The Thoracic Wall

Question 1

Describe the arrangement of the ribs.

Answer 1

Ribs 1-7 are true ribs - their costal cartilages articulate directly with the sternum
Ribs 8-10 are false ribs - their costal cartilages join onto the costal cartilages of the ribs above them before joining the sternum
Ribs 11 + 12 are floating ribs - they have costal cartilage but it doesn’t articulate with anything. There is not connection with the sternum.

Question 2

What do the ribs articulate with?

Answer 2

The costal cartilage anteriorly and the vertebral column via the head and tubercle of the rib

Question 3

Where does the first rib attach medially?

Answer 3

Manubrium

• superior to manubriosternal joint (sternal angle)
• just inferior to the clavicle articular site
• just inferior to the sternoclavicular joint

Question 4

What defines the thoracic inlet (superior thoracic aperture)?

Answer 4

1st rib and costal cartilage, 1st thoracic vertebra (T1) and the manubrium

Question 5

Describe the structure of the diaphragm.

Answer 5

The diaphragm has a central tendon and it is attached to the costal margin and vertebrae.

Question 6

What is the secondary role of the intercostal muscles?

Answer 6

They stiffen the chest wall to improve the efficiency of breathing movements.

Question 7

How are the intercostal muscles arranged? State the directions of the muscle fibres.

Answer 7

External intercostal - inferomedially (hands in pockets) - at the costo-chondrial junction it is replaced by an anterior intercostal membrane
Internal Intercostal - perpendicular to the external intercostals - replaced by a posterior intercostal membrane posteriorly
Innermost intercostal - same orientation as internal IC

Question 8

How many intercostal nerves are there?

Answer 8

11 pairs (T1 - T11) and a subcostal nerve (T12) 
They involve a mix of motor and sensory nerves and supply the intercostal spaces

Question 9

Describe the branching of intercostal nerves.

Answer 9

There is a lateral cutaneous branch (which splits into an anterior branch and a posterior branch)
There is an anterior cutaneous branch (which splits into a medial branch and a lateral branch)

Question 10

Where are the intercostal neurovascular bundles found?

Answer 10

Internal intercostal and innermost intercostal

Just below the bottom edge of a rib

Question 11

What implications does this have for putting a needle or chest drain through the thoracic wall?

Answer 11

As the neurovascular bundle is just below the bottom edge of a rib, you would want to insert the needle just above the superior edge of a rib to avoid piercing the neurovascular bundle

Question 12

What are the borders for the safe area for inserting a chest drain?

Answer 12

5th intercostal space, anterior to the mid-axillary line
Anterior border of the latissimus dorsi
Lateral border of pectoralis major
A line superior to the horizontal level of the nipple
Apex below the axilla

Question 13

What major artery do the intercostal arteries anastomose (join) with?

Answer 13

Internal thoracic arteries

Question 14

What do the internal thoracic arteries branch from?

Answer 14

Right and left subclavian arteries

Question 15

Which rib articulates with the sternum at the sternal angle?

Answer 15

Rib 2

Question 16

What are the contents of the thoracic inlet (superior thoracic aperture)?

Answer 16

All the great vessels heading towards the neck and upper limbs, oesophagus, trachea, nerves and lymphatics

Question 17

What are the external intercostal muscles replaced with at the costo-chondral (rib-cartillage) junction?

Answer 17

Anterior intercostal membrane

Question 18

What are the internal intercostal muscles replaced with posteriorly?

Answer 18

Membrane

Question 19

What is the term that collectively describes the intercostal nerve, intercostal artery and intercostal vein which run above the ribs rather in within the groove (superior part of ribs)?

Answer 19

Collateral branch

Question 20

Which order do the intercostal arteries, veins and nerves run within the groove on the inferior surface of the ribs?

Answer 20

Vein, artery nerve

Question 21

What does the term fascia mean? Where are they found within the thorax structure?

Answer 21

Fibrous tissue which surrounds organs / muscles
Found as
a) ENDOTHORACIC FASCIA = between innermost muscle and parietal pleura
b) SUPERFICIAL FASCIA = between IC muscles and subcutaneous fat

Question 22

What does the term anastomoses mean?

Answer 22

Joining of intercostal arteries

Question 23

Describe the joining of intercostal vessels and nerves

Answer 23

Intercostal arteries join at both the anterior (internal thoracic vessel) and posterior (posterior intercostal vessels) sides
Nerves however only join at the posterior surface (posterior ramps of spinal nerve)

Question 24

Which major vessel do the thoracic veins anastomose with?

Answer 24

Brachiocephalic vein

Question 25

What exactly is the mediastinum?

Answer 25

Space between the pleural cavities

Question 26

What are the contents of the mediastinum?

Answer 26

Heart (in pericardium)
Great vessels
Oesophagus
Trachea
THYMUS
Lymph nodes
Thoracic duct
Phrenic and vagus nerves