Anterior and Superior Mediastinum Flashcards
What are the boundaries of the Anterior Mediastinum?
between the sternum and the pericardium
What are the boundaries of the Superior mediastinum?
- between the thoracic inlet and the sternal angle at level T4/5
- posterior to the manubrium of the sternum
- anterior to T1- T4
- oblique from manubrium upwards to T1
Which structure lies in the anterior mediastinum?
thymus
Where is the thymus situated?
from the jugular notch to the 4th costal cartilage
What is its structure and function?
- bi-lobed
- T lymphocytes and recognition of self
What are the anatomical relations of the thymus?
- SVC and Aorta
- L+R Brachiocephalic veins
- pleura, phrenic nerves, trachea
What is the blood supply and venous drainage of the thymus?
- internal thoracic and inferior thyroid arteries
- left brachiocephalic vein
What are structures on the right of the mediastinum associated to?
veins and the right atrium of the heart
Which nerve runs with the trachea in the R Superior mediastinum?
R vagus nerve
What structure does the Right phrenic nerve run with in the Right superior mediastinum?
SVC
Which nerve runs with the aortic arch?
left vagus nerve
Which structure is the left phrenic nerve associated in the left superior mediastinum?
left ventricle of heart
What are the 3 planes of the superior mediastinum from most anterior to posterior?
- venous
- arterial
- trachea and oesophagus
What does the SVC divide into superiorly?
Left and right brachiocephalic veins
what are the branches of the L+R BCVs and which is medial?
- L+R internal Jugular vein, medially,
- L+R subclavian veins, laterally
What is the anatomical position of the bifurcation of the SVC to the L+R BCVs?
posterior to the 1st right costal cartilage
Where, anatomically, does the arch of the Azygous vein join the SVC?
posterior to the 2nd right costal cartilage
Where anatomically does the SVC enter the right atrium?
posterior to the 3rd right costal cartilage
Where does the azygous vein drain?
posterior chest wall
Where does the subclavian vein drain?
the upper limb
what are the internal jugular veins responsible for draining?
head and neck
Which veins drain into the Left BCV?
- veins from anterior chest wall
- internal thoracic arteries
Which surgical procedure are thyroid veins at risk and why?
- drain into the LBCV, mainly in children they protrude above manubrium
- hence are at risk during tracheotomy
How are the vagus nerves related to the BCVs?
R+L vagus nerves are medial to the R+L BCVs
How are the R+L phrenic nerves related to the BCVs?
lateral to the R+L BCVs
What are the 3 branches of the aortic arch from right to left?
- brachiocephalic trunk (BCT)
- left common carotid artery
- left subclavian artery
what level is the arch situated at?
T4/5
Where anatomically does the BCT divide and what structures does it give?
- posterior to right sternoclavicular joint
- R subclavian and R common carotid
where is left subclavian vein anatomically situated?
posterior and L of the trachea
Which vessels do the R and L vagus nerves relate to?
- R vagus nerve is anterior to the R subclavian artery
- L vagus nerve is lateral to the L common carotid artery
Which 2 nerves relate to the arch of the aorta and how?
L vagus nerve and L phrenic nerve lateral to the arch
What level does the Trachea start from and extend to?
- starts at C6
- Carina (bifurcation to L+R main bronchi) at T4/5
Which muscle alters tracheal diameter? Where is it located?
- trachealis posterior
- posterior between the ends of the C shaped cartilage rings
How is it associated with the oesophagus? which nerves associated with the trachea and the oesophagus?
trachea is anterior to the oesophagus and the left recurrent laryngeal nerve in-between
How does the right main bronchus differ from the left?
- wider
- shorter
- more vertical than the left
What alters tracheal diameter at rest?
smooth muscle contraction
What is the function of the oesophagus?
transport of food and fluid through the thorax and diaphragm into the stomach
What is the anatomical position of the oesophagus?
- starts at C6
- passes immediately posterior to trachea and anterior to vertebral column
- aortic arch is anterior on the left
What is the function of the thoracic duct? What is it a continuation of?
- lymphatic efferents from the rest of the body empty into the thoracic duct
- cisterna chyli
Which structures does it lie between? What level does it cross to the left side of the body?
- thoracic (descending) aorta and azygous vein
- T4/5
Which vein does the thoracic duct drain into?
the left brachiocephalic vein at the junction of the L IJV and LScV
Which nodes do the nodes of the lung and the lung hilum drain into? Where are these nodes located
- mediastinal nodes
- clustered around trachea and oesophagus
Which nodes lie superior and inferior to the tracheal bifurcation?
superior and inferior tracheobronchial nodes
Which vessels do the anterior nodes lie around?
around the brachiocephalic veins
Which of 2 structures do all nodes drain into?
- thoracic duct on the right
- communicate with deep cervical nodes
how are lymph nodes clinically relevant?
may be involved in the spread of tumour
What structure in the superior mediastinum can lung tumours affect?
the larynx causing a hoarse voice
Which nodes can become palpable with a lung tumour?
lymph nodes in neck
