1. Mediastinum

2. Mediastinum
central structures between two pleural sacs, sternum & vertebral bodies

3. Mediastinum
Region
1. superior mediastinum: behind manubrium (pleura are apart here)
thymus gland - most anterior structure, behind manubrium
in front of brachiocephalic vein, aortic arch
slowly shrinks w age (largest in childhood), replaced largely by adipose
2. inferior: separation from superior is at line between sternal angle & intervertebral disc 4- 5 a. anterior - in front of pericardium (thin space) b. middle - contains pericardium, phrenic nerves, blood vessels c. posterior - behind pericardium

7. Vessels
arch of the aorta - opposite arch of azygos, just superior to root of left lung
thoracic aorta: ascending - arch - descending aorta - posterior to root of right lung, arteries exit superiorly from arch:
brachiocephalic artery
brachiocephalic artery then divides to right common carotid and right subclavian aretry
Left common carotid
Left subclavian artery

8. 1. Brachiocephalic Artery 2. Carotid Artery, Left 3
1. Brachiocephalic Artery  2. Carotid Artery, Left  3. Subclavian Artery, Left  4. Aortic Arch  5. Ascending Aorta  6. Pulmonary Trunk  7. Pulmonary Artery, Left  
8. Pulmonary Vein, Left  9. Atrim, Left  10. Bicuspid Valve 11. Aortic Semilunar      Valve 12. Ventricle, Left 13. Interventricular      Septum 14. Ventricle, Right 15. Papillary Muscle 16. Chordae Tendinae 17. Tricuspid Valve 18. Atrium, Right 19. Pulmonary       Semilunar Valve 20. Superior Vena Cava

10. Veins
superior & inferior vena cava - entering the right atrium = junction of brachiocephalics
brachiocephalic veins - continuous with superior vana cava superiorly, behind sternoclavicular joint
a. combination of subclavian & internal jugular veins
b. internal thoracic veins also drain into brachiocephalics

13. Blood vessels Pulmonary trunk
Pulmonary trunk: short, just left of aortic arch - branches to Right, Left pulmonary artery - ligamentum arteriosum - residual of ductus arteriosum - connects to aorta in fetal circulation
Azygos vein

17. Other structures Other structures in mediastinum
Trachea - behind right brachiocephalic vein
Esophagus - behind trachea

18. Nerves
phrenic nerve: in mediastinal pleura on each side, anterior to roots of lungs
anterior to subclavian artery, parallels internal thoracic artery
adjacent to brachiocephalic veins, superior vana cava or aorta, pericardium; to diaphragm
vagus nerves: posterior to phrenics
Right vagus - between brachiocephalic artery & vein
Left vagus - between left common carotid & subclavian artery
recurrent laryngeal branch of left vagus - curls under aortic arch behind ligament arteriosum
recurrent laryngeal branch of right vagus - curls under the subclavian artery 

22. Plexus from Vagus Cardiac plexus: 2 portions
superficial - just under aortic arch; & deep - posterior to arch, anterior to trachea (gets most branches) comprised of branches of sympathetic trunks:
3 cervical cardiac branches - from neck, thru inlet to superior Mediastinum
several thoracic branches
Pulmonary plexuses: 4 - R & L anterior & posterior
in front & behind pulmonary artery on each side, at root of lungs
from there into lungs
nerve filaments arise as branches from cardiac plexus
Coronary plexus - nerve filaments also come from cardiac plexus         - to heart, follow coronary arteries

23. Pericardial Sac Serous Pericardium - serous membrane - double layer
a. visceral pericardium - forms epicardium - outer covering of heart
b. parietal pericardium - thicker, tougher than pleura   
c. pericardial cavity
Fibrous pericardium - dense fibrous CT - fused with parietal serous pericardium continuous with deep fascia of neck also attaches to diaphragm below & to esophagus & aorta posteriorly

24. Pericardiocentesis