Anatomy Tables - Posterior Mediastinum

Topographic Anatomy

Structure/Space Description/Boundaries Significance
posterior mediastinum (N231,TG4-35,TG4-36,TG4-37) between pericaridal sac and vertebral bodies contains esophagus, descending thoracic aorta, azygos system, thoracic duct, and lymph nodes (Latin, medius = middle + stare = stand, thus that areas which stands in the middle of the thorax)


Muscle Origin Insertion Action Innervation Artery Notes Image
subcostalis (N254,TG4-41) angle of ribs angle of a rib 2-3 ribs above origin compresses the intercostal spaces intercostal nerves intercostal a. subcostalis, transversus thoracis & innermost intercostal mm. make up the deepest intercostal muscle layer (Latin, costa = rib)


Artery Source Branches Supply to Notes
aorta, descending thoracic(N206,N232,TG4-38,TG4-39) 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
bronchial, left (N207,TG4-39) descending thoracic aorta right bronchial (occasionally) lower trachea, bronchial tree usually 2 in number
esophageal (N237,TG4-39) descending thoracic aorta lower 2/3rds of thoracic esophagus there are usually two, although there may be three esophageal brs. of aorta; anastomoses with esophageal brs. of left gastric a.
intercostal, posterior (N172,N192,N237,TG4-39,TG4-10, Practical) supreme/highest intercostal (upper 2 spaces), descending thoracic aorta (3rd-11th spaces) posterior br., spinal br., anterior br., collateral br., lateral cutaneous br. intercostal muscles posteriorly & laterally & overlying muscles, spinal cord & vertebral column & back muscles, skin & superficial fascia posteriorly & laterally (Latin, costa = rib)
subcostal (N264,TG4-39) descending thoracic aorta spinal br., collateral br., lateral cutaneous br. vertebra & spinal cord; muscles, skin & fascia of upper abdominal wall (Latin, costa = rib)


Vein Tributaries Drains Into Region Drained Notes
azygos (N238,TG4-40, Practical) union of ascending lumbar & subcostal; post. intercostals 11-2 (rt. sup. intercostal), hemiazygos, accessory hemiazygos, esophageal, rt. bronchial sup. vena cava lateral & post. abdominal/chest wall, esophagus, bronchial tree may connect with inf. vena cava; arch of azygos passes sup. to root of lung (Greek,a- = not + zygon = yoke, therefore unyoked or unpaired, as the azygos vein)
hemiazygos (N238,TG4-40) formed by union of left ascending lumbar & subcostal vv.; tributaries: left posterior intercostal vv. 11-9 or 8, esophageal vv. azygos v. lower posterolateral chest wall on left side levels drained may vary
hemiazygos, accessory (N238,TG4-40) left posterior intercostal vv. 5-7 or 8, left bronchial vv., esophageal vv. azygos v. middle posterolateral chest wall on left side levels drained may vary
brachiocephalic (N206,N212,N238,TG4-19,TG4-18) union of subclavian & internal jugular; vertebral, thymic, inferior thyroid, internal thoracic, 1st post. intercostal, left sup. intercostal (to left brachiocephalic) left & right brachiocephalic unite to form sup. vena cava head, neck, upper limb, anterior chest wall at its origin, left brachiocephalic receives thoracic duct, right receives right lymphatic duct
intercostal, posterior (N231,TG4-40) spinal trib., posterior trib., collateral trib., lateral cutaneous trib. 1st: brachiocephalic; 2nd-4th: superior intercostal; right 5th-11th: azygos; left 5th-7th or 8th: accessory hemiazygos; left 9th-11th: hemiazygos intercostal space & muscles & adjacent ribs, spinal cord segment & vertebra
intercostal, superior (N230,TG4-40), Practical1, Practical2, Practical3, Practical4) 2nd-4th posterior intercostal right: arch of azygos; left: left brachiocephalic intercostal spaces 2-4
thoracic, internal (TG4-17) union of musculophrenic and superior epigastric; ant. intercostal, perforating right - superior vena cava; left - left brachiocephalic anterior chest wall and upper anterior abdominal wall
thymic (N211,TG4-19, Practical) left brachiocephalic thymus (or thymic fat in adult)
thyroid, inferior  (N238,TG7-13,TG4-19, Practical) left brachiocephalic thyroid gland inferiorly
vena cava, inferior (Practical) union of paired common iliacs; lumbar vs. 4-1, rt. ovarian/testicular, renal vs., rt. suprarenal, rt. inferior phrenic, hepatic vs. rt. atrium body below diaphragm
vena cava, superior (N206,N212,N238,TG4-19,TG4-15, Practical1, Practical2) union of paired brachiocephalics; azygos arch rt. atrium body above diaphragm except for pulmonary vs. & heart


Structure Location Afferents from Efferents to Regions drained Notes
thoracic duct (N206,N266,TG4-44, Practical1, Practical2) between esophagus & thoracic vertebral bodies union of lumbar lymph trunks, sometimes dilated to form cisterna chyli junction of left internal jugular v. and left brachiocephalic v. body below diaphragm, left side of body above diaphragm largest lymph vessel; passes up through aortic hiatus on right side of aorta, swings to left side of esophagus at T4-T5 disc


Nerve Source Branches Motor Sensory Notes
phrenic n. (TG4-20,TG4-29, Practical1, Practical2, Practical3) 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. (Greek, phren = diaphragm, for which we derive the word "frenzy," for the diaphragm was considered to be the seat of emotions)
vagus n. (TG7-51,TG7-52, Practical1, Practical2) 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; (Latin, vagus = wanderer, so called because of its wide distribution to the body cavities)
esophageal plexus (N209,N240,TG4-38,TG4-45, Practical) right & left vagus nn.; thoracic visceral brs. of sympathetic trunk anterior & posterior vagal trunks parasympathetic from vagus supplies smooth muscle & glands of thoracic esophagus & abdominal gut proximal to splenic flexure; sympathetics from thoracic visceral brs. supply vascular smooth muscle in esophageal vessels vagus: GVA from esophagus & abdominal gut proximal to splenic flexure; thoracic visceral brs.: pain from esophagus (Latin, plexus = a braid)
sympathetic chain ganglia (N209,N240,N258,N192,TG4-45,TG4-46) pregang. symp. via white rami communicans of VPR of T1-L2 postgang. symp. via gray rami communicans to all spinal ns.; internal & external carotid ns.; cervical cardiac brs.; thoracic visceral brs.; greater, lesser & least thoracic splanchnic ns.; lumbar splanchnic ns.; sacral splanchnic ns. dilator pupillae, vascular smooth muscle, arrector pili muscles, sweat glands, adrenal medulla, heart, lungs & gut (moderate muscle contractions, not initiate) pain from viscera located parallel & lateral to vertebral bodies in neck, thorax & abdominopelvic cavity (Greek, ganglion = a swelling or knot)
stellate ganglion (N209,N240,TG4-45,TG4-46, Practical1, Practical2) pregang. symp. via white rami communicans of T1 postgang. symp. via gray rami communicans to C8& T1; thoracic visceral br. vascular smooth muscle, arrector pili muscle, sweat glands of C8 & T1 cutaneous distribution on chest & upper limb; vascular smooth muscle of lungs pain from lungs stellate is the frequent fusion of inferior cervical ganglion & T1 ganglion of sympathetic trunk (Latin, stella = star + ganglion = a swelling or knot)
splanchnic, thoracic (TG4-46, Practical1, Practical2, Practical3, Practical4) neurons in intermediolateral cell column of spinal levels T5-T12; nerves appear to arise by multiple contributions from sympathetic trunk greater thoracic splanchnic (formed by union of brs. emerging from ganglia T5-T9); lesser thoracic splanchnic (formed by union of brs. emerging from ganglia T10-T11); least thoracic splanchnic (formed by union of brs. emerging from ganglion T12) to pre-aortic or prevertebral ganglia in abdomen; postganglionic processes from prevertebral ganglia supply smooth muscles of vessels and adrenal medulla which releases epinephrine and norepinephrine pain from abdominal viscera pass through crura of diaphragm; greater thoracic splanchnic synapses in celiac & superior mesenteric ganglia; lesser thoracic splanchnic synapses in aorticorenal ganglion; least thoracic splanchnic synapses in renal plexus (Greek, splanchonon = viscera)


Organ/Part of Organ Location/Description Notes
esophagus (N232,TG4-38, Practical) connects: superiorly with laryngopharynx at lower border of cricoid cartilage; inferiorly it passes through diaphragm at T10 vertebral level to reach stomach upper third is skeletal muscle innervated by recurrent laryngeal, lower 2/3rds is smooth muscle innervated by vagus via esophageal plexus

Clinical Terms

Term Definition
chylothorax accumulation of chyle (lymph from the GI tract) in the thoracic cavity (Greek, cylos = juice + thorax = breastplate)
tracheo-esophageal fistula (upper esophageal atresia) congenital anomaly in which the upper esophagus ends (atresia) and does not connect with the stomach, and the lower esophagus connects to the trachea (tracheoesophageal fistula); a common complication seen shortly after birth is an aspiration pneumonia - infants will demonstrate excessive salivation, gagging, and coughing with feeding, poor feeding and a bluish discoloration of the skin (cyanosis); treatment involves the surgical repair of the esophagus before the child can take anything by mouth
visceral pain pain relating to the viscera (i.e., splanchnic); mediated by the autonomic nervous system
referred pain pain that is felt somewhere other than a region from which it originates; mediated by the autonomic nervous system
carcinoma any of the various types of malignant (invasive) neoplasm derived from epithelial tissue in several sites, occurring more frequently in skin, bronchi, stomach, and prostate gland in men, and in the breast, cervix, and skin in women (Greek, carcino- = cancer + -oma = tumor)
tachycardic patient with a rapid beating of the heart, defined as over 100 beats/minute
edematous swollen due to excessive fluid accumulation in the intercellular tissue space (Greek, oidema/edema = swelling)
radical neck dissection a common major operation performed to remove malignancies of the head and neck; the neck must be opened laterally and the majority of the sternocleidomastoid muscle is removed along with the regional cervical lymph nodes, the jugular vein, accessory nerve, submaxillary and parotid glands
epistaxis nosebleed
murmur a finding that can be indicative of heart disease. Murmurs can result from abnormalities in the heart or vessels that lead to turbulent flow

The material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger
Published by ILOC, Inc., New York
Copyright © 1995, unauthorized use prohibited.
The excellent editorial assistance of
Dr. Pat Tank, UAMS
is gratefully acknowledged.