Mediastinum Flashcards
Mediastinum:
- Location
- Borders
- In the center between two pleural cavities (at sternum), but also projects left of sternum to include heart
anterior: sternum
posterior: thoracic vertebrae
superior: superior thoracic aperture
inferior: diaphragm
What are the subdivisions of the mediastinum?
superior and inferior
inferior includes anterior, middle=pericardium, and posterior
Transerse thoracic plane
- Location
- What does it separate
- Sternal angle anteriorly to 4/5th intervertebral disc posteriorly
- Divides mediastinum into superior and inferior levels
- Also divides the aortic arch into its ascending and descending branches
- Defines superior limit of the pericardium
What is the most anterior structure in the mediastinum? What does it do?
Thymus (not thyroid)
Lymphoid organ that makes T cells - large in children
involution at puberty = becomes fat
What are the four layers of the pericardium?
- Fibrous pericardium
- Parietal serous layer
- Pericardial cavity
- Visceral serous layer = epicardium
What are special features of the fibrous pericardium?
- Tough outer layer = does not stretch
- Fused to diaphragm and tunica adventitia of the great vessels
Which two layers is the pericardial cavity between?
Parietal and visceral layers of serous pericardium
Inferior vena:
- blood from where
- where does it enter the heart
3, Where does it pierce the diaphragm
- deoxy blood from lower half of the body
- inferior right atrium
- T8
What are the immediate bracnhes of the aortic arch?
- brachiocephalic
- left common carotid
- left subclavian
Descending aorta
- Where does it begin and end
- Name the major branches
- Begins at the transverse thoracic plane, ends at the T12 level of the diaphragm
- bronchial arteries, esophageal arteries, posterior intercostal arteries
Pulmonary trunk
- What is it?
- Where are its branches?
- main pulmonary artery from the right ventricle
- Right pulmonary artery = posterior to ascending aorta and SVC
- Left pulmonary artery = anterior to thoracic aorta and SVC
What is the function of the structure?
Ligamentum arteriosum - remnant of ductus arteriosus
Trachea
- What is it posterior to?
- Where does it bifurcate into the primary bronchi?
- great vessels
- T4 level
Tracheal lymph nodes
What are the openings in the diaphragm and what passes through each?
I 8 10 Eggs At 12
I 8: IVC at T8
10 Eggs: Esophagus at T10 (with vagus nerve)
At 12: Descending aorta at T12 (with thoracic duct)
What is the esophagus continuous with?
Pharynx and stomach
Azygous system
- Right vs. Left of vertebral column
- What does it drain from
Right: azygous vein
Left: accessory hemiazygous vein
Drains from posterior intercostal veins
Azygous vein
- Drain from
- drain to
- Veins from thoracic wall (posterior intercostal) and visceral veins
- drains into SVC superiorly and IVC inferiorly (in abdomen) -> serves as collateral if IVC is blocked
What is the largest lymphatic vessel in the body
Thoracic duct
Thoracic duct
- Drain from
- Where does it begin
- Drain to
- receives lymph from the entire lower body and upper left quadrant
- Begins as the cisterna chyli (major collecting point for lymph flow below abdomen)
- Drains to venous system: left internal jugular and left subclavian veins
Cadaver image
Thoracic visceral plexus
- What innervates it
- What are its subdivisions and it locations
1. Vagus nerve (parasympathetics)
- Cardiac plexus (on aortic arch), pulmonary plexus (near tracheal bifurcation), esophageal plexus (on esophagus)
Thoracic Splanchnic nerves
- Vertebral level
- What does it innervate
- Divisions
- T5-T12 sympathetic ganglia
- Abdominal and pelvic cavities only (not thoracic)
- Greater splanchnic (T5-9), Lesser (T10-11), and Least (T12)
Where does the right lymphatic duct receive its lymph?
Right upper quadrant of body
What are the main nerves of the mediastinum?
- phrenic nerves
- vagus nerve
- left recurrent laryngeal nerve
Phrenic nerves
- function
- Vertebral level
- Where does it enter mediastinum
- what does it travel along
- Breathing (somatic efferent fibers to diaphragm)
- C 3,4,5 keeps the diaphragm alive
- superior thoracic aperture
- Runs down fibrous pericardium
What vessels supply the pericardium and diaphragm? What does it travel with?
Pericardiacophrenic vessels (travel with phrenic nerves)
Which nerve travels anterior to the root of the lung? Posterior?
Anterior: Phrenic nerve
Posterior: Vagus nerve
Vagus nerve
- function
- Vertebral level
- Where does it enter mediastinum
- what does it travel along
- PNS, visceral afferent fibers (to visceral plexuses), somatic efferent fibers (to larynx)
- Brainstem (CN X)
- Superior thoracic aperture
- Posterior to root of the lung
Right vs. Left vagus nerve
- Travel differences
- Relation to esophageal plexus
Right: travels along trachea, enters posterior part of esophageal plexus
Left: travels along aortic arch, enters anterior part of esophageal plexus
Left recurrent laryngeal nerve
- From what major nerve
- Where does it arise
- Function
- Places of injury
- Vagus nerve
- Near aortic arch, loops around aorta & posterior to ligamentum arteriosum
- somatic efferent fibers to larynx muscles
- tracheal-esophageal groove, aortic anerurism, inflammation of ligamentum arteriosum -> hoarseness of voice
Describe structures of mediastinum from anterior to posterior
Thymus -> Great vessels/Heart -> Trachea -> Esophagus -> Azygous system/Thoracic duct ->Symp trunk
Where is the right recurrent laryngeal nerve located?
Wraps under the subclavian artery (NOT in mediastinum)
