Quiz 3 - Mediastinum Flashcards Preview

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Flashcards in Quiz 3 - Mediastinum Deck (54):

three compartments of the thoracic cavity

2 pleural cavities and a central region called the mediastinum


borders of the mediastinum

superior: superior thoracic aperture
inferior: diaphragm

anterior: sternum
posterior: thoracic vertebrae

lateral: pulmonary cavities/lungs


transverse thoracic plane

-divides the mediastinum into superior and inferior portions by an imaginary line that passes thru the sternal angle anteriorly and the T4/T5 disc posteriorly


subdivisions of the inferior portion of the mediastinum


*it is divided into these parts by the pericardium! (membrane surrounding the heart)



-one of the most anterior structures in the mediastinum
-anterior to the great vessels and pericardium
-lymphoid organs involved with immune system T cell development
-primarily active in childhood but then undergoes "involution" and becomes mostly fat


major organ within the mediastinum

the heart, which is surrounded by the percardium


pericardium has both ______ and _____ layers

fibrous and serous


fibrous pericardium

-tough outer layer
-does not stretch
-fused to the diaphragm
-continuous with the tunica adventitia of the great vessels


serous pericardium

-2 layers
-visceral serous: applied to surface of heart (deepest of the layers); also known as the epicardium
-parietal serous: lines the internal surface of the fibrous pericardium


where are the visceral and parietal layers continuous?

-near the origins of the great vessels


superior limit of the pericardium

transverse thoracic plane



-visceral layer of serous pericardium
-outer layer of the heart wall


great vessels

-the large arteries and veins that are attached to the heart
-include: ascending aorta, pulmonary trunk, SVC, IVC, and pulmonary veins


superior vena cava (SVC)

-formed by the convergence of the left and right brachiocephalic veins
-enters right atrium of heart

**note that the right brachiocephalic vein is formed when the subclavian vein merges with the internal jugular vein


inferior vena cava (IVC)

-enters right atrium
-carries deoxy blood from lower half of the body by passing thru the diaphragm at the T8 level



-largest artery in the body
-arises from the left ventricle
-travels thru the thorax (where it has 3 parts) and abdomen


3 parts of aorta in the abdomen

1. ascending aorta
2. aortic arch
3. descending thoracic aorta


ascending aorta

-arises from the left ventricle
-immediately gives off the right and left coronary arteries
-ends at the transverse thoracic plane


aortic arch

-passes posterior to the left heart
-gives off three branches: braciocephalic trunk (which gives rise to the right common carotid and the right subclavian arteries), the left common carotid, and the left subclavian arteries
-becomes the descending aorta at the T4/T5 disc


aortic arch begins and ends at...?

-transverse thoracic plane


thoracic (descending) aorta

-begins at the transverse thoracic plane
-descends on the anterolateral aspect of the vertebral column on the left side of the body
-gives off numerous branches
-major branches: broncial arteries, esophageal arteries, and posterior intercostal arteries
-passes posterior to the diaphragm at the T12 level, where it becomes the abdominal aorta


pulmonary trunk (aka main pulmonary artery)

-arises from the right ventricle
-bifurcates into the right and left pulmonary arteries


right pulmonary artery

-posterior to the ascending aorta and SVC as it travels towards the right lung


left pulmonary artery

-travels anterior to the thoracic aorta


ductus arteriosus

-a channel that exists during fetal circulation between the pulmonary trunk and the aortic arch
-allows blood to bypass non-functioning lungs in the fetus


at birth, the ductus arteriosus closes and becomes fibrous, leaving a remnant called ________

-the ligamentum arteriosum, located in the mediastinum


area between the aortic arch and the pulmonary vessels

-aortopulmonary window


how many pulmonary veins are there?

-carry oxygenated blood from lungs to left atrium



-found posterior to the great vessels in the midline
-bifurcates into the primary (main) bronchi at T4


tracheobronchial lymph nodes

-found at the tracheal bifurcation


paratracheal lymph nodes

-found along the lateral aspect of the trachea



-located directly posterior to the trachea
-continuous with the pharynx superiorly and the stomach inferiorly
-exits the thoracic cavity thru a hole in the diaphragm (the esophageal hiatus) at T10


unlike the trachea, the esophagus is found in _____

-both the superior and inferior mediastina


primary structures remaining in the posterior mediastinum after removing the esophagus and thoracic aorta

-azygos system of veins
-thoracic duct
-components of the autonomic system (sympathetic trunks)


azygos venous system

-posterior mediastinum
-receives drainage from the thoracic wall (primarily from posterior intercostal veins) as well as from veins of the viscera (e.g. esophageal and mediastinal veins)
-variations normal and common


azygos vein typically travels where?

-on the anterolateral aspect of the vertebral column on the right side of the body


accessory hemiazygos and hemiazygos veins travel where?

-anterolateral aspect of vertebral column on the LEFT side of the body
-drain into the azygos vein via branches that cross the midline


azygos vein drainage

superiorly: into SVC
inferiorly: connections with IVC in abdomen

-serves as a collateral channel if IVC blocked


thoracic duct

-largest lymphatic vessel in the body; receives lymph from the entire lower half of the body and ULQ and returns fluid to the venous system
-begins in upper abdomen as a dilation called the cisterna chyli
-in the mediastinum, it travels on the anterior aspect of the vertebral column, just to the right of the thoracic aorta, and to the left of the azygos vein
-terminates by merging with the venous system at the junction of the left internal jugular and left subclavian veins


lymph from RUQ

-drains into the right lymphatic duct


sympathetic trunks

-extend from the base of the skull to the coccyx
-in the thorax, they travel just lateral to the vertebral column anterior to the ribs
-various branches leave the sympathetic chain ganglia in the thorax


white and gray rami communicantes

-connect the sympathetic trunks to the spinal nerves
-emerge from the posterolateral parts of the ganglia


cardiac nerves

-emerge from the anteromedial parts of the cervical and upper thoracic sympathetic ganglia
-contain post-ganglionic sympathetic neurons that innervate the viscera of the thorax (not just the heart!) by traveling thru the thoracic visceral plexus


visceral nerves in the thorax (like the cardiac nerves) are distributed to their targets by traveling through a plexus that surrounds the thoracic viscera. what are the three major subdivisions of this visceral plexus?

1. cardiac plexus: found on the superficial and deep aspects of the aortic arch
2. pulmonary plexus: surrounds the tracheal bifurcation and primary bronchi
3. esophageal plexus: surrounds the esophagus


thoracic splanchnic nerves

-emerge from the anteromedial parts of the T5-T12 sympathetic ganglia
-contain pre-ganglionic sympathetic neurons that innervate viscera in the abdominal and pelvic cavities
-just traveling thru the thoracic without innervating anything

there are 3:
1. greater splanchnic: T5-T9
2. lesser splanchnic: T10-T11
3. least splanchnic: T12


phrenic nerves

-originate C3-C5 ventral rami
-enter mediastinum thru the superior thoracic aperture, travel ANTERIOR to the roots of the lungs and descend to the diaphragm along the lateral aspects of the pericardium
-provide somatic motor fibers to the diaphragm
-convey somatic sensations from the central part of the diaphragm, fibrous and parietal serous pericardium, mediastinal pleura, and the central part of the diaphragmatic pleura


pericardiacophrenic vessels

-travels with the phrenic nerve and provide blood to the pericardium and diaphragm


vagus nerves

-arise from the brainstem
-travel in the neck near the carotid arteries
-enter the thorax via the thoracic aperture
-POSTERIOR to root of lung (unlike phrenic nerves!) before entering the esophageal plexus


right vagus nerve

-travels along the lateral aspect of the trachea
-POSTERIOR to root of lung (unlike phrenic nerves!)
-enters esophageal plexus on the posterior part of the esophagus


left vagus nerve

-travels on the anterolateral surface of the aortic arch
-is in contact with the aortic arch
-POSTERIOR to root of lung (unlike phrenic nerves!)
-enters esophageal plexus on the anterior part of the esophagus


branches of the vagus nerves into visceral plexuses that innervate heart, bronchial tree, and esophagus

-contain parasympathetic neurons and visceral afferent neurons
-parasympathetic neurons decrease HR, constrict bronchial tree, stimulate peristalsis and the secretion of mucous in the esophagus.
-afferent neurons convey sensations of stretch from the lungs, pain from the heart, and participate in visceral reflexes


after traveling through the esophageal plexus, the vagus nerves do what?

-regroup as the anterior and posterior vagal trunks that travel through the diaphragm with the esophagus


left recurrent pharyngeal nerve

-branch of the vagus nerve that arises near the arch of the aorta
-travels thru the aortopulmonary window posterior to the ligamentum arteriosum, and ascends back into the neck along the lateral aspect of the trachea
-innervates portions of the larynx (e.g. somatic efferent fibers to muscles of the larynx)

***compression of this nerve by an aortic aneurysm or other mass can produce hoarseness of the voice!!!


right recurrent laryngeal nerve

-travels around the right subclavian artery in the neck
-is NOT in the mediastinum!!!