Superior & Posterior Mediastinum Flashcards
What is the course of the aorta?
- ascending aorta as it comes out of LV
- gives rise to R & L coronaries
- arch goes upwards, backwards to the left (superior mediastinum)
- begins and ends at manubriosternal – T4/T5
- arches over:
- L pulm artery
- L pulm veins
- L main bronchi
- branching of pulmonary trunk (connected to it via ligamentum arteriosum)
- becomes descending thoracic aorta
- descends midline behind oesophagus and anterior to VC
- enters diaphragm thru aortic hiatus between the crura @T12
What are the major branches of the aorta?
- First brances are R & L coronares off ascending
- Arch supplies head, neck, and upper limb
- Brachiocephalic trunk: –> R subclavian & R carotid
- L carotid
- L subclavian
Descending thoracic aorta gives off:
- posterior intercostal arteries
- bronchial areteries @ hilum of lungs
- oesophageal branches
- minor pericardial branches
What are the contents of the superior mediastinum?
Superficial to deep:
- thymus (if present)
- great veins
- aortic arch + vagus and phrenic nerves
- trachea
- oesophagus
- thoracic duct
- L recurrent laryngeal nerve
What are the contents of the posterior mediastinum?
Superior posterior:
- trachea
- oesophagus
- R & L recurrent laryngeal nerves
- thoracic duct (on back of oesophagus)
Deep posterior:
- descending thoracic aorta
- oesophageus (vagal plexus on front, thoracic duct on back)
- azygous vein
- sympathetic trunks
What is the origin and course of the jugular veins?
- drain the head and neck
- into subclavian vein (drains upper limb)
- into brachiocephalic veins (@medial clavicle)
- which join into SVC (@1st R costal cartilage)
What is the origin and course of the subclavian veins?
- drain the upper limb
- receive drainage from head and neck via IJVs
- drain into brachiocephalic veins (@medial clavicles)
- which form the SVC (@1st R costal cartilage)
What is the origin and course of the brachiocephalic veins?
- drainage from IJV –> subclavians
- subclavians branch @ medial clavicle
- form SVC (@1st R costal cartilage)
- R brachiocephalic is shorter and more vertical
- L brachiocephalic crosses over to left (@1st R costal cartilage)
What is the origin and course of the superior vena cava?
- Brachiocephalic veins join (@1st R costal cartilage)
- drainaige from IJVs > subclavians > brachiocephalics
- SVC enters peridcardium @2nd R costal cartilage
- SVC enters RA @3rd R costal cartilage
- venous return from head, neck, and upper limbs
What is the azygous system of veins?
- ascends the R vertebral column arching over the R lung root
- enters SVC posteriorly @ 2nd R costal cartilage
- venous return from
- posterior intercostal veins
- thoracic walls
- everything in thorax except heart
- draining descending aorta supply:
- bronchial, oesophageal, pericardial veins
What is the course of the trachea?
- extends through superior mediastinum at T4/T5
- splits into R & L main bronchi
What is the course of the oesophagus?
superior mediastinum:
- posterior to trachea
- descends midline
posterior mediastinum:
- passes left into diaphragm thru oesophageal hiatus @ T10
- in front of descending aorta and VC
What is the course of the thoracic duct?
- begins at cisterna chyli
- distal end, drains lymph from intestinal trunk and lumbar trunks
- posterior to abdominal aorta on anterior L1 & L2
- collects all lymph from below the diaphragm (pelvis, abdomen, lower limbs)
- always on the back of the oesophagus, anterior to aorta & VC
- ascends upwards and empties into junction at L IJV and L subclavian vein
What is the course of the R vagus nerve?
- cranial nerve
- runs in carotid sheath (int. carotid and jugular vein)
- runs medially, alongside trachea (phrenic lateral)
- behind lung root (phrenic anterior)
- to anterior oesophagus
- joins w/L vagus to form an oesophageal nerve
- gives off R recurrent laryngeal nerve @ R subclavian artery
- hooks around the artery and ascends the right tracheoesophageal groove to innervate larnyx
What is the course of the L vagus nerve?
- cranial nerve
- runs in carotid sheath (int. carotid and jugular vein)
- lateral to aortic arch (can’t get to trachea)
- behind lung root (phrenic anterior)
- onto anterior oesophagus
- meets R vagus to form an oesophageal nerve
- gives off L recurrent laryngeal nerve at arch of aorta
- hooks around ligamentum arteriosum
- under arch of aorta
- back to laryngeal structures in the L tracheoesophageal groove
What is the course of the phrenic nerve?
- branch of cervical plexus (ventral rami C3, 4, 5)
- descends on scalenus anterior
- passes between subclavian artery and vein
- passes anterior to the lung root (bronchi & pulm vessels)
- pierces and innervates the diaphragm
- R thru caval orifice @ T8
- L into muscle of L dome
- R is lateral to venous structures (SVC, RA, IVC)
- L is lateral to arterial structures (aortic arch, LV)
Innervation:
- motor: abdominal surface of diaphragm
- sensory: mediastinal & diaphragmatic pluera, pericardium