Mediastinum and Imaging of the Thorax Flashcards
Define mediastinum. Describe the four borders of the medianstinum.
“Region in the thorax BETWEEN the two pleura cavities” (the lungs). NOTHING ABOVE. NOTHING BELOW.
Superior Border: BOTTOM of T4
Anterior Border: Everything in front of the fibrous pericardium
Posterior Border: Everything behind the fibrous pericardium.
Middle Medianstinum: area of fibrous pericardium
You remove the chest wall and look directly into the cavity Describe what you see in the anterior MIDDLE medianstinum (level 1). What is in the superior medianstinum (level 1)
You would see the 2 lungs, the fibrous pericardiium, and the inferior part ONLY of the thymus. Note that the Thymus is in both the Superior and Middle (middle) medianstinum
What is the most anterior bone of the medianstinum? What is the most posterior wall?
Anterior wall of the manubrim of the sternum. The most posterior wall is the upper thoracic vertebral column.
What lies in the second level of the superior medianstinum? Describe specifics. What is in the middle second level of the medianstinum?
The venous plane is in the second level of the superior medianstinum. This specifically includes the right and left brachiocephalic veins, as well as the SUPERIOR vena cava. Middle second level contains the CONTENTS of the pericardium (the actual heart)
What lies in the third level of the superior medianstinum?
The arterial plane lies in the second level. They specifically include the aortic arch, the ascending aorta, the descending aorta, and the left common carotid and left subclavian arteries. In addition, you will find the brachiocephalic trunk. So you ultimately find SIX (6) arteries. I know, the aortic arch is SUPPOSED to be counted 3 times. Besides these, the left vagus nerve, the left recurrent laryngeal nerve, and the ligamentum arteriorsum all lie here.
Name a complication of an aortic anyeurism.
Stretching or compressing of the vagus nerve..,note that the vagus nerve litereally lies directly on it.
What is the left recurrent larengeal nerve?
It is a branhc off of the vagus nerve. It Is on both the rigth and th eleft, but the right branches off in the neck, so diseases manifest differently. The recurrent left larangeal U turns and goes back to the arch of the aorta. It is ALWAYS immeditaely to th eleft os the ligamentum arteriosa.
What is the ligamentum arteriosum? What is this a landmark for?
It is what remains of the ductus arteriosus. Left to the ligamentum arteriosa is the vagus nerve.
What lies in the fourth layer of the superior mediansteinum?
The trachea. Note that it specifically bifurcates at T4
What lies in the 5th layer, full fledged posterior of the medianstinum?
- The esophagus, which lies directly on the vertebral column. It is immediately behind the pericardium. more specifically, it is immediately behind the left atrium, so if th eleft atrium enlargens, it will push back against the vertebral column, blocking the esphagus and leading to disphasia (indication of left atrial enlargement).
2, The thoaracic aorta. Note that it is covered with branches of th evagus nerve. and that both vagus nerves travel up the thoracic aorta. The vagus nerves are on the FRONT and BACK of the aorta (not the left or right of it.). AS a result, left vagus = anterior trunk and right vagus = posterior trunk of the aorta. - Thoracic duct: Inaccurately drawn by Netter. It is SUPPOSED to lie directly behind the esphagus, between the azygous vein and the aorta and btween the esophagus and vertrebral column. Essentially, it is in the dead center.
4, Azygos vein. Note that it technically does not have a pair on the left side of the meidanstiunum, but it does (has a different name.). It works as venous drainage for much of the thoracic wall. Right intercostal veins drain into it,. Aygos vein ultimately drains into SUPERIOR vena cava.
From a right view of the mediansteinum, what is visible?
Esophagus, trachea, and SVC + IVC, and the RIGHT atrium. Note that the SVC and IVC pass vertically in a straight line. Used for catheters. In addition to all of this, you can see the sympathetic chain, the azygos vein (which arches over the pericardium to get into the superior vena cava), the splanchnic nerve, the vagus nerve (looks like it lies on trachea), and the phrenic nerve (which lies on the vena cava. Literally passes in front of the hilus of the lungs in the plane o fthe medialstinual pleura and the pericardium. It is heading to diaphragm, but in order to get to thorax it has to stay between the plane between the medianstinum and the pericardium. Contains both sensory and motor innervation.)
+ intervostal nerves (ventral rami)
What can be seen from the left tmedianstinum?
- Ligamentum arteriosum
- Phrenic nerve
- Vagus nerve, which heads more posteriorly than the phrenic nerve, literally passing BEHIND the hialis of the lung. Just look for the azygos vein. It passes behind the azygos vein and heads towards esophagus.
- Intercostal nerves (ventral rami)
- Recurrent larengeal nerve
6, Aorta, which arches over hialus of the left lung - Hemiazygos vein (corresponds to azygos vein on the right side.). It is shorter and passes behind aorta and vertebral column. Also drains into superior vena cava. REveiw slides 14 to 23 for images you need to know.
When looking at CT/cross sectional images, how would you know which part of the lung is superior or inferior or middle?
Superior lobe is most anterior to the body. Inferior lobe is in the posterior of body. Middle load can be herd form th eright side of the body (for the right lung. Left lung does not have middle component.)
Where is the last place you will see the trachea before it gets to the superior part of the body? What lies directly below T4?
T4. Anything above T4 and you WILL NOT see the trachea. You know you are lower than T4 if you see a heart in the CT.
What are the levels of the superior medialstinum?
- Above aortic arch
- At aortic arch
- Below aortic arch
- T4
