Thorax:Intercostal Space

Question 1

What are the three main intercostal muscles we have?

Answer 1

External intercostal muscle (superficial)
Internal intercostal muscle (intermediate)
Innermost intercostal muscle (deep)

Question 2

What is the superior attachment, inferior attachment, innervation and action of the external intercostal muscle?

Answer 2

SUP. ATTACHMENT
-Inferior margin of the rib above.
INF. ATTACHMENT
-Superior margin of the rib below.
INNERVATION
-Intercostal nerves (T1-T11)
ACTION
-Assist during inspiration.
-Pull the ribs superiorly.

Question 3

What is the superior attachment, inferior attachment, innervation and action of the internal intercostal muscle?

Answer 3

SUP. ATTACHMENT
-Lateral edge of the costal groove of the rib above.
INF. ATTACHMENT
-Superior margin of the rib below.
INNERVATION
-Intercostal nerves (T1-T11)
ACTION
-Mostly active during expiration.
-Moves ribs inferiorly.

Question 4

What is the superior attachment, inferior attachment, innervation and action of the innermost intercostal muscle?

Answer 4

SUP. ATTACHMENT
-Medial edge of costal groove of rib above.
INF. ATTACHMENT
-Superior margin of the rib below.
INNERVATION
-Intercostal nerves (T1-T11)
ACTION
-Also assist during expiration.

Question 5

What is the superior attachment, inferior attachment, innervation and action of the subcostales muscles?

Answer 5

SUP. ATTACHMENT
-Internal surface of lower ribs.
INF. ATTACHMENT
-Internal surface of 2nd or 3rd rib below.
INNERVATION
-Related intercostal nerves
ACTION
-Depresses ribs.

Question 6

What is the superior attachment, inferior attachment, innervation and action of the transversus thoracis muscle?

Answer 6

SUP. ATTACHMENT
-Inferior margin and internal surfaces of costal cartilages of ribs 2-6.
INFERIOR ATTACHMENT
-Body and xiphoid process of sternum.
-Costal cartilages 4-7.
INNERVATION
-Related intercostal nerves
ACTION
-Depresses the costal cartilages.

Question 7

What makes up the intercostal neurovascular bundle?

Answer 7

Intercostal vein
Intercostal artery
Intercostal nerve

Question 8

Where do the posterior intercostal veins drain into?

Answer 8

The azygos system of veins

Question 9

Where do the anterior intercostal veins drain into?

Answer 9

Internal thoracic vein which ultimately drains into the brachiocephalic vein.

Question 10

Where does the first posterior intercostal bein drain into?

Answer 10

Brachiocephalic vein

Question 11

On the left side where does the 2nd, 3rd and (sometimes) 4th PIV drain into?

Answer 11

Left superior intercostal veins which ultimately drain into the left brachiocephalic vein.

Question 12

On the right side, where do the 2nd, 3rd and (sometimes) 4th post. intercostal veins drain into?

Answer 12

The right superior intercostal veins which ultimately drain into the azygos vein.

Question 13

On the left side where do the 4-8th and 9th-11th PIV drain into?

Answer 13

4th-8th:Accessory hemi-azygos vein
9th-11th: Hemi-azygos vein

Question 14

On the right side where do the 4-11 PIV drain into?

Answer 14

Azygos vein

Question 15

Where do the 1-6 AIV drain into?

Answer 15

Internal thoracic vein

Question 16

Where do the 7-9 AIV drain into?

Answer 16

Musculophrenic vein

Question 17

Where does the … posterior intercostal arteries arise from?
1. 1st and 2nd
2. 3-12

Answer 17

1. Subclavian artery, costocervical artery, supreme intercostal artery.
2. Descending thoracic aorta

Question 18

When does the internal thoracic artery terminates, and which structures does it terminate into?

Answer 18

At the 6th intercostal space.
Terminates into the musculophrenic artery and superior epigastric artery

Question 19

The upper 6 intercostal spaces of the AIA are supplied by which artery?

Answer 19

The internal thoracic artery

Question 20

The lower 3 intercostal spaces of the AIA are supplied by which artery?

Answer 20

Musculophrenic artery

Question 21

Main innervation of the thoracic wall?

Answer 21

Anterior rami of T1-T11 spinal nerves

Question 22

Functions of the intercostal nerves (3)

Answer 22

Carry:
-Somatic motor innervation to the thoracic muscles.
-Somatic sensory innervation from skin to parietal pleura.
-Postganglionic symphathetic fibers to periphery.

Question 23

Branches of the intercostal nerves (4)

Answer 23

Small collateral branch
Lateral cutaneous branch
Posterior cutaneous branch
Anterior cutaneous branch

Question 24

Explain the lymphatic drainage of the intercostal space. (3)

Answer 24

There are three nodes:
Parasternal nodes: associated with the internal thoracic arteries.
Diaphragmatic nodes: associated with the diaphragm.
Intercostal nodes: associated with the head and neck of ribs.