Mediastinum Flashcards
What are the boundaries of the mediastinum?
Superior: Thoracic inlet Inferior: Diaphragm Lateral: L. and R. pleural cavities Anterior: Sternum and CCs Posterior: T1 - T12
Primary divisions of the mediastinum and their borders:
- Superior mediastinum
(Separated by the transverse thoracic plane = T4/T5 to Sternal Angle) - Inferior mediastinum
a. Anterior (anterior to pericardial sac, posterior to body of sternum)
b. Middle (bounded by pericardial sac)
c. Posterior (anterior to T5 - T12), posterior to pericardial sac and diaphragm)
What connects the neck and the chest?
Superior mediastinum
What are the contents of the superior mediastinum?
- Thymus
- Great vessels (Brachiocephalic veins, SVC, aortic arch, brachiocephalic trunk, left common carotid artery, left subclavian artery, vagus nerve, phrenic nerve, cardiac plexus of nerves
- Trachea, Esophagus, left recurrent laryngeal nerve
- Thoracic duct and lymphatic trunks
- Level VII group of lymph nodes
- Parathyroid (ectopic)
Anterior to Posterior:
Thymus -> Veins -> Arteries -> Airway -> Alimentary Tract -> Lymphatic Trunks
From which pharyngeal arches did the parathyroid and thymus come from?
3rd and 4th Pharyngeal arch
Primary lymphoid organ located in the inferior part of the neck and anterior part of the mediastinum where T-lymphocytes mature.
Thymus
What is the blood supply of the thymus?
Anterior intercostal and anterior mediastinal branches of internal thoracic arteries
Enlarged thymus leading to obliteration of superior and anterior mediastinum. Motor issue wherein eyelids are nonfunctional in the afternoon.
Myasthenia gravis
Returns blood from all structures superior to the diaphragm except lungs and heart
Superior Vena Cava
Formed by the union of the internal jugular veins and subclavian veins at the level of the _____________.
Ends and enters right atrium at level of the ____________.
1st right costal cartilage
3rd right costal cartilage
Squeezing of the SVC due to a tumor causing an enlarged head and prominent veins in neck
SVC Syndrome
Remnant of the fetal ductus arteriosus
Ligamentum arteriosum
What lies above the plane of the sternal angle of Louis (2nd rib)?
Arch of the aorta
Where does the arch of aorta become the thoracic aorta?
After it passes the 2nd left rib
First and largest branch of the arch of aorta:
Brachiocephalic trunk
Brachiocephalic trunk divides into:
- Right common carotid artery
- Right subclavian artery
What arches around the right main bronchus?
Azygos vein
Phrenic nerve arises from:
C3, C4, and C5 of the cervical plexus
Phrenic nerve motor and sensory supply:
Motor: Diaphragm Sensory: - 1/3 of diaphragm (superior and inferior) - Pericardium - Mediastinal pleura
Extent of Trachea
C6 - T4 (Sternal Angle) then it bifurcates into right and left bronchi
Entrance of esophagus to diaphragm
Esophageal hiatus
Constrictions of the esophagus
15 - 23 - 40 cm from upper incisors
Where does the thoracic duct drain into?
Junction between IJV and subclavian vein
Anterior mediastinum boundaries
Superior: Superior mediastinum / sternal angle
Inferior: Diaphragm
Anterior: Body of sternum and transversus thorasis muscle
Posterior: Pericardium
What are the contents of the anterior mediastinum?
Fat, areolar tissue
Thymus
What are the content of the middle mediastinum?
Pulmonary veins, Pulmonary artery, Aorta, SVC and IVC
Base of the heart is fixed to the pericardial wall at the level of:
T5 - T8 / T6 - T9 (when standing)
Heart cannot expand because of pericardial sac being filled with fluid
Cardiac tamponade
Pain in the parietal pericardium can be felt in the neck due to which nerve?
Phrenic Nerve (C3 - C5)
Tough external layer which protects the heart against sudden overfilling
Fibrous pericardium
What are the attachments of the fibrous pericardium?
Superior: Tunica adventitia of great vessels
Inferior: Pericardiocophrenic ligament
Anterior: Sternopericardial ligament
Posterior: Posterior mediastinum
Composed of mesothelium, a single layer of flattened cells lining the fibrous pericardium and external surface of the heart
Serous pericardium
Layer of the serous pericardium that forms the epicardium, the outermost layer of the heart.
Visceral layer of the serous pericardium
Separates the two groups of great vessels (important during surgery): Pulmonary artery and aorta separated from SVC, IVC, and pulmonary veins
Transverse pericardial sinus
Arterial and venous supply of the fibrous and serous pericardium:
Pericardiophrenic artery and vein
Where does the descending aorta terminate?
T12
Bronchial arteries, esophageal artery, and the posterior intercostal arteries are branches of:
Thoracic Descending Aorta
Level of esophageal hiatus:
T10
What ascends in the posterior mediastinum between the thoracic aorta and azygos vein?
Thoracic Duct
What receives lymph from the esophagus, posterior aspect of the pericardium and diaphragm, and the middle posterior intercostal spaces?
Posterior mediastinal lymph nodes
What drains the back, thoracoabdominal walls, and mediastinal viscera?
Azygos system of veins
What receives blood from the 4th - 8th ICS?
Accessory hemiazygos vein
What receives blood from the inferior 3 posterior intercostal veins, the inferior esophageal veins, and several small mediastinal veins?
Hemiazygos vein
