Deep Back

Question 1

What is the innervation to deep back muscles? Are these muscles intrinsic or extrinsic? What is the overal function of these muscles?

Answer 1

• Posterior Rami of Spinal Nerves
• Intrinsic muscles
• Move vertebral column

Question 2

What are the three component layers of the deep (intrinsic) back muscles?

Answer 2

1. Most Superficial: Splenius
2. Intermediate: Erector Spinae
3. Deepest: Transversospinalis

Muscles are covered by thoracolumbar fascia (deep fascia)

Question 3

What muscles comprise the most superficial of the deep back muscles?

Answer 3

1. Splenius Capitis
2. Splenius Cervicis

Question 4

Answer 4

Splenius Capitis

Deep to serratus posterior superior

Origin:

• Ligamentum Nuchae
• Spinous Processes C7-T3

Insertion:

• Mastoid Process
• Superior Nuchal Line
• Head

Innervation:

• Posterior Rami of Spinal nn.

Action:

• Bilaterally: extend neck
• Unilaterally: flex/rotate head to same side

Blood Supply:

• Occipital a.

Question 5

Answer 5

Splenius Cervicis

Deep to serratus posterior superior

Origin:

• Spinous processes T3-T6

Insertion:

• Transverse processes C1-C2
• Neck

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extend the neck
• Unilaterally: flex/rotate head to same side

Blood Supply:

• Occipital a.

Question 6

What muscles comprise the intermediate deep back muscles?

Answer 6

Erector Spinae (Help stand upright)

Comprised of:

1. Iliocostalis
2. Longissimus
3. Spinalis

“I love [your favorite S-word]”

Question 7

Answer 7

Iliocostalis

Deep to serratus posterior inferior

Most lateral of erector spinae mm.

Attachments:

• Angles of Ribs

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilateral: extends spine
• Unilateral: bends spine lateral to same side

Question 8

Answer 8

Longissimus

Deep to serratus posterior inferior

Middle of erector spinae mm.

Attachments:

• Typically originate/insert on tranverse processes of vertebrae

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extends head and spine
• Unilaterally: flexes/rotates head/spine to same side

Question 9

Answer 9

Spinalis

Deep to serratus posterior inferior

Most medial of erector spinae mm.

Attachments:

• Originate/insert on spinous processes

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: Extends cervical and thoracic spine
• Unilaterally: Bends cervical/thoracic spine to same side

Question 10

What muscles comprise the deepest of the deep back muscles? What direction do these fibers run?

Answer 10

Transversospinalis mm.

Run superomedially

Include:

• Multifidus
• Semispinalis
• Rotatores

Function:

• Stabilize Spine

Question 11

Answer 11

Semispinalis Capitis

Deep to the splenius mm.

Attachments:

• See picture (not emphasized in class)

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extends thoracic/cervical spine
• Unilaterally: bends head/cervical/thoracic spine to same side

Question 12

What nerve passes through semispinalis capitis?

Answer 12

Greater Occipital Nerve

Question 13

Answer 13

Semispinalis Cervicis

Deep to semispinalis capitis

Attachments:

• See image (not emphasized in class)

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extends thoracic/cervical spine
• Unilaterally: bends head/cervical/thoracic spine to same side

Question 14

Answer 14

Multifidus

Attachments:

• Between transverse and spinous processes, skipping two to four vertebrae

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extend spine
• Unilaterally: flex spine to same side

Question 15

Answer 15

Rotatores

Attachments:

• Between transverse and spinous process of adjacent (or, skipping one vertebra)

Innervation:

• Posterior rami of spinal nn.

Action:

• Bilaterally: extends thoracic spine
• Unilaterally: rotates spine to opposite side

Question 16

Posterior Rami of Spinal Nerves

Answer 16

• Innervate skin of the back and deep back muscles
  
  • ​Cutaneous innervation is segmental (form dermatomes)

Question 17

Describe blood supply to back

Answer 17

• Segmental from posterior intercostal aa.