3.2 Muscles of the Posterior Thoracic Wall

Question 1

Identify the Innermost intercostal muscles, their attachment/function, and neurovasculature.

Answer 1

1. Originate from the lower margin of one rib and insert onto the upper margin of the next rib. They course obliquely forward and upward from the costal angle to the sternum.
2. Innervation: 1st to 11th intercostal nerves
3. Function: lower the ribs during expiration, to support the intercostal spaces, and to stabilize the chest wall.
4. Intercostal artery

Question 2

Identify the Subcostal muscles, their attachment/function, and neurovasculature.

Answer 2

1. Originate from lower margin of the lower ribs and attach to the inner surface 2-3 ribs below.
2. Innervated by 2nd-7th intercostal nerves.
3. Function: help to raise the ribs during inhalation.
4. Intercostal artery

Question 3

Identify the Intercostal nerves. From where do they originate.

Answer 3

A distributed ventral (anterior) ramus of a thoracic spinal nerve

Question 4

Identify the Posterior intercostal arteries and veins. From where do they branch/drain. What is their function?

Answer 4

1. Arteries arise from thoracic aorta.
2. Veins drain into azygous system
3. provide vasculature for intercostal muscles

Question 5

Identify the Sympathetic trunk. What spinal levels does this span and what type of innervation does it provide?

Answer 5

Runs longitudinally along the posterior thoracic wall. (T1-L2).
Sympathetic innervation of the ANS.

Question 6

Identify the Sympathetic ganglia

Answer 6

Bulge in sympathetic trunk; ganglion

Question 7

Identify the Gray rami communicants and their function

Answer 7

Branch from sympathetic trunk –> spinal nerve.

Question 8

Identify the White rami communicants and their function.

Answer 8

The preganglionic sympathetic outflow nerve tract from the spinal cord

Question 9

Identify and describe the Splanchnic nerves

Answer 9

1. Lateral branches off the sympathetic trunk are rami communicantes. Medial branches off the trunk are splanchnic nerves.
2. The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs), carrying fibers of the autonomic nervous system (visceral efferent fibers) as well as sensory fibers from the organs (visceral afferent fibers).

Question 10

Identify the Costal pleura

Answer 10

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Question 11

Identify the Accessory hemiazygos vein. What are its main tributaries and what vein does it join prior to draining into the SVC?

Answer 11

1. Receives the posterior intercostal veins from the superior aspect of the posterior thoracic wall on the left. Inferiorly it crosses the midline to join the azygos vein around T8.

Question 12

Identify the Hemiazygos vein. What are its main tributaries and what vein does it join prior to draining into the SVC?

Answer 12

1. Receives the posterior intercostal veins from the inferior aspect of the posterior thoracic wall on the left. Superiorly it crosses the midline to join the azygos vein around T9.

Question 13

Identify the Azygos vein. Into what vein does this drain?

Answer 13

A large vein on the right side of the posterior thorax. Drains into the SVC.