2. The Thoracic Wall Flashcards
Anterior (ventral)
Towards FRONT of body
Posterior (dorsal)
Towards BACK of body
Superior (cranial)
Towards HEAD
Inferior (caudal)
Towards FEET
Midline (median), mid-sagittal
Straight down middle, divides body into 2 equal sides
Medial
Towards the midline
Lateral
Away from the midline
Proximal
Towards body (when referring to a limb)
Distal
Away from body (when referring to a limb)
Superficial
Close to surface
Deep
Far from surface
Sagittal
Cuts through from front to back (vertical)
Frontal (coronal)
Cuts through from side to side
Horizontal (transverse or axial)
Cuts through horizontally to body
Number of thoracic vertebrae
12
Number of pairs of ribs
12
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: Lack anterior attachment (not connected to sternum)
What are articulations? Describe the articulations of the ribs
Joinings
All ribs articulate with vertebral column via head and tubercle
Most of the ribs articulate with costal cartilages
Tubercle
Sticks out of a bony structure, provides site of attachment for ligaments/ muscles
Facet
Place where bones join to other bones
Where is the ribcage wider?
Bottom
How do the ribs slope as they come to the anterior?
Ribs slope downwards as they come to the anterior
What are the 3 divisions of the sternum?
Manubrium
Body
Xiphoid
Where does the 1st rib attach medially?
Manubrium
just inferior to the sternoclavicular joint
Where does the 2nd rib attach medially?
Manubriosternal joint (STERNAL ANGLE)
Where do ribs 3 to 7 attach medially?
Sternum
Where do ribs 8 to 10 attach medially?
Costal cartilage above
What defines the thoracic inlet (superior thoracic aperture)?
1st pair of ribs
1st thoracic vertebra (T1)
Manubrium
Contents of thoracic inlet
Great vessels from heart emerging to supply head, neck and upper limb
Oesophagus, trachea, nerves and lymphatics descending
= Vulnerable area as not protected by a ‘bony cage’
Describe the structure of the diaphragm.
Has a flat central tendon with muscle radiating to costal margin and vertebrae.
What is the role of the intercostal muscles?
Stiffen the chest wall to improve the efficiency of breathing movements.
How does the diaphragm move in inspiration?
Dome flattens to increase vertical diameter of chest
Pulls costal margin up to increase transverse and antero-posterior diameters
How do the ribs move in inhalation?
Sternum moves out and up
Ribs swing out and up, “become more horizontal”
Dimensions of thoracic cavity increase antero-posteriorly and medio-laterally
How are the intercostal muscles arranged? State the directions of the muscle fibres.
External intercostal:
Inferomedially (like hands in pockets) from lower border of rib above to rib below
At the costo-chondrial junction it is replaced by an anterior intercostal membrane
Internal Intercostal:
Supromedially
Attachments begin anteriorly at the sternum
Perpendicular to external intercostals Replaced by a membrane posteriorly
Innermost intercostal:
Same orientation as internal
Where is the neuromuscular bundle? Describe the structure
Just below rib Between internal and innermost intercostals Vein most superior Artery in middle Nerve below
How many intercostal nerves are there?
11 pairs (T1 - T11)
and a subcostal nerve (T12)
A mix of motor and sensory nerves
Supply the intercostal spaces
Describe the branching of intercostal nerves.
Lateral cutaneous branch (which splits into an anterior and a posterior branch)
Anterior cutaneous branch (which splits into a medial and a lateral branch)
Is the neuromuscular bundle protected?
Bottom of rib is like a collar, protects blood vessels but nerve hangs just below
What implications does the location of the neuromuscular bundle 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: 5th intercostal space, anterior to the mid-axillary line
What is the difference in anastomoses between the nerves and blood vessels in the neuromuscular bundle?
Nerves only emerge from spinal cord and have to make way to anterior
Blood vessels come from tributaries of major vessels anterior and posterior
Anastomosis
Region where arteries/ veins from different directions (front and back) are in close proximity supply same area of tissue
What do the internal thoracic arteries branch from?
Right and left subclavian arteries
What major artery do the intercostal arteries anastomose with?
Internal thoracic
What is the space between the pleural cavities of each lung called?
Mediastinum
To what height do the lungs extend to?
2-3cm above the clavicle
