Superior Mediastinum Flashcards
What is the parallel of the RML in the left lung?
Lingula
- Not true lobe but region of L lung
How to ID abnormalities of the RML on XR?
- Right heart border will be obscured on frontal view
- Heart will be obscured on lateral view but posterior is clear
How to ID abnormalities of the RUL on XR?
- Opacity will be above the major (horizontal) fissure on frontal view
- Same on lateral view
How to ID abnormalities of the RLL on XR?
- Opacity in lower region w/ blunting of costophrenic angle on frontal view
- Opacity will be in retrocardiac region on lateral view
*Check heart border to see if also possible RML
How to ID abnormalities of LUL on XR?
- Left upper lung opacity on frontal view
- Clear heart borders & retrocardiac region on lateral
*Lingular would cause loss of left ventricle border on both views
How to ID lingular abnormalities?
- Lose left heart border on frontal view
- Heart is hyperdense on lateral view while retrocardiac area is clear
Transverse thoracic plane
- Divides superior & inferior mediastinum
- Aka sternal angle
What divides the mediastinum into superior & inferior parts?
Transverse thoracic plane or sternal angle
What level is the transverse thoracic plane/sternal angle at?
T4-T5
What is most superficial in the superior mediastinum?
Remnant of thymus
What does the superior mediastinum containt?
- Great vessels (arch of aorta, brachiocephalic trunk, left common carotid artery, left subclavian artery, SVC, R&L brachiocephalic veins, bifurcation of pulmonary trunk & roots of pulmonary arteries)
- Trachea
- Esophagus
- Remnant of thymus
- Phrenic, vagus, & LEFT recurrent laryngeal nerves
- Cardiac plexus
- Thoracic duct
Which thoracic level does the SVC form?
1st costal cartilage
Which level does the arch of the aorta form?
Sternal angle (T4-T5)
Ligamentum arteriosum
- Attaches inferior part of aortic arch to superior part of left pulmonary artery
- Remnant of ductus arteriosus
What ligament attaches the aortic arch to the left pulmonary artery?
Ligamentum arteriosum
Name the arteries in the superior mediastinum.
(Right to left)
- Brachiocephalic trunk –> right subclavian artery + right common carotid artery
- Left common carotid artery
- Left subclavian artery
Where do the internal thoracic arteries branch from?
R&L subclavian arteries
What first branches off of the subclavian arteries?
Internal thoracic arteries
What are the internal thoracic arteries also known as?
Mammarian arteries
Name the nerves in the superior mediastinum.
- R&L phrenic nerves (superficial)
- R&L vagus nerves (deep)
- Left recurrent laryngeal nerve
What nerve wraps around the aortic arch (behind the ligamentum arteriosum)?
Left recurrent laryngeal nerve
What nerve wraps around the right subclavian artery?
Right recurrent laryngeal nerve
What does the left recurrent laryngeal nerve wrap around?
Aortic arch
What does the right recurrent laryngeal nerve wrap around?
Right subclavian artery
What symptoms would present if the left recurrent laryngeal nerve is injured?
Voice hoarseness
Damage to what nerve would present as voice hoarseness?
L recurrent laryngeal nerve
What does the left vagus nerve become in relation to the esophagus?
Anterior vagal trunk
What does the right vagus nerve become in relation to the esophagus?
Posterior vagal trunk
Besides from direct nerve damage, what also could cause voice hoarseness?
- Mass in the AP window such as tumor/lymph node enlargement due to compression of L recurrent laryngeal nerve
- Mass in the apex of the R lung due to compression of R recurrent laryngeal nerve
What is the location of the phrenic & vagus nerves in relation to the hilum?
- Phrenic anterior
- Vagus posterior
Where does the thoracic duct empty into?
- Venous system near the union of the L internal jugular & left subclavian veins
- Aka L venous angle
- Where L brachiocephalic vein forms
Describe relative location of the thoracic duct.
Mostly travels up the R side of the body, but crosses midline to left side of the body around T4 level
What pushes the mediastinum away from midline?
- Pleural effusion
- Tension pneumothorax
What pulls the mediastinum away from midline?
- Pulmonary collapse (atelectasis)
- Pneumonectomy
How does a tension pneumothorax differ from a plain pneumothorax?
It has mass effect.
What is the cardiac plexus?
- Autonomic nerve fibers supplying the heart
- Lies anterior to bifurcation of the trachea & posterior to ascending aorta
- Post-ganglionic sympathetic, preganglionic parasympathetic, visceral afferent fibers that extend from plexus along the coronary vessels to components of the conducting system, especially the SA node
- Sympathetic stimulation –> inc rate/force of contractions & dilate coronary arteries
- Parasympathetic stimulation –> slow heart rate, reduce force of contraction, constrict coronary arteries
Origin of phrenic nerves
C3-C5 (anterior rami)
“C3, 4, 5, keep the diagphragm alive!”
What do the phrenic nerves innervate?
Diaphragm
Where does the vagus nerve originate?
Medulla of brainstem
Where do the intercostal nerves originate?
T1-T11 (anterior rami)
Where do the subcostal nerves originate?
T12 (anterior rami)
Location of right vagus nerve in relation to blood vessels.
- Anterior to right subclavian artery
- Posterior to R brachiocephalic vein
Location of left vagus nerve in relation to blood vessels.
- In between left common carotid & left subclavian arteries
- Posterior to L brachiocephalic vein
Location of phrenic nerves in relation to blood vessels.
- Between subclavian arteries & brachiocephalic veins
What is the trachea made up of?
- C-shaped cartilaginous rings
- Posterior aspect is muscular
What are the three most common areas of coronary artery occlusion?
1) LAD of LCA (40-50%)
2) RCA (30-40%)
3) Circumflex branch of LCA (15-20%)
