Posterior mediastinum Flashcards
What are the relations of the descending thoracic aorta?
- The descending thoracic aorta begins at T4/5 level (end of aortic arch).
- It initially descends to the left of the vertebral column, but then crosses to become anterior.
- The oesophagus and left main bronchus are anterior to it.
- It passes posterior to the diaphragm to enter the abdominal cavity.
What are the branches of the descending aorta?
- Bronchial arteries
- Oesophageal arteries
- Posterior intercostal arteries
- Subcostal arteries
- Superior phrenic arteries
What is the structure of the oesophagus?
- The oesophagus begins just inferior to the cricoid cartilage at level of C6 vertebrae.
- It passes inferiorly in the midline and then crosses to the left, before passing through the diaphragm at level of T10 vertebrae (oesophageal hiatus).
- The oesophagus is 27cm long.
- Upper 1/3 of muscularis propria consists of striated muscle.
- Middle 1/3 consists of striated and smooth muscle.
- Lower 1/3 consists of smooth muscle.
What are the anterior relations of the oesophagus?
- Trachea
- Left atrium
- Left main bronchus
- Recurrent laryngeal nerves
What are the posterior relations of the oesophagus?
- Vertebral column
- Thoracic duct
- Azygos/hemiazygos veins
- Descending aorta
What are the relations of the oesophagus to the left?
- Thoracic duct
- Aorta
- Left subclavian artery
- Left lung
What are the relations of the oesophagus to the right?
- Lung
- Azygos vein
What is the blood supply to the oesophagus?
Arteries: - Upper 1/3: Inferior thyroid artery - Middle 1/3: Oesophageal branches from descending aorta - Inferior 1/3: Left gastric artery Veins: - Upper 1/3: Inferior thyroid vein - Middle 1/3: Azygos vein - Lower 1/3: Left gastric vein
What is the innervation of the oesophagus?
- Upper: Recurrent laryngeal nerves, sympathetics from the middle cervical ganglion.
- Lower: Fibres from the oesophageal plexus.
What is the lymphatic drainage of the oesophagus?
- Upper 1/3: Deep cervical nodes
- Middle 1/3: Mediastinal nodes
- Lower 1/3: Gastric nodes
What is the structure of the azygos venous system?
- The azygos/hemiazygos veins form at the level of L1/2 vertebrae from the union of the upper 2 lumbar veins and the subcostal veins.
- The arch of azygos winds around the right main bronchus to drain into the SVC at T4 level.
- The hemiazygos/accessory hemiazygos veins drain cross the midline at levels T8/9 to drain into the azygos vein.
- The posterior intercostal veins drain into the azygos system.
- The supreme intercostal veins (supplying 1st intercostal space) drain into the brachiocephalic veins.
What asymmetry is there between the right and left azygos systems?
- Right superior intercostal veins (draining 2nd and 3rd intercostal spaces) drain into azygos vein.
- Left superior intercostal veins drain into the left brachiocephalic vein.
What are the relations of the thoracic duct?
- The thoracic duct begins as a continuation of the cisterna chyli in the abdomen.
- It crosses the diaphragm to the right of the descending aorta through the aortic hiatus.
- It ascends through the thoracic cavity between the aorta (left) and azygos vein (right).
- It crosses the the midline from right to left at T4/5.
- It arches forward to drain into the junction of the left subclavian and internal jugular vein behind the left sternoclavicular joint.
What is the drainage of the thoracic duct?
- Both lower limbs
- Abdomen
- Left half of thorax
- Left upper limb
- Left side of head and neck
What are the tributaries of the thoracic duct?
Inferior - superior:
- Descending thoracic trunks
- Bronchomediastinal trunks
- Subclavian trunks
- Jugular trunks
