2.2 Muscles of the Anterior Thoracic Wall

Question 1

Identify the External intercostals, their attachments/function, and neurovasculature.

Answer 1

• Origin: lower aspect of one rib
• Insert: Upper aspect of next rib
• Function: raise ribs during inspiration; support intercostal spaces and stabilize chest wall
• Innervation: 1st-11th intercostal nerves
• Blood flow from intercostal artery

Question 2

Identify the Internal intercostals and innermost intercostals, their attachments/function, and neurovasculature.

Answer 2

• Origin: upper aspect of one rib
• Insertion: lower aspect of next rib
• Function: lower ribs during expiration; support intercostal space and stabilize chest wall
• Innervation: 1st-11th intercostal nerves
• Blood flow from intercostal artery

Question 3

Identify the Transversus thoraces, their attachments/function, and neurovasculature.

Answer 3

• origin: inner surface of body and xiphoid process of sternum
• insertion: inner surface of ribs 2-6 (and costal cartilage at these levels)
• Typically skip a rib between origin and insertion
• Innervation: 2nd to 6th intercostal nerves
• Internal thoracic artery
• Function: Compress thorax for forced expiration

Question 4

Identify the Subcostals, their attachments/function, and neurovasculature.

Answer 4

Origin: angle of rib
Insertion: angle of rib 2-3 ribs above
Innervation: Intercostal nerve
Blood flow: Intercostal artery
Function: Compress intercostal spaces

Question 5

Identify the Endothoracic fascia. Between what layers does this reside/what is its function?

Answer 5

Attaches parietal pleura to body wall

Question 6

Identify the Internal thoracic artery and vein.
From what artery does it branch?
Into what vein does it drain?

Answer 6

Run down inside wall of rib cage on either side, medially
Internal thoracic arteries branch from the left and right subclavian arteries.
Internal thoracic veins drain into the left and right brachiocephalic veins.

Question 7

Identify the anterior intercostal arteries and veins. From where do these branch.

Answer 7

Branch from internal thoracic artery/vein

Question 8

Identify where the Anterior perforating artery and vein would be. From where does this branch?

Answer 8

Located in the skin overlying pectoralis major.

Branch/Drain from the internal thoracic artery and vein

Question 9

Identify the External intercostal membrane

Answer 9

The muscular portion of an external intercostal is replaced by the external intercostal membrane at the costochondral junction.

Question 10

Costochondral junction

Answer 10

Cartilage between ribs and sternum.