TBL 13: Superior Mediastinum Flashcards
Where is the border between the superior mediastinum and the inferior mediastinum?
There is an imaginary transverse plan between the sternal angel and disc T4/T5 that separates the superior mediastinum from the inferior mediastinum.
What is the most superficial structure in the superior mediastinum and what happens to this structure after puberty?
The thymus (a primary lymphatic organ) is the most superficial structure in the superior mediastinum.
After puberty, the thymus progressively involutes and is largely replaced by white fat.
Which vessels converge to make the SVC?
The right and left brachiocephalic veins converge to make the SVC, so the SVC receives all venous blood superior to the diaphragm except from the coronary circulation.
Where is the ascending aorta located and what are its only branches?
The ascending aorta is intrapericardial and the left and right coronary arteries are its only branches.
What is SVC syndrome caused by and what are its characteristics?
SVC syndrome is caused by compression of the SVC by growing tumors in the superior lobe of the right lung.
It is characterized by shortness of breath, distension of veins in the neck, and eventual edema of the face.
Where does the trachea bifurcate into the main bronchi? What two main structures travel this region and where in relation to the bronchi to they each travel?
The trachea bifurcates into the main bronchi at the transverse plan separating the superior and inferior mediastina.
The esophagus is travels posteriorly to the trachea and both main bronchi.
The arch of the aorta passes posteriorly over the left main bronchus.
Why can dyspnea or dysphagia occur when an aneurysm forms in the ascending aorta?
An aneurysm in the ascending aorta may compress the trachea, esophagus, and recurrent laryngeal nerve, causing difficulty in breathing and swallowing.
Where does the right recurrent laryngeal nerve travel?
Where does the left recurrent laryngeal nerve travel and where does this nerve arise from?
The right recurrent laryngeal nerve loops under the right subclavian artery.
The left recurrent laryngeal nerve loops under the arch of the aorta and arises from the left vagus nerve immediately lateral to the ligamentum arteriosum.
Why can paralysis of the left vocal cord and resulting hoarseness be associated with left apical lung tumors or an aneurysm of the aortic arch?
A left apical lung tumor or an aneurysm of the aortic arch may compress the recurrent laryngeal nerve which supplies all but one of the laryngeal muscles.
Which plexuses does the vagus nerve contribute to?
After giving off the recurrent laryngeal nerves, the vagus nerve contibutes to the cardiac, pulmonary and esophageal plexuses.
Where do the phrenic nerves travel?
The phrenic nerve descends through the superior mediastinum lateral to the vagus nerve and posterior to the brachiocephalic veins. It then courses along the lateral aspects of the pericardial sac to reach the diaphragm.
