Chest Wall

Question 1

What are the muscles of the thoracic wall?

Answer 1

pec major/minor, serratus anterior, intercostal muscles, subcostalis, transverse thoracis

Question 2

Where are the intercostal muscles located ?

Answer 2

between the ribs, and they do not cross the ribs

Question 3

Which intercostal muscles can you see on the anterior wall of the chest?

Answer 3

External (stops close to the sternum) and the Internal (at the sternum)

Question 4

What intercostal muscle can you see on the internal chest wall?

Answer 4

innermost and internal

Question 5

What is the fiber direction of the external intercostal muscles?

Answer 5

inferomedially (hands in pocket)

Question 6

What is the fiber direction of the internal and innermost intercostal muscles?

Answer 6

superomedially

Question 7

What is the function of the external intercostals?

Answer 7

Because they travel inferomedially, when they contract they elevate the ribs and expand the chest. This means that they assist in regular and forced inhalation

Question 8

What is the function of the internal and innermost intercostal muscles?

Answer 8

Because they travel superomedially, when they contract, they depress the ribs, so they assist in forced exhalation.

Question 9

Why does the internal and innermost intercostal muscles do not assist in regular exhalation?

Answer 9

Regular exhalation is a passive movement and it does not require a muscle to do so.

Question 10

What is the supply of the intercostals and where do they travel?

Answer 10

The intercostal supply of the intercostal muscles is the VAN, and they travel in the costal ridge of the ribs, which is located on the bottom portion of the ridge. They also have collaterol branches of the VAN on the superior side.

Question 11

Where is the transverse thoracis muscle located and what is its function?

Answer 11

It is located on the anterior chest wall, on the interior side. It crosses over two rib spaces, and its function is to assist in expiration.

Question 12

What is the function of the subcostalis muscle? Where is it located?

Answer 12

It is located on the posterior chest wall, on the interior side, and it crosses over 2 rib spaces and its function is the elevate the ribs

Question 13

How many intercostal spaces are there? How are they numbered?

Answer 13

There are 11 intercostal spaces and they are numbered based on the rib above them. There are 12 ribs, 11 intercostal spaces, and 1 subcostal space below rib 12

Question 14

What is the arterial supply of the intercostal spaces and why the difference between some of them?

Answer 14

Spaces 1-9 have 3 arterial supplies: 1 Large posterior intercostal a and 2 (a pair) of anterior intercostal arteries. Spaces 10-11 are only supplied by the posterior intercostal a. This is because those ribs do not come anteriorly to the sternum and thus do not require an anterior supply

Question 15

What are the components of the VAN? And where does the VAN travel?

Answer 15

Intercostal vein, artery, and nerve. It travels in the costal ridge between the internal and innermost intercostal muscles.

Question 16

Describe the origin/branching of the anterior intercostal arteries.

Answer 16

The anterior intercostal arteries only supply Intercostal Spaces 1-9. The subclavian artery gives off the internal thoracic artery, which supplies intercostal spaces 1-6. Then the internal thoracic artery splits to the musculophrenic artery, which supplies 7-9. The internal thoracic also splits into the superior epigastric artery, which is not used to give off the anterior intercostal arteries.

Question 17

Describe the origin/branching of the posterior intercostal arteries.

Answer 17

The posterior arteries supply all 11 intercostal spaces. The superior (supreme) intercostal a, which is a branch of the subclavian artery, and it supplies the 1st and 2nd intercostal spaces. The thoracic aorta supplies the rest of the intercostal spaces (3-11), as well as the subcostal space for rib 12 (which does not have an intercostal space)

Question 18

Describe the venous drainage of the anterior intercostal veins.

Answer 18

Anterior intercostal veins –> internal thoracic vein –> brachiocephalic v –> superior vena cava

Question 19

Describe the venous drainage of the posterior intercostal veins. (only the 1st three intercostal spaces)

Answer 19

1. 2nd/3rd post. intercostal veins –> 1st post. intercostal veins –> brachiocephalic vein –> superior vena cava

Question 20

Describe the venous drainage of the posterior intercostal veins (everything except the first three intercostal spaces)

Answer 20

1. Upper Left post. intercostal veins –> accessory hemizygous v. –> azygous vein –> superior vena cava
2. Lower Left post. intercostal veins –> hemizygous v. –> azygous v. –> superior vena cava
3. Right posterior intercostal veins –> azygous v. –> superior vena cava

Question 21

Describe the nerve supply of the intercostal spaces

Answer 21

11 intercostal nerves, which come off of the ventral rami of T1-T11.
1 subcostal nerve, which comes off of the ventral rami of T12

The ventral rami turns into the intercostal/subcostal nerves

Question 22

What is the clinical significance of the internal thoracic artery

Answer 22

In the event where you have blockage in your coronary arteries, a coronary artery bypass graft (CABG) can be performed, using the internal thoracic artery (which supplies the anterior intercostal arteries) to provide the arterial supply for the heart. This works because there is an anastamosis between the anterior/posterior intercostal arteries, so the CABG will not completely deprive the anterior intercostal spaces blood supply, because of the anastamosis.

Question 23

Arteries of the thoracic wall

Answer 23

subclavian artery –> internal thoracic artery (1-6) –> musclophrenic a (7-9) and superior epigastric (ANTERIOR)

superior thoracic artery –> posterior intercostal a (1-2) (POSTERIOR)

thoracic aorta –> posterior intercostal a (3-11)

Question 24

Explain the venous drainage of the posterior thoracic wall

Answer 24

Posterior:

1. 2/3 intercostal v. –> 1st intercostal v –> brachiocephalic v. –> superior vena cava
2. Upper left posterior intercostal v. –> accessory hemizygous v. –> azygous v. –> superior vena cava
3. Lower left posterior intercostal v. –> hemizygous v. –> azygous v –> superior vena cava
4. Right posterior intercostal v. –> azygous v. –> superior vena cava

Question 25

Explain the drainage system of the anterior thoracic wall

Answer 25

anterior intercostal v. –> internal thoracic v. –> brachiocephalic v. –> superior vena cava

Question 26

What forms the brachiocephalic vein

Answer 26

internal juggular v. and subclavian v.

Question 27

Explain the drainage of the azygous system

Answer 27

hemizygous v and accessory hemizygous–> azygous –> superior vena cava

Question 28

Three compartments of the thoracic cavity

Answer 28

1. Right pulmonary cavity: lung and plura
2. Left Pulmonary cavity: lung and plura
3. Mediastinum: heart/great vessels, trachea, esophogaus, thymus