Superior and Posterior Mediastinum Flashcards
What are the contents of the superior mediastinum from anterior to posterior?
Thymus Great vessels (veins then arteries) Vagus and phrenic nerves Left recurrent laryngeal nerve Cardiac pulmonary plexus Trachea Esophagus Thoracic duct Prevertebral muscles
The great vessels are the second most anterior structures in the superior mediastinum after the thymus. What great vessels exist in this compartment?
Brachiocephalic veins
Superior vena cava
Arch of the aorta with its 3 branches: brachiocephalic trunk, left common carotid a., left subclavian a.
Describe the location of the posterior mediastinum based on vertebral level and surrounding structures
Anterior to T5-T12, posterior to the pericardium, superior to the diaphragm, and medial to the pleural cavities
What are the contents of the posterior mediastinum?
Thoracic (descending) aorta Thoracic duct Lymph nodes Azygous and hemiazygous veins Esophagus Vagus nerve Esophageal plexus Thoracic sympathetic trunks Thoracic splanchnic nerves
What are the 4 major landmarks of the superior mediastinum?
Manubrium of sternum
Body of sternum
Blood vessels around manubrium
Thymus gland
The manubrium of the sternum is a superior mediastinal landmark. Which part of the manubrium corresponds to T2 vertebrae in men and T3 in women?
Suprasternal (jugular) notch
One of the landmarks for the superior mediastinum is the body of the sternum. The sternal angle connects to the second costal cartilage laterally. What is this a landmark for?
Bifurcation of the trachea and beginning of the aortic arch
What blood vessels can be found using the manubrium of the sternum as a landmark in the superior mediastinum?
Arch of the aorta
Right and left brachiocephalic veins
Brachiocephalic trunk, right subclavian vessels, common carotids
What superior mediastinal landmark is found behind the manubrium and body of the sternum?
Thymus gland
The cardiac and pulmonary plexus include the ______ nerves which run anterior to the roots of the lungs.
The ______ nerves run posterior to the root of the lung and give off the ________ nerve which hooks around the ligamentum arteriosum.
Phrenic
Vagus; left recurrent laryngeal
At what spinal cord levels would you find the sympathetic preganglionic cells of the cardiac and pulmonary plexus? Where are the postganglionics?
T1-T4/5; postganglionics in sympathetic chain
T/F: parasympathetic preganglionic fibers of the cardiac and pulmonary plexus are from the phrenic nerve
False; from the vagus nerve
Where would you find postganglionic parasympathetic fibers of the cardiac and pulmonary plexus?
Heart: Ganglia in epicardium/inner aortic arch
Lungs: small ganglia along bronchiolar tree
The usual pattern of branches of the aortic arch is present in 65% of people. What is the usual pattern?
Brachiocephalic trunk
Left common carotid a.
Left subclavian a.
Variations in the origin of the branches of the aortic arch are fairly common. In 27% of people, the left common carotid artery originates from the __________
Brachiocephalic trunk
Variations in the origin of the branches of the aortic arch are fairly common. A brachiocephalic trunk fails to form in approximately 2.5% of people. What happens in this case?
Each of the 4 arteries (right and left common carotid and subclavian arteries) originate independently from the arch of the aorta
Variations in the origin of the branches of the aortic arch are fairly common. In addition to the normal pattern, the _______ artery originates from the arch of the aorta in 5% of people
Left vertebral
T/F: both right and left brachiocephalic trunks originate from the aortic arch in approximately 1.2% of people
True
A __________________________ artery sometimes arises as the last (most left-sided) branch of the arch of the aorta. This artery crosses posterior to the esophagus to reach the right upper limb and may compress the esophagus, causing dysphagia
Retro-esophageal right subclavian
Variations in the origin of the branches of the aortic arch are fairly common. An accessory artery to the thyroid gland, the _________ artery, may arise from the arch of the aorta or the brachiocephalic artery
Thyroid ima
What are some anomalies that may occur with the aortic arch itself?
Right arch of the aorta (curves over root of right lung and passes inferiorly on right side)
Double arch of the aorta (forms vascular ring around esophagus and trachea, may cause compression)
What aortic branches are present in the posterior mediastinum?
Superior phrenic aa. Posterior intercostal aa. Esophageal aa. Bronchial aa. Tracheal aa. Supreme intercostal aa.
What veins are found in the superior mediastinum?
Brachiocephalic vv. Superior vena cava Subclavian v. Jugular v. Supreme intercostal v.
What veins are found in the posterior mediastinum?
Azygous v.
Hemiazygous v.
Accessory hemiazygous v.
Posterior intercostal v.
What are the 3 primary sources of arterial supply to the diaphragm?
Internal thoracic arteries
Thoracic aorta
Abdominal aorta
The 3 primary sources of arterial supply to the diaphragm include the internal thoracic arteries, the thoracic aorta, and the abdominal aorta.
What arteries come off the internal thoracic arteries to supply the diaphragm?
Musculophrenic aa.
Pericardiacophrenic aa.
The 3 primary sources of arterial supply to the diaphragm include the internal thoracic arteries, the thoracic aorta, and the abdominal aorta.
What arteries come off the thoracic aorta to supply the diaphragm?
Superior phrenic aa.
The 3 primary sources of arterial supply to the diaphragm include the internal thoracic arteries, the thoracic aorta, and the abdominal aorta.
What arteries come off the abdominal aorta to supply the diaphragm?
Inferior phrenic aa. (Although these sometimes arise from celiac trunk)
The esophagus lies anterior to the bodies of ______ and ______ vertebrae.
It is divided into 3 parts ______, ______, and ________
Cervical; thoracic
Cervical (C6-T1), thoracic (T1-diaphragm hiatus), abdominal
The esophagus descends slightly to the right of the ______ and pierces slightly left through the ________
Aorta; diaphragm
What are the 4 constrictions of the esophagus?
Cricopharyngeus m. in cervical region
Aortic arch
Left bronchus
Diaphragm
The esophagus is pushed to the right by the descending aorta, then it crosses over the aorta, heading left to the esophageal hiatus in the diaphragm.
What happens as a bolus of food passes through?
A bolus of food passes down the esophagus, the aortic arch, left primary bronchus and the diaphragm may constrict it
[Foreign objects may lodge here and strictures may form]
What supplies innervation to the esophagus?
Esophageal plexus
What nerves contribute to the esophageal plexus?
Left vagus (anterior) and right vagus (posterior) nn.
Thoracic postsynaptic sympathetic nerves
Branches of the postsynaptic sympathetic nerves to the thoracic plexus form the ______ _______ _____
Thoracic sympathetic trunk
What nerves are involved in the thoracic sympathetic trunk?
Greater splanchnic nn.
Lesser splanchnic nn.
Least splanchnic nn.
________ splanchnic nerves are made up of presynaptic sympathetic fibers from T5-9 that gather and pass anteriorly through the diaphragm to relay in the celiac ganglion
Greater
_______ splanchnic nerves go from T12 through the diaphragm to the renal plexus
Least
_______ splanchnic nerves consist of presynaptic fibers for T10-11 that gather and pass into the abdomen to relay in the aorticorenal ganglion
Lesser
The _________________ drains lymph from the right side of the head, neck, upper limb, and thoracic wall before emptying into the ______________
Right thoracic duct; right subclavian vein
The ______________ drains lymph from the lower abdomen and limbs, pelvis, left side of head, neck, and thoracic wall before emptying into the __________________
Thoracic duct; left subclavian vein
What drains 75% of the lymph from the body?
Thoracic duct
The thoracic duct runs on the anterior face of vertebral bodies ________, posterior to the _________, and between the _____ vein and ____________ __________
T6-12; esophagus; azygous; descending aorta
Describe the course of the thoracic duct in the superior mediastinum
Deviates left and approaches the left from the posterior, and terminates near the junction of the internal jugular vein and subclavian vein
What terminates in the same location as the thoracic duct but on the right side?
Right lymphatic duct
Enlargement of the mediastinal lymph nodes (which may occur in conditions like lung cancer), can impinge on which nerves in the mediastinum? What might this cause?
Vagal nerves
Impinging on the left recurrent laryngeal nerve can cause hoarseness, disrupting speech
Which subdivision of the mediastinum is the smallest, lying between the body of the sternum and transversus thoracis mm anteriorly, and the pericardium posteriorly?
Anterior mediastinum
What are the contents of the anterior subdivision of the mediastinum?
Loose CT (sternopericardial ligaments)
Fat
Lymphatic vessels
A few LNs
Branches of the internal thoracic vessels
Inferior part of thymus (in infants and children)
The ______ constitutes the primary posterior relationship of the base of the heart
Esophagus
Describe the blood supply to the esophagus
Esophageal arteries (there are usually 2 but can be as many as 5), which branch from the descending aorta
The thoracic duct originates from the _____ ____ in the abdomen and ascends through the ____ ____ in the diaphragm
Cisterna chyli; aortic hiatus
What group of lymph nodes lies in the mediastinum posterior to the pericardium in relation to the esophagus and thoracic aorta? What do these receive lymph from and drain to?
Posterior mediastinal LNs
Receive lymph from esophagus, posterior aspect of pericardium and diaphragm, and middle posterior intercostal spaces
Drain to right or left venous angles via right lymphatic duct or thoracic duct
What venous system, located on each side of the vertebral column, is responsible for draining the back and thoracoabdominal walls and mediastinal viscera?
Azygous venous system
Where does the azygous vein, and its main tributary the hemiazygous vein, typically arise from?
“Roots” arising from posterior aspect of IVC and/or renal vein, which merge with the ascending lumbar veins
Describe the participation of the azygous venous system in a collateral pathway
Azygous venous system forms a collateral pathway between the SVC and IVC and drains blood from the posterior walls of the thorax and abdomen - thus bypassing the terminal portion of the IVC
What are the 3 major veins that drain into the azygous system?
Mediastinal vein
Esophageal vein
Bronchial vein
