 5/6 spinal segments)

innervation: posterior rami
action: extend spine, rotate spine away

Question 15

What are the 3 divisions of the semispinalis M. and what are their actions?

Answer 15

• thoracis, cervicis, capitis

action: extend spine (neck), rotate spine (face) away

Question 16

Interspinalis M. action and innervation

Answer 16

action: extend spine
innervation: posterior rami

Question 17

Intertransversarii M. action and innervation

Answer 17

action: laterally flex spine
innervation: anterior AND posterior rami

Question 18

Levator Costarum Longus and Brevis M. action and innervation

Answer 18

Longus: extend to 2nd rib inferior from origin
Brevis: extend to adjacent rib inferior from origin

action: elevate ribs
innervation: posterior rami

Question 19

What are the 4 Suboccipital Region muscles and what are their innervation?

Answer 19

1. Rectus Capitis Posterior Major M.
2. Rectus Capitis Posterior Minor M.
3. Obliquus Capitis Superior M.
4. Obliquus Capitis Inferior M.

innervation: Suboccipital N.

Question 20

Rectus Capitis Posterior Major M. action

Answer 20

extend head, rotate face toward

Question 21

Rectus Capitis Posterior Minor M. action

Answer 21

extend head

Question 22

Obliquus Capitis Superior M. action

Answer 22

extend, laterally flex neck

Question 23

Obliquus Capitis Inferior M. action

Answer 23

rotate face toward

Question 24

What are the two structures moving through the Suboccipital Triangle and what structure is present inferior to the Triangle?

Answer 24

• in triangle: Vertebral A. and Suboccipital N.

- below triangle: Greater Occipital N.