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what is the mediastinum

midline partition that separates thee pleural cavities


where is the mediastinum

from the superior thoracic aperture to inferior thoracic aperture
between sternum anteriorly and thoracic vertebrae posteriorly


what happens at the superior thoracic cavity

airways enter and vein drains back to the heart


what is the role of the mediastinum

acts as a conduit for structures that pass through thorax and structures that connect thoracic organs to other body structures
2 way conduit - head and neck to chest cavity and in reverse
airway from superior to carina to lungs pharynx opening in nasal cavities through thorax and to abdomen, nerve control heart and lung from brain into pericardium and airways


what does a PA x ray mean

x ray go through back of body and detector is at the front


why is a PA x ray done

PA/AP give different size of organs
heart is anterior - if PA short distance to detector - little dispersion
if AP - big distance to detector= large dispersion


components of the mediastinum

trachea - C6-T4/5 from larynx to bifurcation into principle bronchi
oesophagus - from pharynx, muscular tube, pierce diaphragm T10
heart and pericardium
thoracic duct - lymphatic drainage (remove interstitial fluid and involved in metastatic disease)
nerves and great vessels


what is the larynx

air way in throat


what structures pass through the diaphragm and where

T8 - inf V C
10 - oesophagus
12 - aorta


what do 8 10 12 relate to in the chest

pleural cavity


what does 6 8 10 levels relate to in the chest

level lungs


where is the superior mediastinum

above sternal angle
from superior thoracic aperture


where is the inferior mediastinum

below sternal angle
above inferior thoracic aperture


what 3 parts make up the inferior mediastinum



middle mediastinum

has pericardial sac and heart


anterior mediastinum

anterior to heart


posterior mediastinum

behind pericardial sac and diaphragm
has nerves of SNS and veins that drain chest from abdomen to heart
has everything that moves from superior to inferior


what are the contents of the superior mediastinum

thymus - immunologically active, replaced by fat
phrenic nerves - contract diaphragm and provide sensation for pericardium and peritoneal lining (under diaphragm)
great veins
main lymphatic trunk
vagus nerves
great arteries
trachea and main bronchi
upper oesophagus


what are the great veins

superior vena cava (enter RA from above)
inferior vena cava (enter RA from below - through the central tendon of diaphragm T8!)


describe the superior vena cava in situ

offset to the R
formed by the union of R and L brachiocephalic veins
brachiocephalic vein forms internal jugular veins (drain head) and subclavian veins (drain arms)


what is the path of the L brachiocephalic vein

crosses at sternoclavicular joint, and manubrium and 1st rib posterior to manubrium to reach R brachiocephalic vein to form the SVC
the veins move anterior to the arteries


describe the azygous vein

largest on R
anterior intercostal vessels drained into internal thoracic vessels
drains posterior wall of thorax and abdomen
hemiazygos and accessory hemiazygos on L - drain chest wall
arches over the R lung root
runs behind SVC carrying deoxygenated blood
drains into the superior VC


inferior vena cava in situ

little in thorax
goes straight into the RA
most is in the abdomen


where does the L superior intercostal vein drain into

brachiocephalic vein


arteries in superior mediastinum

ascending aorta - come superior from the heart
arch of aorta - move superiorly, laterally and down
descending aorta - down back, diaphragm and to abdomen at T12


ascending aorta

R and L coronary arteries
supply heart muscle with the most oxygenated blood
terminal arteries
may need bypass (from leg vein)


aortic arch

brachiocephalic trunk - R common carotid and R subclavian arteries
L common carotid
L subclavian artery - under clavical - to axilla and upper limbs


relation of aortic arch to pulmonary branch



relation of aorta nad arteries to airways

aortic arch anterior to trachea
arches over L main bronchus at lung root
trachea is behind and between the brachiocephalic and L common carotid arteries
azygous vein runs along the back of the chest - arch over airways over lung root into back of superior vena cava


explanation of the points components pass through diaphragm

aorta almost vertical at the back - pass more posteriorly and so at a lower vertebral level than oesophagus and IVC
then oesophagus
than IVC