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HSF - Anatomy Mediastinum

Anatomy Exam 2
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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