1.1 - 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 - just inferior to the sternoclavicular joint

Question 4

Which rib articulates with the sternum at the sternal angle?

Answer 4

Rib 2

Question 5

What defines the thoracic inlet (superior thoracic aperture)?

Answer 5

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

Question 6

Describe the structure of the diaphragm.

Answer 6

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

Question 7

What is the role of the intercostal muscles?

Answer 7

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

Question 8

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

Answer 8

External intercostal - inferomedially (like 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

Question 9

How many intercostal nerves are there?

Answer 9

11 and 1 subcostal nerve. They involve a mix of motor and sensory nerves and supply the intercostal spaces

Question 10

Describe the branching of intercostal nerves.

Answer 10

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 11

Where are the intercostal neurovascular bundles found?

Answer 11

Internal intercostal and innermost intercostal

Just below the bottom edge of a rib

Question 12

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

Answer 12

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 13

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

Answer 13

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

In general - 4th intercostal space, anterior to the mid-axillary line

Question 14

What major artery do the intercostal arteries anastomose with?

Answer 14

Internal thoracic

Question 15

What do the internal thoracic arteries branch from?

Answer 15

Right and left subclavian arteries

Question 16

What does the symphysis between vertebral bodies consist of?

Answer 16

Hyaline cartilage + intervertebral disc

Question 17

What are the two parts of the intervertebral disc?

Answer 17

Anulus fibrosus (collagen to limit rotation). 
Nucleus pulposus (absorb compression)

Question 18

Describe what can happen in disc herniation?

Answer 18

Degenerative changes in the anulus fibrosus can lead to herniation of the nucleus pulposus. Posterolateral
herniation can impinge on the roots of a spinal nerve in the intervertebral foramen.

Question 19

What are the two heads of the pectoralis major? What is its function and where does it insert?

Answer 19

Heads - Clavicular head and sternocostal head.

Insertion - Intertubercular sulcus of the humerus

Function:Adduction

Medial rotation

Flexion of humerus at the shoulder joint