Thorax III Flashcards
What are the boundaries of the superior mediastinum?
Sup - superior thoracic aperture
manubrium of sternum, 1st rib, 1st thoracic vertebrae
Post - thoracic vertebrae 1 - 4
Ant - manubrium of sternum
Lateral = lungs and mediastinum
Inf = transverse thoracic plane
T4/5 intervertebral disc - separates superior mediastinum to rest
What structures lie posterior and anterior to the sup mediastinum?
Post = sympathetic trunk Ant = remnants of thymus
What does the superior mediastinum contain?
Great vessels:
Arch aorta - brachiocephalic trunk, left common carotid, left subclavian
Returning brachiocephalic veins
Oesophagus
Phrenic and vagus nerves
What structures come off the arch of aorta?
- brachiocephalic artery
branches into right common carotid and right subclavian
Trunk passes posterior to the manubrium between trachea and right brachiocephalic veins - Left common carotid
- Left subclavian
List some variations of the arch of aorta
Left common carotid may come off the brachiocephalic trunk
Some people may fail to form a brachiocephalic trunk - so have a left vertebral artery (originates from arch)
or they have 2 brachiocephalic trunks - R+L
Few people have arch going over root right lung and passing inferiorly to the right (forms a right arch)
or have abnormal arch passing over root right lung, passes posterior to oesophagus to reach usual position on left
Describe the positioning of the right and left pulmonary arteries
Right pulmonary passes posterior to ascending aorta and SVC before entering root right lung
Left pulmonary artery runs below the aortic arch and anterior to descending thoracic aorta to enter root left lung
What is the ligamentum arteriosum?
Band of fibrous tissue connecting top of pulmonary bifurcation to bottom aortic arch
Remnant of artery patent before birth which diverted blood flow to lungs before baby begins to breathe
Identify between left pulmonary artery in root of lung and arch of aorta
What level does the descending thoracic aorta begin?
Describe its course
Begins at T4/T5 from arch of aorta
Descends into posterior mediastinum and passes through aortic hiatus of diaphragm at T12
What are the branches of the thoracic aorta?
Bronchial Oesophageal Pericardial Mediastinal Posterior intercostal (9) Subcostals Sup. phrenic arteries
What point do the right and left brachiocephalic veins join to form the SVC?
Inferior border of the 1st right costal cartilage
Describe the location of structures in the thorax
Most anterior and superior vessel in the mediastinum is brachiocephalic and subclavian veins
Behind have arch of aorta and branches
Middle = thorax
Behind thorax = oesophagus
Thoracic duct - arches over to come back into brachiocephalic vein
thoracic duct = drainage for lymphatic system
What does the azygous vein drain?
Drains posterior thoracic wall and runs over root of right lung
Provides potential connection between SVC and IVC
Arch of azygous leaves impression on right lung
Where does the azygous vein originate?
In the abdomen
Passes posteriorly, then anteriorly
Where does blood from the hemiazygous and accessory hemiazygous veins drain into?
Drain into azygous vein on right
Hemi and accessory act together to serve as left side equiv azygous vein
What do accessory hemi-azygous veins drain?
Middle, left and posterior intercostal veins
Drains 3-5 intercostal veins
At what level does the acccessory hemiazygous vein cross posterior to the aorta?
Level T7
What does the hemiazygous vein drain?
9-11 posterior intercostal veins and subcostal veins on left side
some oesophageal and mediastinal veins
What level does the hemiazygous vein drain into the azygous vein?
T8
Begins in abdomen and travels up
Forms H sign over vertebral bodies as crosses over to right
How do the hemiazygous and accessory hemiazygous drain into the azygous vein?
Drain separately Hemi - inferior Accessory - superior thoracic duct passes over them behind brachiocephalic and loop around
What level does the thoracic duct begin?
T12 - aortic hiatus of diaphragm
What does the thoracic duct drain?
Lymph from the body except for drainage from superior portion RHS (lung, chest, upper limb) - right lymphatic duct drains this into right subclavian
What is the cisterna chyli?
Dilated sac where lymph from middle portion and abdominal content collects
eg. lumbar lymph trunk (lower limbs), intestine
Runs along the aorta?
Describe the course of the thoracic duct
Lymph from the cisterna chyli drains into the thoracic duct - begins at T12
Continues superiorly where shifts left (T5) to be behind oesophagus
At level C7 drains in between left internal jugular vein and left subclavian vein to join systemic circulation
Describe the course of the right phrenic vein
Behind the clavicle
It descends lateral to the brachiocephalic vein and SVC
Runs anterior to root of right lung, across pericardium to diaphragm
Goes through the diaphragm with the vena cava
Describe the course of the left phrenic nerve
Descends along the left side of the left subclavian artery
Crosses left vagus nerve superficially as approaches aortic arch
Passes over intercostal vein in front of arch of aorta
Over the lateral, posterior aspect of the pulmonary trunk
Runs along anterior, lateral aspect borders of the pericardial sac to innervate diaphragm - attaches to it
Origin = C3,4,5
Describe the course of the right vagus nerve
Comes down inferiorly in the carotid sheath alongside the right common carotid
Passes anterior to the brachiocephalic trunk (right subclavian)
Runs posterior to the root of the right lung
Runs more latero-posteriorly along the oesophagus - to become the bulk of the posterior vagal trunk
Describe the course of the right recurrent laryngeal nerve
Branches off the right vagus nerve and loops posterior and inferior to the subclavian artery before going up to the larynx (along the tracheo-oesophageal groove)
What are the branches of the right vagus?
Oesophageal, pulmonary and deep cardiac plexus