Posterior Mediatsinum

Question 1

Thoracic (descending) aorta

Answer 1

Continuation of the arch of aorta, begins at lower edge of T4 vertebra. Descends through posterior mediastinum to the left of the vertebra, becomes more medically located as it moves. At inferior border of T12, thoracic aorta becomes abdominal aorta, passes through aortic hiatus of the diaphragm

Question 2

Branches of thoracic aorta

Answer 2

Arise in 3 vascular planes; unpaired branches to viscera extend anteriorly, paired branches to viscera extend laterally, paired segmental parietal branches extend posterolaterally

Question 3

Posterior intercostal arteries

Answer 3

Paired parietal branches. Nine pairs branch from posterior aspect of aorta, supplying intercostal spaces (except the first two). Pass posteriorly and laterally in parallel with the ribs

Question 4

Bronchial arteries

Answer 4

Paired visceral branches, usually one or two. Left bronchial arteries arise directly from thoracic aorta, right bronchial arteries branch from right posterior intercostal artery. They supply the tracheobronchial tree.

Question 5

Oesophageal arteries

Answer 5

Unpaired visceral branches, arise from anterior aspect of aorta. In most individuals there are two, there can be five. Supply the oesophagus.

Question 6

Superior phrenic arteries

Answer 6

Arise from anterior aspect of thoracic aorta at aortic hiatus varying in number. Supply superior aspect of diaphragm

Question 7

Oesophagus

Answer 7

Muscular tube connecting pharynx to stomach (allows food to enter digestive system)
Passes into posterior mediastinum from superior mediastinum, descending posteriorly to the arch of the aorta and the heart. Initially positioned to the right, oesophagus deviates to the left as it moves downwards. Leaves the mediastinum via oesophageal hiatus of diaphragm

Question 8

Oesophageal plexus

Answer 8

Network of nerves surrounding oesophagus as it descends comprising of branches from left and right vagus nerves. Above the diaphragm, fibres of the plexus converge to form anterior vagus trunk and posterior vagal trunk, which travel along the surface of the oesophagus as it exits the thorax

Question 9

Thoracic duct

Answer 9

Largest lymphatic vessel, allowing return of lumps from most of the body (except right superior quadrant) into the venous system
Duct originates from cisterna chyli in abdomen and enters mediastinum via aortic hiatus
Ascends to lie anterior to T6-T12 vertebra, then deviates left as it ascends into superior mediastinum.

Question 10

Thoracic duct in posterior mediastinum receives lymphatic drainage from

Answer 10

Intercostal spaces and neighbouring structures through branches

Question 11

Azygous vein

Answer 11

Formed by union of right lumbar vein and right subcostal vein. Enters mediastinum via aortic hiatus and drains into superior vena cava

Question 12

Hemiazygos vein

Answer 12

Union of left lumbar vein and left subcostal vein. Enters mediastinum through left crus of diaphragm, ascending on left side. At T8, turns right and combines with Azygous vein

Question 13

Accessory hemiazygos vein

Answer 13

Formed by union of fourth to eighth intercostal veins. Drains into azygos vein at T7

Question 14

Sympathetic trunks

Answer 14

Paired bundles of nerves extending from base of skull to coccyx. Thoracic region - thoracic sympathetic trunks (descend through thorax, lie within posterior mediastinum). Lower thoracic splanchnic nerves continue inferiorly to supply abdomen viscer