Thorax 10: Superior, Anterior, Posterior Mediastinum Flashcards
Superior mediastinum
The top section of the mediastinum, running from the superior thoracic inlet to the transverse thoracic plane
Transverse thoracic plane
The plane at the sternal angle
What are the structures found in the superior mediastinum?
Thymus, trachea, esophagus, brachiocephalic veins, SVC, aortic arch, brachiocephalic trunk, left subclavian and common carotid arteries; vagus nerve, phrenic nerve, cardiac plexus, left recurrent laryngeal nerve, thoracic duct, left superior intercostal vein
Thymus
A fat lymphoid organ of loosely organized collection of interconnected lymphoid lobules found in the anterior and superior mediastinum that mostly involutes in adults. It is the site of T-cell maturation
How are T-cells activated inside the thymus?
Thymic interdigitating cells present normal self components to maturing T-cells, which may activate some T-cells
Clonal deletion
The apoptosis of self-activating T-cells (T-cells that activate to self-antigens in the thymus)
How are T-cells activated outside the thymus?
They are exposed to antigens by antigen presenting cells
How does the thymus develop?
Pocketing of epithelium cells of the 3rd pharyngeal arches. Neural crest cells are involved
What is the role of the epithelium in thymus development?
They make the blood-thymus barrier and help T-cells develop
Thymus cortex
The outer layer of the thymus, formed by T-lymphocytes, thymic epithelial cells, and thymic dendritic cells
Thymus medula
The inner layer of the thymus
Hassal’s corpuscles
Onion-like structures in the thymus that are mostly degenerative
Thymus capsule
The layer on the outside of the thymus cortex
Why is the blood-thymus barrier important?
It keeps antigens out until T-cells are mature
Lymphatics in the thymus
There are none
Septae
Insertions into the thymus cortex where arteries enter the thymus
What type of cells form the blood-thymus barrier?
Epithelio-reticular cells
What nerves are found in the superior mediastinum?
Phrenic nerves, left vagus nerve, left recurrent laryngeal, right vagus nerve
Where is the left vagus nerve located?
Lateral to aortic arch
Where is the right vagus nerve located?
Dorsal to the aortic arch, on trachea and esophagus
Where is the left recurrent laryngeal nerve located?
Medial to aortic arch
What is found in the anterior mediastinum?
Thymus, sternopericardial ligaments, branches of internal thoracic vessels, lymph nodes
What is found in the posterior mediastinum?
Thoracic aorta and its branches, azygous system, sympathetic trunk, thoracic splanchnic nerves, vagus nerves, esophagus, thoracic duct, lymph nodes
With regards to the spinal cord, where does the esophagus run?
C6 - T11
Where does the esophagus enter the thoracic cavity?
Superior thoracic aperture
Where does the esophagus leave the thoracic cavity?
Esophogeal hiatus of the diaphragm (at T10)
What innervates the esophagus
Esophageal plexus
What supplies blood to the esophagus?
Esophageal branches of the aorta
What is the venous drainage of the esophagus?
Azygous veings; left gastric vein in the abdomen
From top to bottom, what are the four impressions on the esophagus?
Aortic arch, left main bronchus, left atrium, diaphragm
Of the vagus nerves, which one is posterior to the esophagus and which one is anterior?
Left is anterior and right is prosterior
What sympathetic nervs go to the esophagus?
Sympathetic nerves starting at T1-T5
What are the main branches of the thoracic aorta?
Pericardial, bronchial, esophageal, prosterior intercostal, subcostal , superior phrenic
Artery of Adamkiewicz
Largest anterior medullary feeder artery to the anterior spinal artery; it is the most important supply to the lower thoracic spinal cord
Azygous vein
A vein that originates in the abdomen on the right side and drains to the vena cava by arching over the root of the right lung
Hemiazygous vein
A vein on the lower left side of the thoracic cavity that originates in the abodem. It drains into the azygous vein at T9
Accessory hemiazygous vein
A vein on the upper left side of the thoracic cavity that drains into the azygous vein at intercostal spaces 5-8
What is the order of tumor spread from the lungs to other organs?
Segmental bronchi -> lobar bronchi -> interlobal bronchi -> hilar bronchi -> mediastinal nodes -> supraclavicular and sternal notch nodes
Where is the cardiac plexus located?
Anterior to the bifurcation of the trachea, posterior to the aortic arch, superior to the pulomary trunk
Where is the pulmonary plexus located?
Anterior and posterior to the roots of the lungs
What types of nerve innervate the lungs?
Visceral motor and nonsensory visceral afferents
From outer to inner, what are the layers between the outside of the pericardium and the heart?
Parietal layer of serous pericardium -> fibrous pericardium -> pericardial cavity -> visceral layer of serous pericardium -> subepicardial fat -> myocardium -> endocardium
How do we count ribs?
We can’t palpate the first rib because it’s under the clavicle, so we start counting from the second rib
What is the surface projection of the apex of the heart?
5th intercostal space to the left at the midclavicular line
What is the surface projection of the the right atrium of the heart?
3rd costal cartilage, one finger to the right of the sternum
What is the surface projection of the left atrium of the heart?
2nd intercostal space on the left, midway to the midclavicular line
What is the surface projection of the right ventricle of the heart?
The junction of the 6th costal cartilage and the sternum
Where can we best hear the tricupsid valve?
Just to the left of the lower part of the sternum near the fifth intercostal space
Where can we best hear the mytrial valve?
Just over the apex of the heart; at the 5th intercostal space to the left at the midclavicular line
Where can we best hear the pulmonary valve?
Over the medial end of the left second intercostal space
Where can we best hear the aortic valve?
Over the medial end of the right second intercostal space
What is the surface projection of the apex of the pleural sac?
Just above the median third of the clavicle
Where does the pleural sac end on the midclavicular line?
Rib 8
Where does the pleural sac end on the midaxillary line?
Rib 10
Where does the pleural sac end on the spine?
Rib 12
Where does the lung end during quiet respiration on the midclavicular line?
Rib 6
Where does the lung end during quiet respiration on the midaxillary line?
Rib 8
Where does the lung end during quiet respiration on the spine?
Rib 10
