Posterior Mediastinum

Gross Anatomy

Posterior Mediastinum

Anatomy Tables for Today's Topic

Nerves of the Thoracic Cavity
Arteries of the Superior and Posterior Mediastina
Veins of the Superior and Posterior Mediastina
Lymphatics of the Thorax
Viscera of the Superior and Posterior Mediastina

Nerves of the Thoracic Cavity

Nerve Source Branches Motor Sensory Notes
phrenic n. ventral primary rami of spinal nerves C3-C5 (cervical plexus) no named branches skeletal muscle of the respiratory diaphragm diaphragmatic pleura; some fibers contributed to the pericardium and to the adjacent mediastinal and costal pleurae phrenic n. crosses the anterior surface of the anterior scalene m.
splanchnic, greater thoracic neurons in the intermediolateral cell column of spinal cord levels T5-T9; the greater thoracic splanchnic nerve appears to arise by multiple contributions from the sympathetic trunk no named branches celiac ganglion; preganglionic fibers supply the adrenal medulla which releases epinephrine and norepinephrine into the blood pain from the abdominal viscera greater thoracic splanchnic n. passes through the crus of the respiratory diaphragm; postganglionic processes from the celiac ganglion spread down the aorta and distribute with its branches; they innervate the vascular smooth of these vessels and vascular smooth muscle of the organs supplied
splanchnic, least thoracic neurons in the intermediolateral cell column of spinal cord level T12 no named branches renal plexus pain from the kidney and suprarenal gland least thoracic splanchnic n.pass through the crus of the diaphragm; it synapses in minute ganglia located in the renal plexus
splanchnic, lesser thoracic neurons in the intermediolateral cell column of spinal cord levels T10-T11; the lesser thoracic splanchnic nerve appears to arise by multiple contributions from the sympathetic trunk no named branches aorticorenal ganglion; pain from the kidney and suprarenal gland lesser thoracic splanchnic n. passes through the crus of the respiratory diaphragm; postganglionic processes from the ganglion supply vascular smooth muscle of branches of the renal a. and suprarenal aa.; kidney and suprarenal gland
vagus n. medulla: dorsal motor nucleus (GVE preganglionic parasympathetic); inferior ganglion (GVA); nucleus ambiguus (SVE); superior ganglion (GSA); inferior ganglion(SVA) auricular br., pharyngeal br., superior laryngeal, superior and inferior cervical cardiac brs., recurrent laryngeal n., thoracic cardiac brs., brs. to the pulmonary plexus, brs. to the esophageal plexus, anterior and posterior vagal trunks SVE: intrinsic muscles of the larynx, pharynx (except stylopharyngeus), and palate (except tensor veli palatini); GVE: smooth muscle of the respiratory tree & gut (proximal to the left colic flexure), heart; secretomotor: mucous glands of the larynx, respiratory tree, pharynx and gut; secretomotor to digestive glands GSA: skin of the external auditory meatus; GVA: viscera of head, neck, thorax & abdomen proximal to the left colic flexure; SVA: taste from the epiglottis also known as: CN X, 10th cranial nerve; the vagus n. passes through the jugular foramen to exit the posterior cranial fossa; vagus means "wanderer" in reference to its extensive distribution to the body cavities

Arteries of the Superior and Posterior Mediastina

aorta, ascending left ventricle of the heart left and right coronary aa. heart, entire body ascending aorta is the shortest part of the aorta; it continues as the aortic arch
aorta, descending thoracic continuation of aortic arch posterior intercostal aa. 3-11, subcostal aa., left bronchial aa. (2), esophageal aa. (~3), mediastinal brs., superior phrenic aa. thoracic wall, lungs, posterior mediastinum, body below the respiratory diaphragm descending thoracic aorta passes posterior to the diaphragm (aortic hiatus) at the level of the T12 vertebral body; it is continuous with the abdominal aorta
aortic arch the continuation of the ascending aorta brachiocephalic trunk, left common carotid a., left subclavian a. the entire body except the heart aortic arch continues as the descending thoracic aorta; the fibrous ligamentum arteriosum connects to the inferior surface of the aortic arch and it marks the location of the fetal ductus arteriosus aortic arch continues as the descending thoracic aorta
brachiocephalic trunk aortic arch right common carotid a., right subclavian a. right side of the head and neck; right upper limb and right side of the chest wall there is only one brachiocephalic trunk
bronchial, left descending thoracic aorta right bronchial a. (occasionally) lower trachea, bronchial tree there are usually two left bronchial aa.
carotid, common brachiocephalic trunk (right), aortic arch (left) external carotid a., internal carotid a. most of the head and upper neck common carotid a. bifurcates at the level of the superior border of the thyroid cartilage; the internal carotid a. and the external carotid a. are its terminal brs.; the carotid sinus and carotid body are located at the bifurcation
musculophrenic internal thoracic a. anterior intercostal aa. anterior diaphragm, anterior aspects of intercostal spaces 7-10 or 11 musculophrenic a. supplies muscles that develop in the septum transversum
pericardiacophrenic internal thoracic a. pericardial br., sternal br., mediastinal br. pericardial sac, pleura, diaphragm pericardiacophrenic a. accompanies the phrenic n.
phrenic, superior descending thoracic aorta (2 small brs.) no named branches diaphragm superior phrenic a. anastomoses with the musculophrenic a. and the pericardiacophrenic a.
subclavian brachiocephalic a. (right), aortic arch (left) 1st part: vertebral a., thyrocervical trunk, internal thoracic a.; 2nd part: costocervical trunk; 3rd part: dorsal scapular a. (70%) neck, brain, spinal cord, thyroid gland, larynx, shoulder, chest muscles, upper limb subclavian a. is continuous with the axillary a., the name change occurs at the lateral border of the first rib; anterior scalene muscle passes anterior to the subclavian a., dividing it into 3 parts
thoracic, internal subclavian a. (1st part) pericardiocophrenic a., perforating brs., anterior intercostal aa., mediastinal brs., thymic brs., musculophrenic a., superior epigastric a. mediastinum, anterior thoracic wall, anterior abdominal wall, respiratory diaphragm internal thoracic a. is also known as: internal mammary a.

Veins of the Superior and Posterior Mediastina

VeinTributariesDrains IntoRegion DrainedNotes
azygos v. formed by the union of the ascending lumbar v. and the subcostal v.; tributaries: posterior intercostal vv. 11-2 (right superior intercostal), hemiazygos v., accessory hemiazygos v., esophageal v., right bronchial v. posterior surface of the superior vena cava lateral and posterior walls of the abdomen and chest; esophagus; bronchial tree may connect with the inferior vena cava; arch of azygos passes superior to the root of the lung
brachiocephalic v. formed by the union of the subclavian v. and the internal jugular v.; tributaries: vertebral v., thymic v., inferior thyroid v., internal thoracic v., 1st posterior intercostal v., left superior intercostal v. (to the left brachiocephalic v.) the left and right brachiocephalic vv. unite to form the superior vena cava head; neck; upper limb; anterior chest wall at its origin, the left brachiocephalic v. receives the thoracic duct; at its origin, the right brachiocephalic v. receives the right lymphatic duct
esophageal v. tributaries are unnamed azygos v.; hemiazygos v. esophagus esophageal vv. connect with the esophageal brs. of the left gastric, forming a potential portal-caval venous anastomosis (esophageal varices when enlarged)
hemiazygos v. formed by the joining of the left ascending lumbar v. and the left subcostal v.; tributaries: left posterior intercostal vv. 8 or 9-11; esophageal vv. azygos v. inferior levels of the left posterolateral chest wall the azygos system is variable, and levels drained by the hemiazygos v. may vary
hemiazygos, accessory left posterior intercostal vv. 4-7 or 8, left bronchial vv., esophageal vv. azygos v. mid levels of the left posterolateral chest wall the azygos system is variable, and levels drained by the accessory hemiazygos v. may vary
vena cava, inferior formed by the union of the paired common iliac vv; tributaries: lumbar vv. 1-4, right ovarian/testicular v., renal vv., right suprarenal v., right inferior phrenic v., hepatic vv. right atrium all of the body below the level of the respiratory diaphragm the inferior vena cava is longer than the abdominal aorta
vena cava, superior formed by the union of the paired brachiocephalic vv.; tributary: azygos arch right atrium all of the body above the level of the diaphragm except for those regions drained by the pulmonary vv. and coronary vv. superior vena cava is formed posterior to the first costal cartilage on the right side

Lymphatics of the Thorax

Structure Location Afferents from Efferents to Regions drained Notes
bronchomediastinal trunk along the course of the brachiocephalic v. union of efferents from the paratracheal nodes, parasternal nodes and anterior mediastinal nodes left: thoracic duct; right: right lymphatic duct thoracic wall and viscera; medial part of the mammary gland right bronchomediastinal trunk receives lymph from the lower lobe of the left lung; bronchomediastinal trunk may drain directly into the venous system on either side
bronchopulmonary nodes hilum of the lung pulmonary nodes tracheobronchial nodes lung bronchopulmonary nodes are also known as: hilar nodes
cisterna chyli between the abdominal aorta and the inferior vena cava anterior to the body of the L1 or L2 vertebra right and & left lumbar trunks; possibly the intestinal trunk thoracic duct all of the body below the respiratory diaphragm; all of the abdominal and pelvic viscera cisterna chyli is an enlargement of the lower end of the thoracic duct; it occurs in about 25% of individuals
mediastinal nodes, anterior along the course of the brachiocephalic vessels and aorta lymphatic vessels from the anterior mediastinum and middle mediastinum bronchomediastinal trunk thymus, anterior respiratory diaphragm, pericardium, part of the heart anterior mediastinal nodes are from 2 to 5 in number
mediastinal nodes, posterior along azygos system of veins and esophagus viscera of the posterior mediastinum and chest wall thoracic duct, inferior tracheobronchial nodes, superior tracheobronchial nodes posterior mediastinum, posterior aspect of the heart and pericardium, posterior part of the respiratory diaphragm posterior mediastinal nodes drain primarily to the thoracic duct
parasternal nodes lateral border of sternum, along the course of the internal thoracic vessels anterior phrenic nodes, lymphatic vessels from the anterior thoracic wall larger lymphatic vessels in the root of the neck medial side of the mammary gland; medial part of the anterior chest wall and muscles parasternal nodes constitute an important drainage pattern in cases of cancer of the mammary gland; one or two parasternal nodes may be found in the anterior end of intercostal spaces 1-6; also known as: sternal nodes
paratracheal nodes coursing along the lateral surface of the trachea and esophagus superior tracheobronchial nodes bronchomediastinal trunk lungs, trachea, upper esophagus, the part of the larynx below the vocal folds paratracheal nodes are an important group of nodes in cases of pulmonary infection or lung cancer; also known as: tracheal nodes
pulmonary nodes within the lung parenchyma lymphatic vessels from the parenchyma of the lung bronchopulmonary (hilar) nodes lung parenchyma, bronchial tree within the lungs pulmonary nodes are located along the larger bronchi of the lung
thoracic duct between the esophagus anteriorly and the thoracic vertebral bodies posteriorly formed by the union of the lumbar lymph trunks, sometimes dilated to form a cisterna chyli junction of the left subclavian v. and the left internal jugular v. all of the body and limbs below the respiratory diaphragm; the left side of the chest, left upper limb and the left side of the head and neck above the diaphragm thoracic duct is the largest lymphatic vessel; it passes through the aortic hiatus on the right side of aorta; it swings to the left side of the esophagus at the T4-T5 intervertebral disc (at the level of the sternal angle)
tracheobronchial nodes, inferior inferior to tracheal bifurcation bronchopulmonary nodes, left side inferior tracheobronchial nodes drain into right inferior tracheobronchial nodes right superior tracheobronchial nodes lower lobes of the lungs; middle mediastinum; posterior mediastinum left inferior tracheobronchial nodes drain to the right side
tracheobronchial nodes, superior superolateral to the tracheal bifurcation bronchopulmonary (hilar) nodes paratracheal (tracheal) nodes lungs, middle mediastinum, posterior mediastinum inferior tracheobronchial nodes drain lymph from the lower lobe of the left lung to the right superior tracheobronchial nodes

Viscera of the Superior and Posterior Mediastina

Organ/Part of Organ Location/Description Notes
carina keel-shaped cartilage lying within the tracheal bifurcation carina trachealis is an important landmark during endoscopy of the bronchial tree
esophagus the portion of the gastrointestinal tract between the pharynx and the stomach connects: superiorly with laryngopharynx at lower border of cricoid cartilage; inferiorly it passes through diaphragm at the T10 vertebral level to reach the stomach; the upper 1/3 is skeletal muscle innervated by the recurrent laryngeal, the lower 2/3rds is smooth muscle innervated by the vagus nn. via the esophageal plexus
heart muscular pump for blood located within middle mediastinum of the thorax heart is nearly surrounded by the pericardial sac and pericardial cavity
trachea main airway that lies anterior to the esophagus trachea extends from vertebral level C6 to the level of the T4/5 intervertebral disc; superiorly it is connected to the cricoid cartilage via the cricotracheal ligament; it bifurcates into two primary bronchi

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Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of tables edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2005, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.

Unauthorized use is prohibited.