Mediastinum and Imaging of the Thorax Flashcards
what are the regions of the mediastinum?
mediastinum = region between the pleural spaces
superior - above manubriosternal junction
anterior - in front of pericardium
middle - within pericardium
posterior - behind pericardium
what are the 5 layers of the superior mediastinum?
from anterior to posterior:
1. thymus
2. venous plane: SVC, branching into R/L brachiocephalic V
3. arterial plane: part of ascending aorta, all of aortic arch, brachiocephalic trunk, L common carotid, L subclavian artery, part of descending aorta, L. vagus, L recurrent laryngeal nerve, ligamentum arteriosum
4. tracheal plane
5. esophageal plan
What are the 3 major veins found in the superior mediastinum (think about it anatomically)?
superior vena cava, branching into R/L brachiocephalic vein
*note R brachiocephalic is more vertical than left because SVC is shifted to the right
*venous plane is 2nd most anterior after thymus
what arteries are found in the arterial plane of the superior mediastinum?
- part of ascending aorta (excluding part that is within pericardium and therefore in middle mediastinum)
- aortic arch
- brachiocephalic trunk, L common carotid, L subclavian (branches off aortic arch)
- part of descending aorta (continues on into posterior mediastinum behind pericardium)
what nerves are found in the arterial plane of the superior mediastinum?
- left vagus nerve: crosses over surface of aortic arch
- left recurrent laryngeal nerve: branch of vagus, hooks under aortic arch (immediately left of ligamentum arteriosum) then goes back up to neck to innervate larynx
in which region of the mediastinum are the following structures found together?
- esophagus
- thoracic duct
- azygos vein
- thoracic aorta
- esophageal plexus
- anterior vagal trunk
posterior mediastinum:
- esophagus: most anterior part, immediately behind pericardium (against back wall of L atrium)
- thoracic duct: right behind esophagus, lymphatic drainage
- azygos vein: unpaired vein, R intercostal veins drains into here, which drains into SVC
- thoracic aorta: continuation of descending aorta, now behind esophagus and in midline
- esophageal plexus: nerves on surface of esophagus, formed from branches of L vagus (CN X)
- anterior vagal trunk: after esophagus, vagus reforms into single nerve
describe how the thoracic aorta and esophagus change positions as they descend inferiorly
thoracic aorta and esophagus are found together in posterior mediastinum (recall though that esophagus is also most posterior plane of superior mediastinum)
esophagus starts in midline but moves to left to reach opening in diaphragm, while thoracic aorta has to move left
to fit, the thoracic artery moves behind (posterior to) the esophagus
when viewing the mediastinum from the right (with lung removed):
a. ____ arches over R main bronchus to drain into SVC
b. ____ is behind the hilus, crossing between the trachea and arch of the azygous vein
c. ____ is in front of the hilus, between the parietal pleura and pericardium
d. _____ arises from the sympathetic chain and enters the abdomen
when viewing the mediastinum from the right (with lung removed):
a. AZYGOS V arches over R main bronchus to drain into SVC
b. VAGUS N is behind the hilus, crossing between the trachea and arch of the azygous vein
c. PHRENIC N is in front of the hilus, between the parietal pleura and pericardium (allows it to innervate both)
d. GREATER SPLANCHNIC N arises from the sympathetic chain and enters the abdomen
when viewing the mediastinum from the left (with the lung removed):
a. ______ connects the aorta to the pulmonary artery (embryonic remnant), with the _____ nerve right next to it
b. ______ nerve is behind the hilus
c. ______ nerve is in front of the hilus, between the parietal pleural and pericardium
d. ______ passes over the root of the L lung
e. L intercostal veins drain into the _______
when viewing the mediastinum from the left (with the lung removed):
a. LIGAMENTUM ARTERIOSUM connects the aorta to the pulmonary artery (embryonic remnant), with the RECURRENT LARYNGEAL nerve right next to it
b. VAGUS nerve is behind the hilus
c. PHRENIC nerve is in front of the hilus, between the parietal pleural and pericardium
d. AORTA passes over the root of the L lung
e. L intercostal veins drain into the HEMIAZYGOS VEIN - shorter than azygos vein on R, has multiple communications to R side to drain into SVC
considering anatomical structure, why does it make sense that left atrium enlargement can cause difficulty swallowing?
esophagus is just posterior to L atrium
enlargement of L atrium would cause compression of esophagus
what structure is found between the azygos vein and the aorta?
thoracic duct (lymphatic drainage)
where are the thoracic aorta and azygos vein in relation to the esophagus?
thoracic aorta: posterior/L of esophagus
azygos vein: posterior/R of esophagus
what structure travels over the R and L root of the lung, respectively?
arch of azygos vein: over R root
arch of aorta: over L root
