3 Extrinsic Muscles of Back: Intermediate Layers

Question 1

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2

Answer 1

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle

Question 2

Extrinsic Muscles of Back: Intermediate Layers

Identify 5 - 6

Answer 2

5. Spinalis thoracis muscle
6. Iliocostalis thoracis muscle (retracted)

Question 3

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2

→ Origin?

Answer 3

1. Serratus posterior superior muscle

→ attaches to the lower extent of the ligamentum nuchae and the spinous processes of the C7-T3 vertebrae
2. Serratus posterior inferior muscle

Question 4

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2. Origin?

Answer 4

1. Serratus posterior superior muscle → attaches to the lower extent of the ligamentum nuchae and the spinous processes of the C7-T3 vertebrae
2. Serratus posterior inferior muscle → attaches to the spinous processes of the T11-L2 vertebrae and their supraspinous ligaments.

Question 5

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2

→ Insertion?

Answer 5

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle

→ RIBS

Question 6

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2. Action

Answer 6

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle

Action:

• The serratus posterior superior elevates the ribs
• The serratus posterior inferior pulls the ribs outward and downward, counteracting the inward pull of the diaphragm.

Question 7

Extrinsic Muscles of Back: Intermediate Layers

Identify 1 - 2. Nerve

Answer 7

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle

Innervation

• The serratus posterior superior is innervated by the anterior rami of the T1-T4 spinal nerves.
• The serratus posterior inferior is supplied by the anterior rami of the T9-T12 spinal nerves

Question 8

Extrinsic Muscles of Back: Intermediate Layers

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle

→ These 2 muscles have attachments to the ribs, are considered muscles of the thoracic wall (can be lumped into extrinsic back muscles), and act on the ribs during ____.

Answer 8

respiration

Question 9

Extrinsic Muscles of Back: Intermediate Layers

IDENFTIY 3 - 4

Answer 9

3. Iliocostalis lumborum muscle
4. Longissimus thoracis muscle

Question 10

Extrinsic Muscles of Back: Intermediate Layers

What are accessory muscles of respiration?

Answer 10

1. Serratus posterior superior muscle
2. Serratus posterior inferior muscle