Mediastinum Flashcards
What divides the mediastinum into superior and inferior mediastina?
The transverse thoracic plane, TPP
What are the compartments of the inferior mediastinum?
Anterior, middle and posterior mediastina
Where can the transverse thoracic plane of Ludwig be found?
Runs thought the level of the manubrio-sternal angle of Louis and T4 intervertebral disc
What are the ABC’s of the TTP?
Arches: Aortic arch on the left, Azygous on the right
Bifurcations: tracheal and pulmonary trunk Bifurcations
Change in direction: esophagus and thoracic duct
What other structures can be found at the TTP besides the ABCs?
Tracheobronchial lymph nodes
Cardiac and pulmonary plexuses
Ligamentum arteriosum
Where is the superior mediastinum located?
Between the TTP and superior thoracic aperture
Where is the Thymus gland located?
In the inferior part of the neck and anterior part of the superior mediastinum, especially in children whom it is relatively large and readily recognizable on a chest X-ray
When does the thymus undergo involution?
After puberty
What is the thymus gland for?
Training of T-lymphocytes as part of cell-mediated immunity (CMI)
Where does the thymus receive its vasculature?
Mainly from branches of the internal thoracic artery
Where does the thymus gland’s lymph nodes drain into?
Para sternal nodes
What carcinoma is commonly seen in the thymus gland and with what disease is it commonly seen?
Malignant thymoma
Myasthenia gravis
What is the relationship between thymoma and myasthenia Travis?
50% of cortical thymoma patients develop myesthenia graves
15% of myasthenia gravis patients develop thymoma
What is myasthenia gravis?
An autoimmune neuromuscular junction disease caused in 85% of cases by acetylcholine receptor (AChR) antibodies
What forms the brachiocephalic vein?
Internal jugular and subclavian veins
How is the superior vena cava (SVC) and at what level is it found?
The left brachiocephalic vein crosses the midline to join the right brachiocephalic being to form the SVC at the level of the first chondrosternal joint, postero-lateral to the right margin of the sternum
When does the SVC receive the azygous vein?
At the level of the second chondrosternal joint
Where does the SVC end?
At the right atrium at the level of the 3rd sternochondral joint
Where does the SVC collect blood from?
Upper half of the trunk, upper limbs and head/neck
What does compression of the SVC lead to?
Superior mediastinal/VC syndrome
Symptoms: blu head, neck and upper limbs with engorged superficial veins
What are the arteries of the superior mediastinum?
Upper part of the arch of the aorta (and branches), namely the Brachiocephalic trunk, left common carotid and left subclavian arteries
Where does the arch of the aorta start?
Posterioylteral to the second sternochondrial joint at the level of the TTP)
Where is the concavity of the arch of the aorta?
TTP
What are the 3 bregular branches of the arch of the aorta
Brachiocephalic trunk, left common carotid artery and left subclavian artery
What is the first branch of the aortic arch?
Brachiocephalic trunk which arises from the apex of the arch anterior to the trachea
What does the brachiocephalic trunk divide into and where?
Behind the first venous angle ( behind the right sternoclavicular joint) into the right subclavian and right common carotid arteries
What do the branches of the brachiocephalic trunk supply?
Right subclavian: the upper limb
Right common carotid arteries: head and neck region
Where does the left common carotid artery arise from?
The second branch of the aortic arch from its convex surface (on the left side of the brachiocephalic trunk, trachea and esophagus)
What path does the left common carotid artery follow?
It runs upwards and to the left of the trachea to enter the root of the neck behind the left sternoclavicular joint
Where does the left subclavian artery arise from?
The aortic arch on the descending part of the arch, just to the left of the left common carotid artery
What is the path of the left subclavian artery and what does it supply?
It runs upward along the left side of the trachea and esophagus to enter the root of the neck by arching over the lun apex, to supply branches to the neck, thorax and upper limb.
What does the left subclavian artery become and where?
The axillary artery at the lateral margin of the first rib
What are the branches of the Left subclavian artery?
VIT C and D
Where is the trachea located?
Anterior to the esophagus ad posterior to the thyroid gland in the neck
Where does the trachea bifurcate and into what?
Below the carina into the left and right main stem bronchi at (T4 IVD,TTP, sternal angle)
What is tracheomalacia?
A disorder in infants in which the trachea lacks structural support so that the negative airway pressures generated during inspiration causes the trachea to collapse.
Results in: a strider during inspiration (high-pitched whistling sound)
How is the esophagus different than other digestive organs?
It lacks serosa
What supplies blood to the esophagus?
Inferior thyroid
Bronchial arteries, DTA
Left gastric
Inferior phrenic arteries
Where do the esophageal veins empty into?
Portal venous system
What is the MC cause of portal hypertension?
Cirrhosis of the liver in chronic alcoholics
Schistosomiasis in the tropics
Esophageal varices are dilated veins of the esophagus commonly seen in what conditions?
Portal hypertension
What are the 5 nerves of the superior mediastinum?
Two vagus
Two phrenic
left recurrent laryngeal nerve
Where is the left recurrent laryngeal nerve given off the vagus nerve?
Between the last two arteries of the arch of the aorta (left carotid and left subclavian)
What does the phrenic nerve innervate?
3 P’s (pleura, pericardiu and peritoneum)
Thoracic part of the thoracic diaphragm
Where does the right phrenic artery lie?
To the right side of the brachiocephalic vein, superior vena cava, right atrium, inferior vena cava before entering the abdomen through the inferior caval opening
Where does the left phrenic nerve lie?
Between the left brachiocephalic vein and the last two branches of the aortic arch, on the left side of the left atrium and left ventricle before piercing the thoracic diaphragm near the cardiac apex
Where is the ascending aorta located?
Anterior to the mediastinum
Where does the ascending aorta come from?
At first behind the pulmonary trunk and to the left of superior vena cava then between the two before arching back towards the posterior mediastinum as the arch of aorta.
The arch and ascending aorta and their neighbors are covered by the inferior part of what gland?
Thymus gland
What does the posterior mediastinum contain
(Inferior)?
Posterior mediastinal lymph nodes
Thoracic duct
Sympathetic trunk Azygous system of veins Descending thoracic aorta Lymphatic trunk Esophagus
Where is the descending thoracic aorta located?
Left side of the vertebral column and thoracic duct, posterior to the esophagus, and anterior to the azygous veins. It passes behind the thoracic diaphragm at T12 (aortic hiatus) to enter the abdomen
What are the branches of the descending aorta?
Bronchial (2 Lt)
Esophageal
Subcostal (one on each side)
Tracheal
Pericardial
Intercostal
Mediastinal
Phrenic (Superior)
What accompanies the the descending aorta through the aortic hiatus at T12?
Thoracic duct and azygous vein
What is the largest lymphatic vessels in the venous system? (About 75% of drainage)
Thoracic duct
What does the thoracic duct drain?
Both halves of the body below the thoracic diaphragm and left side of the body above the thoracic diaphragm
What are the tributaries to the thoracic trunk in the thorax and in the abdomen?
Thorax: left jugular, left subclavian and left brnchomediastinal trunks
Abdomen: lumbar and intestinal lymphatic trunks
What makes up the azygous system of veins?
Azygous
Hemiazigous
Accessory hemiazygous
Where are the azygous system veins located?
Right side: azygous
Left side: hemiazygous and accosts hemiazygous
How does the sympathetic chain (splanchnic) leave the thoracic cavity?
By passing deep to the medial accurate ligament of the thoracic diaphragm
What do the upper 5 splanchnic nerves supply?
The thoracic viscera
