HSF - Anatomy Mediastinum

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Anatomy Exam 2

divisions of mediastinum

superior (above IV disc between T4 and T5)
inferior (below IV disc between T4 and T5)

superior mediastinum boundaries

a: manubrium sterni
p: T1-T4 vertebrae
L: mediastinal and apical pleura

inferior mediastinum boundaries

A: body of sternum and xiphoid process
P: T5-T12 vertebral bodies
Lateral: Mediastinal pleura
Lower: diaphragm

divisions of inferior mediastinum

anterior, middle, posterior

Contents of superior mediastinum

• thymus
• R & L brachiocephalic veins
• SVC
• Arch of Aorta and branches
- brachiocephalic trunk
- L common carotid artery
- L subclavian artery)
• trachea and bifurcation
• esophagus
• thoracic duct
• R and L phrenic and vagus nerves
• sympathetic chains

Right and Left brachiocephalic veins

formed by union of internal jugular and subclavian vein behind sternoclavicular joint

left brachiocephalic vein runs

obliquiely downards to right and lies immediately behind manurbium sterni

thoracic duct entry into left brachiocephalic vein at

junction between left internal jugular and left subclavian veins

right lymphatic duct drains

into R brachiocephalic vein atformation of the vein

SVC formed by

right and left brachiocephlaic veins

SVC formed behind

right first costal cartilage

SVC opens into

right atrium

SVC opens into RA at

behind right 3rd costal cartilage

Azygos vein drains into

drains into SVC

Arch of Aorta

• in superior mediastinum
• behind lower half of manubrium stern
• forms impression above hilum of left lung
• important for bone marrow biopsy sternal puncture
• seen as aortic knuckle in plain x ray

branches of aorta

Brachiocephalic trunk
L common carotid
L subclavian
arteria thyroidea ima - (may arise from brachiocephalic trunk too)

Ligamentum Arteriosum

remnant of ductus arteriosus; connects Arch of aorta to LEFT PULMONARY artery; left recurrent laryngeal nerve hooks below it

Descending Aorta

in posterior mediastinum
• passes through aortic opening at T12 vertebral level

branches of descending aorta

• posterior intercostal arteries 3-11 intercostal spaces
• subcostal artery
• bronchial arteries
• esophageal arteries
• superior phrenic arteries

path from ascending aorta

brachiocephalic trunk (right carotid, right subclavian); left carotid, left subclavian, descending aorta

Anterior mediastinum contents (2)

thymus gland, sternopericardial ligaments

thymus gland

active lymphatic organ in first 5-6 years in maturation of T lymphocytes, atrophies after puberty and replaced by fat

Superior and Inferior sternopericardial ligaments

fibrous connective tissue connecting body of sternum to pericardium

Middle mediastinum contents:

pericardium, heart and roots of great vessels, right and left bronchi, pulmonary arteries, pulmonary veins, Right and Left phrenic nerves

R and L phrenic nerves roots

from ventral rami of C3-5, pierce diaphragm to supply diaphragm from below

Phrenic nerves area of supply

diaphragm motor (phrenic); sensory (central portion of diaphragm by phrenic and peripheral part by T7-T12 spinal nerves; sensory pericardium, mediastinal pleura, central part of diaphragmatic pleura, peritoneum (abdominal cavity pleura) on diaphragm

diaphragm referred pain to

shoulder

pericardiacophrenic artery origin

as branches of Internal thoracic artery

pericardiacophrenic veins

drain into brachiocephalic vein or internal thoracic vein

Phrenic nerve

runs with pericardiacophrenic vessels

Mediastinal structures

Phrenic Nerves and pericardiacophrenic vessels
• vagus nerves (PS branches to thoracic and some abdominal viscera)
• Ligamentum arteriosum (left recurrent laryngeal nerve hooks below it)

left recurrent laryngeal nerve

hooks below ligamentum arteriosum

right recurrent laryngeal nerve

hooks below right subclavian artery (not seen)

posteior mediastinum contents

• esophagus
• descending thoracic aorta
• R and L vagus nerves
• L recurrent laryngeal
• sympathetic chain and branches
• thoracic duct
• posterior intecostal vessels
• intercostal nerves
• azygos and hemiazygos system of veins
• mediastinal lymph nodes and areaolar tissue

Sympathetic chain and branches

greater, lesser and least splancnic nerves

esophagus

• muscular tube in neck superior and posterior mediastinum
• continuation of pharynx and lower border of cricoid cartilage / C6 vertebra passes through diaphragm at T10 vertebral level
• related to LA
• enlargement of LA from mitral stenosis can be diagnosed by barium swallow

barum swallow

to detect LA enlargement from mitral stenosis

Esophageal Hiatus

T10 vertebra level
• trasnmits esophagus, L and R vagus nerves, esophageal branches of left gastric vessels

hiatal hernia

stomach enters chest through esophageal hiatus, sliding hernia, rolling hernea

constrictions of esophagus

• at beginning opposite C6 Vertebram 6" from incisor teeth
• by arch of aorta opposite T3 Vertbera 9" from incisor teeth
• by left principal bronchus opposite T5 vertebra 11" from incisor teeth
• at esophageal hiatus, opposite T10 vertebra 16" from incisor teeth

Innervation of esophagus

esophageal plexus by branches of sympathetic ganglia and vagus nerves, supply smooth muscles of lower 2/3rd of esophagus

esophageal plexus

formed by L vagus nerve passing in front of esophagus and R vagus nerve passing behind esophagus

R and L vagus nerves thru esoph hiatus

enter abdomen and supply abdominal viscera

Thoracic Duct area of drainage

• lower limbs
• abdomen and pelvis
• left upper limb (let subclaian trunk)
• left side of head and neck ( left jugular trunk)
• left side of chest cavity (left bronchomediastinal trunk)

Thoracic Duct

lymphatic channel with multiple valves giving it beaded appearance

contents of thoracic duct

lymph is milky full of chylomicrons (fat) from intestines

Beginnning of thoracic duct

cisterna chyli

path of thoracic duct

begins at cisterna chili, enters posterior mediastium behind esophagus through aortic opening at T12 vertebral level, passes through superior mediastinum and into neck, opens to let brachiocephalic vein at jan of let internal jugular vein and left subclavian vein

chylothorax

laceration of thoracic duct

Right lymphatic duct area of drainage

right subclavian trunk from upper limb
• right jugular trunk from right side of head and neck
• right bronchomediastinal trunk from right side of chest cavity

drainage of right lymphatic duct

right brachiocephalic vein at jan between right internal jugular vein and right subclavian vein

Aortic opening at

T12, arota thoracic duct and azygos vein

Posterior Intercostal veins

first posterior intercostals drain into brachiocephalic vein directly

superior intercostal vein

formed by 2,3,4 posterior intercostal veins, drains into brachiocephalic vein on left, azygos on right

azygos vein

right 5-11 posterior intecostal veins and subcostal vein drain into azygos vein, also hemiazygos vein and accessory hemiazygos vein. Azygos vein itself drains into SVC.

hemiazygos vein

receives blood from lower left 3-4 (9-11) posterior intercostal veins and subcostal vein

accessory hemiazygos vein

Left 5-6-7-8 posterior intercostal veins drain into it

Azygos vein

connects SVC and IVC, formed by subcostal vein with ascending lumbar vein

azygos vein path

passes through aortic opening in diaphragm, ascends up posterior mediastinu and drains into SVC

Veins draining into azygos vein

hemiazygos, accessory hemiazygos vein, formed by joining of subcostal vein with ascending lumbar vein, right superior intercostal, right 4-11 posterior intercostal veins

Thrombosis of SVC and IVC

azygos, hemiazygos, and accessory hemiazygos veins become engorged and form alternate routes of drainage

Sympathetic chain

contains 12 thoracic sympathetic ganglia made of postganglionic sympathetic neurons

Communicantes

white rami (preganglionic sympathetic) and grey rami (postganglionic sympathetic that connect with spinal nerves from sympathetic chain

postganglionic sympathetic branches to

cardiac plexus, pulmonary plexus and esophageal plexus

preganglionic branches

greater, lesser and least splanchnic nerves pass through diaphragm to supply abdominal viscera

greater splanchnic nerve

preganglionic sympathetic nerve rivers from T5-9 sympathetic ganglia

lesser splanchnic nerve

preganglionic sympathetic fibers from T10-11 sympathetic ganglia

Least splanchnic nerve

preganglionic sympathetic fibers from T12 sympathetic ganglion

Thoracoabdominal diaphragm openins

cavil opening, esophageal opening, aortic opening,

2 parts of diaphragm

muscular and central tendon

aortic opening of diaphragm

T12
• aorta
• thoracic duct
• azygos vein

esophageal opening of diaphragm

T10
• esophagus
• R & L vagus nerves
• branches of left gastric vessels

cavil opening of diaphragm

T8
• inferior vena cava
• branches of right phrenic nerve

motor nerve supply of diaphragm

phrenic

sensory nerve supply of central diaphragm

phrenic

sensory nerve supply of peripheral diaphragm

ventral rami of lower 6 Thoracic nerves

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