The Thoracic Wall Flashcards
Describe the arrangement of the ribs.
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.
What do the ribs articulate with?
The costal cartilage anteriorly and the vertebral column via the head and tubercle of the rib
Where does the first rib attach medially?
Manubrium - just inferior to the sternoclavicular joint
What defines the thoracic inlet (superior thoracic aperture)?
1st rib and costal cartilage, 1st thoracic vertebra (T1) and the manubrium
Describe the structure of the diaphragm.
The diaphragm has a central tendon and it is attached to the costal margin and vertebrae.
What is the role of the intercostal muscles?
They stiffen the chest wall to improve the efficiency of breathing movements.
How are the intercostal muscles arranged? State the directions of the muscle fibres.
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
How many intercostal nerves are there?
11 pairs (T1 - T11) and a subcostal nerve (T12) They involve a mix of motor and sensory nerves and supply the intercostal spaces
Describe the branching of intercostal nerves.
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)
Where are the intercostal neurovascular bundles found?
Internal intercostal and innermost intercostal
Just below the bottom edge of a rib
What implications does this have for putting a needle or chest drain through the thoracic wall?
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
What are the borders for the safe area for inserting a chest drain?
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
What major artery do the intercostal arteries anastomose with?
Internal thoracic
What do the internal thoracic arteries branch from?
Right and left subclavian arteries
Which rib articulates with the sternum at the sternal angle?
Rib 2
