Dissection of the Superior Mediastinum Flashcards
Position of right pulmonary artery?
Posterior to SVC and aorta
Position of left pulmonary artery?
Anterior to descending aorta
Boundaries of superior mediastinum?
- Superiorly: thoracic aperture
- Inferiorly: sternal angle
- Laterally: mediastinal surfaces of parietal pleura
12 major structures found in the superior mediastinum?
- Thymus
- Right and left brachiocephalic veins
- Left superior intercostal vein
- SVC
- Aortic arch and its 3 branches
- Trachea
- Esophagus
- Phrenic nerves
- Vagus nerves
- Left recurrent laryngeal nerve
- Thoracic duct
- Other small nerves, vessels, and lymphatics
From what nerves do the recurrent laryngeal nerves branch?
Vagus nerves
Most anterior component of the superior mediastinum?
Thymus
What is located immediately posterior to the thymus?
Left and right brachiocephalic veins
At what junction do the right and left brachiocephalic veins form?
Junction of subclavian and jugular veins
Which brachiocephalic vein crosses the midline? At what level does it do this?
How is this different in children?
Left one posterior to manubrium
In children in passes the midline superior to manubrium so is less protected
Position of beginning of right and left brachiocephalic veins?
Posterior to medial end of right/left clavicles
Venous tributaries of right brachiocephalic vein?
- Vertebral vein
- 1st posterior intercostal vein
- Internal thoracic veins
- Inferior thyroid + thymic veins
Surface projection of transition from L and R brachiocephalic veins to SVC?
Lower edge of right 1st costal cartilage close to right sternal border
Venous tributaries of left brachiocephalic vein?
- Vertebral vein
- 1st posterior intercostal vein
- Left superior intercostal vein
- Inferior thyroid + thymic veins
- Pericardial veins
How do L and R brachiocephalic veins differ?
Right one is shorter and more vertical
Surface projections of SVC?
- Begins at lower edge of right 1st costal cartilage close to right sternal border
- Enters RA at lower edge of 3rd costal cartilage close to right sternal border
Veins draining into SVC other than brachiocephalic veins?
- Azygos vein
2. Optional pericardial and mediastinal veins
Describe the venous access for central and dialysis lines.
Lines introduced through venous punctures in axillary, subclavian, or internal jugular veins and passed through the main veins of the superior mediastinum to reside in the distal portion of the SVC or RA
What kind of procedures use the vertical axis between the SVC and IVC to access the IVC?
- Transjugular liver biopsy
- Transjugular intrahepatic portosystemic shunts
- Insertion of IVC filter to catch emboli dislodged from veins in the lower limbs and pelvis (in patients with deep vein thrombosis)
Describe the vertebral levels/surface projection of the aortic arch.
- Starts at T4/T5
- Reaches T3/T4 (mid-manubrium)
- Ends at T4
Position of SVC in regards to ascending aorta?
Right
Position of infundibulum of RV in regards to ascending aorta?
Anterior
Position of pulmonary trunk in regards to ascending aorta?
Anterior
Position of right main bronchus in regards to ascending aorta?
Posterior
Position of right auricle in regards to ascending aorta?
Right/Anterior
Position of right pulmonary artery in regards to ascending aorta?
Posterior
Position of LA in regards to ascending aorta?
Posterior
3 portions of thoracic aorta?
- Ascending aorta
- Aortic arch
- Descending aorta
Other name for descending aorta?
Thoracic aorta
What crosses all 3 branches of the aortic arch anteriorly?
Left brachiocephalic vein
Veins draining into the left superior intercostal vein?
- 2nd posterior intercostal vein
- 3rd posterior intercostal vein
- 4th posterior intercostal vein (sometimes)
- Left bronchial veins
- Left pericardiacophrenic vein (sometimes)
What does the left superior intercostal vein drain into?
Left brachiocephalic vein
What vein does the left superior intercostal vein connect with inferiorly? 2 names
Accessory hemiazygos vein = superior hemiazygos vein
Pathway of the left superior intercostal vein?
Over left side of aortic arch => lateral to left vagus nerve => medial to left phrenic nerve => enters left brachiocephalic vein
First branch of the aortic arch?
Brachiocephalic trunk
Surface projection of brachiocephalic trunk?
Posterior to manubrium
Direction of ascension of brachiocephalic trunk?
Posteriorly and to the right
At what level does the brachiocephalic trunk divide? Into what? What does each supply?
Upper edge of right sternoclavicular joint into:
- Right common carotid artery: right side of head and neck
- Right subclavian artery: right upper limb