Thoracic Myology

Question 1

What are the intercostal muscles?

Answer 1

External and internal intercostal M

Innermost intercostal M

Question 2

Describe the external intercostal M

Answer 2

11 pairs
Anteriorly muscle fibers replaced by the external intercostal membrane which overlies the internal intercostal M
Inferiorly is continuous with the EOM

Question 3

What is the origin and insertion for the intercostal muscles?

Answer 3

O: Inferior border of ribs
I: superior border of rib below

Question 4

What innervates all intercostal muscles?

Answer 4

Intercostal N

Question 5

What is the action of the external intercostal M?

Answer 5

Elevate ribs

Question 6

What is the action of the internal intercostal M?

Answer 6

Depress ribs (interchondral part elevates ribs)

Question 7

What is the action of the innermost intercostal M?

Answer 7

Most likely the same as the internal intercostal

Question 8

Describe the internal intercostal M

Answer 8

11 pair
Posteriorly muscle fibers are replaced by the internal intercostal membrane whcih is visible in the posterior mediastinum immediately lateral to the vertebral column
Inferiorly the internal intercostal M is continuous with the IOM

Question 9

Describe the innermost intercostal M

Answer 9

11 pair
The deepest fibers of the internal intercostal M
Separated from the internal intercostal M by the intercostal N and vessels

Question 10

What is a thoracentesis?

Answer 10

Insertion of a hypodermic needle through the intercostal musculature between ribs to obtain a fluid sample or drain small amounts of fluid from the pleural cavity
The needle is inserted b/w ribs inferior to the internal neurovascular bundle but superior to the collateral branches

Question 11

Describe insertion of a chest tube

Answer 11

Insertion of a tube to remove large amounts of air, fluid, blood or pus from the pleural cavity
Tube is typically inserted in the 5th or 6th intercostal space

Question 12

What is a thoroscopy?

Answer 12

Insertion of a thoroscope into the pleural cavity through small incisions for visualizing and biopsy Ig the space inside the pleural cavity

Question 13

What are the internal thoracic wall muscles?

Answer 13

Transverse thoracic and subcostal M

Question 14

What is the origin and insertion of the transverse thoracic M?

Answer 14

O: posterior surface of the lower part of the sternal body and xiphoid process
I: internal surface of the 2nd-6th costal cartilages

Question 15

What is the action of the transverse thoracic M?

Answer 15

Depress ribs

Question 16

What innervates the internal thoracic wall muscles?

Answer 16

Intercostal N

Question 17

Describe the subcostal M

Answer 17

Typically appears over the innermost intercostal M on the internal surface of the posterior thoracic wall near the angles of the ribs

Question 18

What is the origin and insertion of the subcostal M?

Answer 18

O: inferior border of rib
I: superior border of rib (1 to 2 rib segments)

Question 19

What is the action of the subcostal M?

Answer 19

Probably act as the internal intercostal M