1. THORACIC CAVITY
MEDIASTINUM

2. Mediastinum Mediastinum = space between lungs. Superior mediastinum:
Separated from inferior by horizontal plane between sternal angle and IV disc T4-T5.
Fig. 1.34, p 135.

3. Mediastinum
Inferior:
Anterior:
Middle:
Posterior:

4. Superior Mediastinum Retrosternal: Prevertebral:
Great vessels and branches.
Thymus.
Prevertebral:
Trachea
Esophagus
Thoracic duct
Sympathetic trunks
Vagus nerves

5. Inferior Mediastinum Anterior: Middle: Thymus, fat, lymph nodes
Pericardium
Phrenic nerves
Pericardiacophrenic artery
Heart and great vessels

6. Inferior Mediastinum Posterior: Esophagus Thoracic duct
Aorta and branches
Vagus nerves
Sympathetic trunks
Azygos system of veins

7. SUPERIOR MEDIASTINUM

8. Thymus Occupies superior mediastinum on either side of the midline.
Behind manubrium.
Covered by converging pleura of the lungs.
Involutes with fat after puberty.

9. Thymus Blood supply: Venous drainage:
Anterior mediastinal arteries from internal thoracic artery.
Inferior thyroid arteries from subclavian artery.
Venous drainage:
Into left brachiocephalic vein.

10. Thymus
Innervation:
Vagus nerve.
Cardiac sympathetic plexus.

11. Middle Mediastinum (inferior)
Pericardium:
Encloses heart.
(Fig. 1.35, p 137).

12. Middle Mediastinum (inferior)
Pericardium:
Visceral (serous) (Fig 1.37, p 139):
= epicardium.
Arterial mesocardium.
Venous mesocardium.
Transverse sinus:
Space between arterial and venous mesocardium.
Oblique sinus:
Space between right and left pulmonary veins.

13. Middle Mediastinum (inferior)
Pericardium:
Pericardial cavity.
Parietal (serous):
Fused to fibrous pericardium.
Fibrous:
Fused with central tendon of diaphragm:
Pericardiacophrenic ligament.
Fused with sternum:
Superior and inferior sternopericardial ligaments.

14. Middle Mediastinum (inferior)
Pericardium:
Blood supply (Fig. 1.38, p 139):
Pericardial arteries.
Pericardiacophrenic arteries.
Musculophrenic arteries.
Nerve supply:
CN X.
Phrenic nerve.
Sympathetic trunk.

15. POSTERIOR MEDIASTINUM

16. Esophagus From base of neck to:
Left of midline to:
Midline to:
Left of midline.
Passes through diaphragm at level of T10.
Lies:
Behind trachea.
In front of vertebral column.

17. Esophagus Blood Supply
Bronchial artery.
Thoracic aorta.
Left gastric artery.
Left inferior phrenic artery.

18. Esophagus Innervation
Esophageal plexus:
Continuation of posterior pulmonary plexus.
Formed by right and left vagus nerves:
Right vagus nerve  posterior vagus nerve.
Left vagus nerve  anterior vagus nerve.

19. Esophagus Innervation
Upper third:
Voluntary muscle.
Innervated by recurrent laryngeal nerve.
Lower two-thirds:
Involuntary muscle.
Innervated by vagus and sympathetic chain.

20. Left Thoracic duct Arises from cisterna chyli:
At union of right and left lumbar trunks.
Begins on the front of vertebral body T-12 or L-1.
Runs up through the thorax along the front of the vertebral column.
At first it lies to the right of midline.

21. Left Thoracic duct
It moves over to the left side when it reaches level T-5.
Receives most of lymph from body below diaphragm.
Drains left side of thoracic cavity and part of right.

22. Left Thoracic duct
Receives lymph from left internal jugular lymph trunk.
Receives lymph from left subclavian lymph trunk.
Empties into venous system at junction of:
Left internal jugular vein.
Left subclavian vein.

23. Right Thoracic duct
Drains upper right thoracic cavity, right upper extremity, and right side of head and neck.
Empties into venous system at junction of:
Right internal jugular vein.
Right subclavian vein.

24. Thoracic Sympathetic Chain
Lies against neck of ribs and costovertebral junctions.
12 thoracic ganglia pairs:
First one often fused with inferior cervical ganglion:
Referred to as stellate ganglion collectively.

25. Thoracic Sympathetic Chain
Cervical ganglia:
Superior.
Middle.
Inferior.

26. Thoracic Sympathetic Chain
The preganglionic sympathetic supply to the thoracic viscera are from T1–5.
The postganglionics are from:
Superior, middle, and inferior cervical ganglia.
T1-T5 paravertebral ganglia.
They exit the chain as direct fibers and travel downwards to enter the thorax:
As cardiopulmonary splanchnic nerves.

27. Thoracic Sympathetic Chain
The cardiopulmonary splanchnic nerves travel on their own and do not accompany other nerves or vessels.
Function:
Coronary artery dilation.
Increase heart rate.
Bronchodilation.

28. Splanchnic Nerves
Composed of preganglionic fibers and visceral sensory fibers.
Supply abdominal viscera.
Synapse in prevertebral ganglia.
Refer in text to Figure 1.41, page 63.

29. Splanchnic Nerves Greater: Lesser: T5-T9. Synapses in celiac ganglion.
Synapses in the superior mesenteric ganglion.

30. Splanchnic Nerves
Least:
T12.
Synapses in the aorticorenal ganglion.

31. Vagus Nerve Cranial nerve X
Major parasympathetic supply to thoracic and abdominal viscera.

32. Course of Vagus Nerve Parallel to esophagus:
Innervates esophagus
Passes posterior to root of lung on each side.
Pierces diaphragm with esophagus.
Becomes gastric nerve.
Supplies viscera in thoracic cavity.

33. Vagus Nerve Branches Cardiac branches to cardiac plexus.
Pulmonary branches to pulmonary plexus.
Esophageal branches to esophageal plexus.

34. Vagus Nerve Branches Left recurrent laryngeal nerve from left vagus:
Hooks around arc of aorta to left of ligamentum arteriosum.
Right recurrent laryngeal nerve from right vagus:
Hooks around subclavian artery.
Therefore: arises in neck, not thorax.

35. Phrenic Nerve Arises in neck from:
Ventral rami of C3-5 (C4 = major contribution)
Passes anterior to pulmonary root on each side (only nerve to do so).
Sole motor innervation to diaphragm.
Sensory fibers to pericardium, mediastinal pleura, and pleural and peritoneal coverings of diaphragm.

36. Phrenic Nerve
Pain via phrenic nerves usually referred to base of neck and tip of shoulder.
Accompanied by pericardiacophrenic arteries.
Branches of internal thoracic arteries

37. Lymphatic Drainage 50 tracheobronchial lymph nodes :
Some of the largest lymph nodes in the body.
Include:
Paratracheal
Superior tracheobronchial
Inferior tracheobroncial
Bronchopulmonary
Pulmonary
Text: p 131, Fig. 1.32

38. Lymph Drainage of Thoracic Cavity
Parasternal nodes:
Lie behind sternum along course of internal thoracic artery.
Receive lymph from thoracic wall, upper anterior abdominal wall, and diaphragm.
Also receive significant amount of lymph from mammary gland.
Dump into parasternal lymph channel.

39. Lymph Drainage of Thoracic Cavity
Posterior intercostal nodes:
Lie in posterior intercostal space between heads of ribs.
Receive lymph from thoracic wall and paravertebral regions.
Drain into thoracic duct:
From left and lower right.
Drain into right lymphatic duct:
From upper right.

40. Lymph Drainage of Thoracic Cavity
Diaphragmatic nodes:
Lie on upper surface of diaphragm.
Receive lymph from diaphragm, pericardium, upper surface of liver.
Drain to parasternal and posterior mediastinal nodes.

41. Lymph Drainage of Thoracic Cavity
Posterior mediastinal nodes:
Lie along esophagus and descending thoracic aorta.
Brachiocephalic nodes:
Lie along brachiocephalic veins.

42. Lymphatic Drainage of Thorax
Lymph Trunks
Bronchiomediastinal lymph trunks receive lymph from:
Posterior mediastinal nodes
Brachiocephalic nodes
Tracheobronchial nodes
Parasternal nodes

43. Lymphatic Drainage of Thorax
Thoracic Duct
Begins in abdomen on right side of midline.
Receives most of lymph from body below diaphragm.
Drains left side of thoracic cavity and part of right.
Receives lymph from left internal jugular lymph trunk.

44. Lymphatic Drainage of Thorax
Thoracic Duct (cont.):
Receives lymph from left subclavian lymph trunk.
Empties into venous system at junction of:
Left internal jugular vein.
Left subclavian vein.

45. Lymphatic Drainage of Thorax
Right Lymphatic Duct:
Drains upper right thoracic cavity, right upper extremity, and right side of head and neck.
Empties into venous system at junction of:
Right internal jugular vein.
Right subclavian vein.