Thoracic Wall

Question 1

What are the true ribs, false ribs, and floating ribs?

Answer 1

True ribs: 1-7

False ribs: 8-12

Floating ribs: 11-12 (in abdominal muscles)

Question 2

What ribs are not palpable?

Answer 2

1, 11, 12

Question 3

What intercostal space is located at the nipple?

Answer 3

4

Question 4

What are the three layers of intercostal muscles?

Answer 4

External, Internal, Innermost

Question 5

What is the function of the external intercostal muscles?

Answer 5

Most active during inspiration, moves ribs superiorly

Question 6

What is the function of the internal intercostal muscles?

Answer 6

Most active during expiration, moves ribs inferiorly

Question 7

What is the function of the innermost intercostal muscles?

Answer 7

Acts with internal intercostals

Question 8

What are the contents of each intercostal space?

Answer 8

Three layers of intercostal muscles

Intercostal neurovascular supply

Question 9

What is the external intercostal membrane?

Answer 9

Thin layer of connective tissue aponeurosis that replaces the external intercostal muscles in the anterior part of each intercostal space adjacent to the sternum

Question 10

What is the internal intercostal membrane?

Answer 10

Thin connective tissue aponeurosis that replaces the internal intercostal muscles in the posterior intercostal space adjacent to the vertebral columns

Question 11

What are the transversus thoracis muslces?

Answer 11

Located on deep surface of anterior thoracic wall, deep to internal thoracic vessels

Attaches to lower sternum and ribs 3-6

Depresses costal cartilage

Question 12

What are the subcostal muscles?

Answer 12

Located at lower regions of posterior thoracic wall

Depresses ribs

May span multiple ribs

Question 13

What is the intercostal neurovascular bundle?

Answer 13

Located between internal and innermost muscles at the inferior border of the rib in the costal groove

Order of structures superior to inferior: VAN

Vein ->artery->nerve (all intercostal)

Question 14

Where is a thoracostomy performed and why?

Answer 14

Directly above the rib at the 4th or 5th intercostal space

To avoid the neurovascular bundle

Question 15

What are the three movements of the thoracic wall during inspiration?

Answer 15

Vertical diameter - contraction of the diagphragm

Anteroposterior diameter - intercostal muscles

Transverse diameter - intercostal muscles

Question 16

Describe the posterior intercostal arteries

Answer 16

Branch from the aorta (except 1 and 2)

Supply each intercostal space

Larger than anterior intercostal arteries

Question 17

Describe the anterior intercostal arteries

Answer 17

Upper 6 originate from the internal thoracic artery

7-9 originate from the musculophrenic artery

There are none in the 10th and 11th spaces

Question 18

Where do the 1st and 2nd intercostal arteries arise from?

Answer 18

Superior intercostal artery, a branch of the costocervical trunk of the subclavian

Question 19

Describe the internal thoracic artery

Answer 19

Located parasternally, between the internal intercostal and transversus thoracis muscles

Divides into musculophrenic and superior epigastric arteries at the 6th intercostal space

Question 20

What is the musculophrenic artery?

Answer 20

Terminal artery that follows the costal margin and supplies the anterior intercostal arteries of 7-9 and adjacent diaphragm

Question 21

What is the superior epigastric artery?

Answer 21

Supplies the anterior abdominal wall

Travels through the sternocostal hiatus (gap in diaphragm)

Question 22

Where do the posterior and anterior intercostal veins drain?

Answer 22

Posterior - into azygous vein on the right side, hemiazygous and accessory hemiazygous veins on the left side

Anterior - internal thoracic and musculophrenic veins

Question 23

Where do the intercostal nerves originate?

Answer 23

Ventral rami of thoracic spinal nerves

Question 24

What do internal costal nerves carry?

Answer 24

Somatic motor innervation to thoracic wall muscles

Somatic sensory innervation for skin and parietal pleura

Posganglionic sympathetic fibers to the periphery