HS2-18 Mediastinum Flashcards
What is the definition of the mediastinum?
central part of chest between pleural cavities
What is the superior border of the mediastinum?
thoracic inlet
What is the inferior border of the mediastinum?
diaphragm
What is the lateral border of the mediastinum?
pleural cavity (on both sides)
What is the anterior border of the mediastinum?
sternum/thoracic wall
What is the posterior border of the mediastinum?
vertebral column
What structure defines the the aortic arch?
the transthoracic plane — intersects ascending and descending aorta
What structure does the transthoracic plane intersect in the thorax?
trachea
What are the boundaries of the transthoracis plane?
runs from sternal angle (anterior) to IV disc between T4/T5 (posterior)
What are the four compartments of the mediastinum?
superior
anterior
middle
posterior
The middle mediastinum is bordered by
the pericardium
Give an example of a mediastinal mass.
thymoma (originating from residual thymus/thymic tissue)
What are the borders of the superior mediastinum?
superior = thoracic inlet
inferior = transthoracic plane
What gland is found in the superior mediastinum?
thymus gland
What veins are found in the superior mediastinum?
superior vena cava
brachiocephalic veins
azygos vein
hemiazygos vein
posterior intercostal veins
What is the fate of the thymus gland?
disintegrates after puberty and gets replaced with fat
The brachiocephalic veins drain
the subclavian and internal jugular veins
How can you differentiate between the left and right brachiocephalic veins?
left is longer and more obliquely oriented than right
Where is the azygos vein found?
right side of vertebral bodies, posterior to right main bronchus
The azygos vein drains into
the superior vena cava
The hemiazygos vein is found where?
left side of vertebral bodies
The hemiazygos vein drains into
the azygos vein
The posterior intercostal veins drain into
the azygos vein (right side)
the hemiazygos vein (left side)
What are the three branches that come off the arch of the aorta?
brachiocephalic artery/trunk
left common carotid artery
left subclavian artery
How does the brachiocephalic artery/trunk further branch after coming off the aortic arch? (2)
branches into right common carotid artery + right subclavian artery
[therefore, brachiocephalic artery itself is in mediastinum, but its branches are not]
What nervous structure(s) is/are found in the superior mediastinum?
vagus nerve (CN X)
How can you differentiate between the right vagus nerve and left vagus nerve?
right vagus nerve = runs between right brachiocephalic vein + brachiocephalic trunk
left vagus nerve = runs underneath left brachiocephalic vein and underneath aortic arch
Differentiate between the right and left recurrent laryngeal nerves in the context of the mediastinum.
right recurrent laryngeal nerve does not reach mediastinum
left recurrent laryngeal nerve loops around arch of aorta to “recur” to larynx
How does the esophagus exit the thorax?
through esophageal hiatus in diaphragm
What is the anterior border of the anterior mediastinum?
sternum/thoracic wall
What is the posterior border of the anterior mediastinum?
pericardium
What is the superior border of the anterior mediastinum?
transthoracic plane
What are the contents of the middle mediastinum? (3)
heart
roots of great vessels
phrenic nerves
What is the superior border of the posterior mediastinum?
transthoracic plane
What is the anterior border of the posterior mediastinum? (2)
pericardium
diaphragm
What is the posterior border of the posterior mediastinum?
bodies of T5-T12
What are the contents of the posterior mediastinum? (6)
vagus nerve
thoracic splanchic nerves
descending aorta
azygos system
thoracic duct
esophagus
[three-and-a-half-geese and a duck]
The esophageal plexus is derived from
the vagus nerve
Differentiate between the anterior and posterior vagal trunk.
anterior vagal trunk = derived from left vagus
posterior vagal trunk = derived from right vagus
The thoracic splanchic nerves branch from
the sympathetic trunks, and run anteriorly to the vertebral bodies
(T/F) Sympathetic trunks are considered to be a part of the mediastinum.
False. By definition, they’re not considered to be in the mediastinum because they are lateral to the vertebral bodies
Draw a diagram of the branches of the descending aorta in the posterior mediastinum.
In which mediastinal compartment are no nerves found?
anterior mediastinum
