Posterior mediastinum Flashcards
what are the boundaries of the inferior mediastinum?
- inferior to the plane of T4/5 and the sternal angle
- superior to the thoracic outlet
What are the3 parts of the inferior mediastinum?
- part of the anterior
- middle
- posterior
What are the boundaries of the posterior mediastinum?
- posterior to the pericardial sac and the diaphragm
- from the IV disc between T4 and T5 to the posterior attachment of the diaphragm at T12
List the contents of the posterior mediastinum
- descending (thoracic) aorta
- thoracic duct and mediastinal lymph nodes
- azygous vein= hemi azygous vein
- oesophagus
Which level does the descending aorta extend from and what is its anatomical landmark? where does it extend to?
- T4/5
- 2nd left costal cartilage
- to aortic hiatus in the diaphragm at T12 behind the median arcurate ligament
What are the branches of the descending aorta?
- oesophageal arteries
- posterior intercostal arteries
- subcostal arteries
- bronchial arteries
Where do the oesophageal arteries supply?
middle third of the oesophagus
how many posterior intercostal arteries are there? Where do they supply?
- 9
- supply 9 intercostal spaces from 3-11
Where are the subcostal arteries located? What do they supply?
- inferior to the 12th rib
- supply the posterior abdominal wall
how many bronchial arteries are on the left and how many on the right?
- 2 on the left
- 1 on the right
What vein drains the middle of the oesophagus?
azygous vein
Which arteries branch from the subclavian arteries?
internal thoracic arteries (mammary arteries)
What do the internal thoracic arteries branch to give? What do these vessels anastomose with?
- anterior intercostal arteries
- posterior intercostal arteries branching from the aorta
What is the benefit of the anastomoses between the anterior and posterior intercostal arteries?
in coarctation of the aorta a collateral circulation maybe established
What level does the oesophagus pierce the diaphragm? What is its orientation when it pierces the diaphragm?
- T10
- it swings anteriorly and to the left
What are the 3 levels of the oesophagus?What is the composition of the muscle at the 3 levels of the oesophagus?
- upper 1/3, middle and lower 1/3
- upper=striated voluntary muscle
- middle=mix
- lower=smooth involuntary muscle
What structure is located between the pharynx and the oesophagus?
cricopharyngeal sphincter
What is the function of the cricopharyngeal sphincter?
prevents air being sucked into the stomach during inhalation
how is physiological cardiac sphincter of the stomach formed?
lower oesophagus passes through the Right crus of diaphragm just left of midline and entry is oblique to the stomach
What is the function of the cardiac sphincter?
prevents gastric reflux
What is the nerve supply to the upper oesophagus?
branches of the vagus nerves= recurrent laryngeal nerves
what is the arterial supply and venous drainage of the upper oesophagus?
- internal thyroid arteries
- brachiocephalic veins
which lymph nodes does the upper oesophagus drain to?
deep cervical nodes
What 2 arteries supply the middle oesophagus?
- directly from the the thoracic aorta
- bronchial arteries
What is the nerve supply to the middle of the oesophagus?
oesophageal plexus
which lymph nodes does the middle oesophagus drain to?
tracheobronchial nodes
What is the arterial supply and venous drainage to the lower oesophagus?
- left gastric artery
- venous drainage to the left gastric then hepatic portal vein
What is the nerve supply to the lower oesophagus?
branches from the oesophageal plexus:
- vagus
- sympathetic
wat is the lymph drainage of the lower oesophagus?
- left gastric nodes
- coeliac nodes
Which veins form the porto-systemic anastomoses of the oesophagus?
submucosal veins between the middle and abdominal portions
What effect does cirrhotic liver disease have on the submucosal veins?
raises the portal venous pressure, blood escapes via submucosal veins and in to the azygous vein
once they become dilated and torturous
What are dilated and torturous submucosal veins called? what do the have the potential to do?
- oesophageal varices
- may cause fatal haemorrhage
What are the 4 oesophageal constrictors?
- upper oesophageal sphincter
- aortic arch
- left main bronchus
- diaphragm
how is the pulmonary trunk related to the oesophagus?
crosses anteriorly to it
which heart chamber is related to the oesophagus?
left atrium
Which parts of the body does the thoracic duct not drain lymph from?
- right thorax
- right upper limb
- head and neck
Why do you have to be carful when carrying out thoracic surgery with regards to the lymphatic system?
- care has to be taken to avoid damage to the thoracic duct
- leakage of lymph will cause a chylothorax
what level does the thoracic duct pierce the diaphragm? accompanying which structures?
- T12
- thoracic aorta and azygous vein
Which lymph nodes lie alongside the trachea?
paratracheal nodes
Where are posterior mediastinal lymph nodes located?
behind the heart, adjacent to the oesophagus
Describe lymph drainage in the thorax starting from the lungs.
- pulmonary nodes drain into bronchopulmonary (around main bronchi)
- bronchopulmonary drain into inf. and sup. Tracheobronchial nodes
- Tracheobronchial and Posterior mediastinal nodes drain into paratracheal lymph nodes
- paratracheal, parasternal and anterior mediastinal all drain into Bronchomediastinal lymph trunks
Which veins branch from the Azygous vein?
intercostal veins
Where does the azygous vein begin from?
lumbar and subcostal veins
Which structure does the azygous vein lie on?
the vertebral column
what is the route taken by the azygous vein as it enters the SVC? what landmark indicates the entry of the azygous vein into the SVC
- passes posterior to R lung hilum then superior to it as it arches into SVC at
- 2nd R Costal Cartilage
What are the 2 parts of the Hemi-azygous vein?
- lower
- accessory (upper)
Which veins does the lower Hemi azygous vein have connections with?
left renal veins
what level does the lower H. Azy vein cross to the right?
T9
Where does the accessory hemi azygous vein decrease from? What level does it cross to the right?
- decreases from the 4th intercostal space on the left
- crosses to right at T8
