TBL13 - Superior Mediastinum Flashcards
What separates the superior and inferior mediastinum?
An imaginary transverse plane between the sternal angle and disc at T4/T5 separates the superior mediastinum from the inferior mediastinum
What is the most superficial structure in the superior mediastinum? What occurs to this structure after puberty?
1) The thymus, a primary lymphatic organ, is the most superficial structure in the superior mediastinum
2) After puberty, the thymus progressively involutes and is largely replaced by white fat; thus, the thymus is difficult to identify in the cadaver
What marks the origin of the SVC? What does the SVC receive?
1) The origin of the left brachiocephalic vein and its union with the right brachiocephalic vein marks the origin of the SVC
2) Thus, the SVC receives all venous blood superior to the diaphragm except from the coronary circulation
What do growing tumors in the superior lobe of the right lung cause?
Growing tumors in the superior lobe of the right lung cause progressive compression of the SVC that creates the SVC syndrome, characterized by shortness of breath, distension of veins in the neck, and eventual edema of the face
What are two unique characteristics of the ascending aorta?
1) The ascending aorta is intrapericardial
2) The left and right coronary arteries are its only branches
What protects the arch of the aorta and proximal brachiocephalic artery? What are two branches of the brachiocephalic artery? What are another two branches of the aorta?
1) The arch of the aorta and proximal brachiocephalic artery (aka trunk) are protected by the sternal manubrium
2) The two terminal branches of the brachiocephalic artery are the right common carotid artery and right subclavian artery
3) The other two branches of the arch of the aorta are the left common carotid and left subclavian artery
What does the arch of the aorta pass posteriorly? What is the esophagus posterior to? What does the trachea bifurcate into and where?
1) The arch of the aorta passes posteriorly over the left main bronchus
2) The esophagus is posterior to the trachea and both main bronchi
3) The trachea bifurcates into the main bronchi at the transverse plane separating the superior and inferior mediastina
Why can dyspnea or dysphagia occur when an aneurysm forms in the ascending aorta?
The aneurysm may exert pressure on the trachea, esophagus, and recurrent laryngeal nerve, causing difficulty in breathing and swallowing
Where do the left and right recurrent laryngeal nerves travel? Where does the left recurrent laryngeal nerve arise from?
1) The left and right recurrent laryngeal nerves loop under the arch of the aorta and right subclavian artery, respectively
2) The left recurrent laryngeal nerve 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?
1) Because of the intimate relationship of the recurrent laryngeal nerve to the apex of the lung, this nerve may be involved in apical lung cancers
2) This involvement usually results in hoarseness owing to paralysis of a vocal fold (cord) because the recurrent laryngeal nerve supplies all but one of the laryngeal muscles
After giving off the recurrent laryngeal nerves, what do the vagus nerves contribute to?
After giving off the recurrent laryngeal nerves, the vagus nerves contribute to the cardiac, pulmonary, and esophageal plexuses
Where do the phrenic nerves travel?
1) The phrenic nerves descend through the superior mediastinum lateral to the vagus nerves and posterior to the brachiocephalic veins
2) The phrenic nerves course along the lateral aspects of the pericardial sac to reach the diaphragm
