Learning Objectives
? Identify the divisions of the mediastinum and describe
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their contents.? Describe the gross anatomy of structures in
mediastinum.
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? Describe the anatomy of nerves in the mediastinum.
? Correlate this knowledge to clinical conditions.
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Boundaries of mediastinumThoracic inlet
Sternal Angle
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sternum
Thoracic vertebra
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Thoracic ouletTS: Mediastinum
CS: Mediastinum
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Mediastinum? Bulky septum
between the
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pleural cavities
& lungs
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Extends-? Root of the
neck to
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diaphragm
? From the
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sternum tovertebral
column
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Divisions of mediastinum? Divided by an imaginary horizontal plane from
the sternal angle to the intervertebral disc
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between 4th & 5th vertebra in to
? superior mediastinum
? Inferior mediastinum ?
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Anterior Middle Posterior
DIVISIONS OF MEDIASTINUM
Boundaries Of Superior Mediastinum
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BOUNDARIES:
? Anterior: manubrium sterni
? Posterior: Upper 4 thoracic vertebrae
? Superior: Plane of thoracic inlet
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? Inferior: Horizontal plane? On each side: Pleura
Superior mediastinum
SUPERIOR MEDIASTINUM
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SUPERIOR MEDIASTINUM
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LEFT
RIGHT
Superior mediastinum
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? Posterior to the sternum & anterior to the
bodies of first four thoracic vertebra
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Superior mediastinumCONTENTS:
? FROM BEHIND FORWARD:
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1.Esophagus
2.Trachea
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3.Arch of aorta & its 3 branches: brachiocephalic,left common carotid & left subclavian arteries
4.Right & left brachiocephalic veins & superior vena
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cava
5.Thymus gland
Other Contents of superior mediastinum
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Nerves:
1. Right & left vagus
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2. Right & left phrenic3. Right & left
sympathetic trunks
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4. Left recurrent
laryngeal
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Lymphatic structures:1. Thoracic duct
2. Lymph nodes
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Thymus
? Asymmetric bilobed gland
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? Upper extent may reach as high as thyroidgland
? Involved in early development of immune
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system
? Large in children
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? Atrophies after pubertyBrachiocephalic veins
?Located immediately
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posterior to thymus?Formed at the jn. of IJ
& subclavian veins.
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? Begins post to clavicle
?Tributaries: vertebral,
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first post. Intercostal,int. thoracic, inf.
Thyroid, thymic veins
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Left superior intercostal vein
? Drains upper two
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or threeintercostal veins,
left bronchial
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veins & left
pericardiophrenic
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veins? Drains in to left
brachiocephalic
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veins
Superior vena cava
? Vertically oriented
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? Begins posteriorto the lower edge
of first costal
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cartilage
? terminates at the
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lower border ofright third costal
cartilage
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Arch of aorta & it's branches
? Begins when
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ascending aortaemerges from
pericardial sac
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? Terminates on left side
of vertebral level
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between Th 4th - 5thBranches-
Brachiocephalic trunk
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Left CCA
Left subclavian
Thyroid ima
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Trachea? Midline structure
? Present anterior to
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esophagus? Swallowing, breathing,
disease & specialized
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instrumentation causes
shift of trachea
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? divides just inferior tosternal angle (T3- T4)
into Right & Left principal
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bronchus
Vagus nerve
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Right Vagus? lies between right
brachiocephalic
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vein & trunk? Descends
posteriorly to the
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root of Right lung
to reach
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esophagus? Gives branches to
esophagus,
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cardiac plexus &
pulmonary plexus
Left Vagus nerve
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? Lies between Lt CCA &
Lt subclavian artery
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? Pass posterior to theroot of lung to reach the
esophagus
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? Gives branches to
esophagus, cardiac &
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pulmonary plexus? Also gives Lt recurrent
laryngeal nerve- arise at
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inferior margin of arch of
aorta, winds around the
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aorta & reaches thegroove between
esophagus & trachea
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Left recurrent laryngeal nerve
? arise at inferior
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margin of arch ofaorta, winds around
the aorta & reaches
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the groove between
esophagus &
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tracheaPhrenic nerve
? Right Phrenic ?enters
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lateral to Right Vagus& beginning of Right
brachiocephalic vein
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? continues inferiorly on
the Right side of sup
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vena cava, onentering middle
mediastinum
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descends along the
Rt side of pericardial
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sac anterior to the Rtlung root
? leaves the thorax with
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inferior vena cava
Left phrenic nerve
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? enters similar toRight Phrenic nerve
? Lateral to Vagus & Lt
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brachiocephalic vein
? Descends on left
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lateral surface ofarch of aorta
? Passes superficial to
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Lt vagus & superior
intercostal vein
Left phrenic nerve
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? In middle
mediastinum lies on
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the Lt side ofpericardial sac
anterior to root of Lt
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lung
? Pierces the
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diaphragm near theapex of the heart
Thoracic duct
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? Major lymphatic vessel
of the body
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? Enters sup.mediastinum from
below at the level of
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T4/5
? continues through the
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superior med. posteriorto arch of aorta
between the esophagus
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& Lt pleura
Anterior Mediastinum
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Lies ant. to pericardium
Boundaries:
Anterior: body of sternum
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Posterior: pericardium
superior: imaginary line
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separating sup. &inf.mediastinum
Infreior: diaphragm
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Lateral: mediastinal pleura
Anterior mediastinum
Thymus
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contains:
Lymph nodes
fat
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Thymus
Located in anterior
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mediastinum.Develops from endoderm
of 3rd pharyngeal pouch
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Present in childhood,involutes in adults
Blood supply
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Arterial :i nt. Mammary arteriesVenous: internal thoracic veins
Lymphatic drainage: lower
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cervical, int. Mammary and hilar
nodes
Esophagus
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? Starts at the C6th &
terminates at cardiac
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opening of stomach(T12)
? Descends anterior to
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vertebral bodies in
midline
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? Crossed laterally by theazygos vein on the right
side & arch of aorta on
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the left side
Posterior Mediastinum
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BOUNDARIES:? Anterior: Pericardium & diaphragm
? Posterior: Lower 8 thoracic vertebrae
? Superior: Horizontal plane
? Inferior: Diaphragm
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? On each side: PleuraPosterior Mediastinum
? CONTENTS:
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1. Esophagus (most anterior structure)2. Thoracic duct
3. Right & left vagus
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4. Descending aorta
5. Azygos & hemiazygos veins
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6. Right & left sympathetic trunks & theirbranches (splanchnic nerves)
7. Lymph nodes
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POSTERIOR MEDIASTINUM
POSTERIOR MEDIASTINUM
POSTERIOR MEDIASTINUM
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POSTERIOR MEDIASTINUMPOSTERIOR MEDIASTINUM
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MIDDLE MEDIASTINUM? CONTENTS:
1. Pericardium & heart
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2. Arteries: ascending aorta, pulmonary trunk
3. Veins: lower half of superior vena cava,
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terminations of inferior vena cava & pulmonaryveins
4. Nerves: phrenic
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5. Lymph nodes
Mediastinum
VEINS
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BRACHIOCEPHALIC: (Superior mediastinum)
? FORMATION: by union of internal jugular & subclavian vein
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(behind medial end of clavicle)? END: Both veins unite to form S.V.C.
? RIGHT VEIN: shorter & has a vertical course, related lateral y to
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right phrenic nerve & right pleura & lung, its tributaries in thorax:
right 1st posterior intercostal vein, right internal thoracic vein,
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right lymphatic duct? LEFT VEIN: longer & has an oblique course, related anteriorly to
manubrium & thymus gland, & posteriorly to branches of arch of
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aorta, its tributaries in thorax: left 1st posterior intercostal vein,
left superior intercostal vein, left internal thoracic vein, thoracic
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ductVEINS
SUPERIOR VENA CAVA: (Superior & middle mediastinum)
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? FORMATION: by union of brachiocephalic veins, behind lower border of
right 1st costal cartilage
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? END: opens into right atrium behind right 3rd costal cartilage? TRIBUTARIES: azygos vein
AZYGOS & HEMIAZYGOS VEINS
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VEINS
AZYGOS VEIN: (Posterior mediastinum)
?
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ORIGIN: by union of right ascending lumbar & subcostal veins
(passes through aortic opening of diaphragm)
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?END: forms an arch above the root of right lung & ends in S.V.C.
opposite lower border of T4
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?
RELATIONS:
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1. Anterior: esophagus2. Posterior: thoracic vertebra
3. Right: right pleura & lung
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4. Left: thoracic duct
?
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TRIBUTARIES: superior & inferior hemiazygos veins, rightsuperior intercostal vein, right posterior intercostal veins (from
4th to 11th), right bronchial veins, esophageal & pericardial veins
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VEINSINFERIOR HEMIAZYGOS: (Posterior
mediastinum)
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?ORIGIN: by union of left ascending lumbar
& subcostal veins (passes through left crus
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of diaphragm)?END: into azygos vein, opposite T8
?TRIBUTARIES: left posterior intercostal
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veins (9th to 11th), esophageal veins
VEINS
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SUPERIOR HEMIAZYGOS: (Posterior mediastinum)? ORIGIN: by left posterior intercostal veins (4th to 8th)
? END: into azygos vein, opposite T7
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? TRIBUTARIES: left bronchial veins
INFERIOR VENA CAVA: (Posterior mediastinum)
? END: passes through vena caval opening of diaphragm
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& opens into right atrium behind right 6th costal
cartilage
Ar
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A teORT rAi:
?
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ASCEND e
IN s
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G AORTA: (Middle mediastinum)1. ORIGIN: at the base of left ventricle opposite lower border of left 3rd
costal cartilage
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2. END: ascends upward, forward & to the right & continues as arch of
aorta
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3. BRANCHES: right & left coronary arteriesAr
? te
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ARrCieH sOF AORTA: (Superior mediastinum)1. ORIGIN: continuation of ascending aorta, opposite upper border of
right 2nd costal cartilage
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2. COURSE & RELATIONS: ascends upward backward & to the left
(behind manubrium & in front of trachea) then curves backward (to
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the left of trachea) then final y curves downward3. TERMINATION: continues as descending aorta, opposite lower border
of T4
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Ar?
teBRArNiCHeESs OF ARCH OF AORTA: (Superior mediastinum)
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1. BRACHIOCEPHALIC: ascends upward & to the right (behindleft brachiocephalic vein & in front of trachea) & divides
into right common carotid & right subclavian arteries
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(behind right sternoclavicular joint)
2. LEFT COMMON CAROTID: ascends upward & to the left (to
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the left side of brachiocephalic artery) & enters the neck(behind left sternoclavicular joint)
3. LEFT SUBCLAVIAN: ascends upward (behind left common
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carotid artery, in front of esophagus, to the left side of
trachea), arches over apex of left lung to enter neck
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ArDES te
CENDI rNie
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G AO sRTA: (Posterior mediastinum)?
ORIGIN: continuation of arch of aorta
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?
TERMINATION: passes through aortic opening of
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diaphragm (opposite T12) & continues as abdominal aorta?
RELATIONS:
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1. Anterior: esophagus
2. Posterior: thoracic vertebrae
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3. Right: thoracic duct4. Left: left pleura & lung
?
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BRANCHES: posterior intercostal (from 3rd to 11th),
subcostal, bronchial, esophageal, pericardial arteries
Ar
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PUL teMON rARiYe TRsUNK (Middle mediastinum)
? ORIGIN: from upper part of right ventricle, behind
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sternal end of left 3rd costal cartilage
? COURSE: ascends upward & to the left & divides (at
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lower border of T4) into:1. Right pulmonary: runs behind ascending aorta &
S.V.C to enter root of right lung
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2. Left pulmonary: runs in front of desending aorta to
enter root of left lung
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T? RAC
BEGIN H
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NIN EAG: continuation of larynx, opposite C6
? TERMINATION: bifurcates into 2 bronchi, opposite lower border
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of T4
? RELATIONS: (in superior mediastinum)
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1. Anterior: arch of aorta, brachiocephalic & left common carotidarteries
2. Posterior: left recurrent laryngeal nerve, esophagus
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3. Right: right vagus nerve
4. Left: arch of aorta, left subclavian artery
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? NERVE SUPPLY: sympathetic trunks & vagus? BLOOD SUPPLY: inferior thyroid vessels
? LYMPHATIC DRAINAGE: pretracheal & paratracheal
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ESOP? BEGINNI H
NG: AG
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contin UuatiSon of pharynx, opposite C6? TERMINATION: passes through esophageal opening of diaphragm
(opposite T10) & joins stomach
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? RELATIONS: (in superior mediastinum)
1. Anterior: left recurrent laryngeal nerve, trachea, left subclavian artery
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2. Posterior: thoracic vertebrae3. Right: right pleura & lung
4. Left: thoracic duct, left pleura & lung
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ESOP?RELATIHONAGS: (inU pSosterior mediastinum)
1.Anterior: pericardium, separating it from left atrium
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2.Posterior: thoracic duct, descending aorta, azygos vein3.Right: right pleura & lung
4.Left: descending aorta, left pleura & lung
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? NERVE SUPPLY: as trachea
? ARTERIAL SUPPLY: descending aorta
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? VENOUS DRAINAGE: azygos & hemiazygos? LYMPHATIC DRAINAGE: posterior mediastinal lymph
nodes
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THORACIC DUCT? ORIGIN: from upper end of cysterna chyli (opposite
L1 & L2)
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? COURSE: passes through aortic opening ofdiaphragm, ascends in posterior mediastinum
(behind esophagus) & in superior mediastinum (to
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the left of esophagus) to enter root of neck
? END: in left brachiocephalic vein
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? RELATIONS: ( in posterior mediastinum)1. Anterior: esophagus
2. Posterior: thoracic vertebrae
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3. Right: azygos vein
4. Left: descending aorta
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THORACIC DUCTTRIBUTARIES:
? It drains lymph from both sides of the body below
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the diaphragm through cysterna chyli
? It drains lymph from left half of the body above
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diaphragm through:1. Left jugular lymph trunk: drains left side of head &
neck
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2. Left subclavian lymph trunk: drains left upper limb
3. Left bronchomediastinal lymph trunk: drains left
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side of thoraxRIGHT LYMPHATIC DUCT
? ORIGIN: formed by union of:
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1. Right jugular lymph trunk: drains rightside of head & neck
2. Right subclavian lymph trunk: drains
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right upper limb
3. Right bronchomediastinal lymph trunk:
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drains right side of thorax? END: in right brachiocephalic vein
NERVES
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PHRENIC NERVES: (Superior & middle mediastinum)?
ORIGIN: anterior rami of C3,4,5
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?
COURSE & RELATIONS IN THORAX:
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1. RIGHT: descends to the right side of: right brachiocephalic vein,S.V.C., pericardium, I.V.C.
2. LEFT: descends to the left side of: arch aorta, pericardium
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?
BRANCHES:
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1. Motor branches to: diaphragm2. Sensory branches from:
?
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Mediastinal & central part of diaphragmatic pleura
?
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Fibrous pericardium & parietal layer of serous pericardium?
Peritoneum covering central part of undersurface of diaphragm
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NERVES? VAGUS NERVES: (Superior & posterior mediastinum)
? ORIGIN: 10th cranial nerve
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? COURSE & RELATIONS IN THORAX:1. RIGHT: descends to the right side of: trachea, behind
root of right lung (pulmonary plexus), behind
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esophagus (esophageal plexus), passes through
esophageal opening of diaphragm to reach posterior
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surface of stomach2. LEFT: descends to the left side of: arch aorta, behind
root of left lung (pulmonary plexus), in front of
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esophagus (esophageal plexus), passes through
esophageal opening of diaphragm to reach anterior
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surface of stomachNERVES
BRANCHES IN THORAX:
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? BOTH VAGI: to lungs & esophagus
? RIGHT VAGUS: to heart
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? LEFT VAGUS: left recurrent laryngeal nerve:curves below arch of aorta, behind ligamentum
arteriosum, ascends in groove between trachea
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& esophagus to reach the neck. It supplies: heart,
trachea, esophagus (in thorax) & larynx (in neck)
NERVES
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THORACIC PART OF SYMPATHETIC TRUNKS: (Superior &posterior mediastinum)
? BEGINNING: the cervical part continues as thoracic
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part by passing in front of neck of first rib
? TERMINATION: the thoracic part continues as lumbar
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part by passing behind medial arcuate ligament? COURSE:
1. In upper part of thorax: descend in front of heads of
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ribs
2. In lower part of thorax: descend on the sides of
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bodies of vertebrae? GANGLIA: usual y 11 (1st thoracic ganglion fuses with
inferior cervical ganglion forming stel ate ganglion)
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NERVES
?
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BRANCHES:1. Rami communicantes: each ganglion receives a
white ramus (preganglionic) & gives a grey ramus
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(postganglionic) to corresponding thoracic spinal
nerve
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2. Visceral branches (postganglionic) to thoracic organs(from upper 5 ganglia): to heart, lungs, esophagus,
descending aorta
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3. Visceral branches (preganglionic) to abdominal
organs:
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? Greater splanchnic nerve (from 5th to 9th ganglia)? Lesser splanchnic nerve (from 10th 7 11th ganglia)
? Lowest splanchnic nerve (from 12th ganglion)
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Nerves in mediastinum
? The right vagus nerve descends in
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the thorax, first posterolateral to the
brachiocephalic artery then lateral
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to the trachea? Passes behind the root of the right
lung and assists in the formation of
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the pulmonary plexus.
? On leaving the plexus, the vagus
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passes onto the posterior surface ofthe esophagus and takes part in the
formation of the esophageal
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plexus.
? It then passes through the
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esophageal opening of thediaphragm.
Nerves in mediastinum
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? The left vagus nerve descends inthe thorax between the left
common carotid and the left
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subclavian arteries
? It then crosses the left side of the
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aortic arch? The vagus then turns backward
behind the root of the left lung and
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assists in the formation of the
pulmonary plexus.
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? On leaving the plexus, the vaguspasses onto the anterior surface of
the esophagus and takes part in
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the formation of the esophageal
plexus.
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Nerves in mediastinum
? The right phrenic nerve
descends in the thorax along the
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right side of the right
brachiocephalic vein and the
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superior vena cava .? It passes in front of the root of
the right lung and runs along the
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right side of the pericardium, which
separates the nerve from the right
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atrium.? It then descends on the right side
of the inferior vena cava to t`he
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diaphragm.
? Its terminal branches pass through
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the caval opening in thediaphragm to supply the central
part of the peritoneum on its under
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aspect.
Nerves in mediastinum
? The left phrenic nerve descends
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in the thorax along the left side of
the left subclavian artery.
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? It crosses the left side of the aorticarch and here crosses the left side
of the left vagus nerve.
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? It passes in front of the root of the
left lung and then descends over
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the left surface of the pericardium,which separates the nerve from
the left ventricle.
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? On reaching the diaphragm, the
terminal branches pierce the
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muscle and supply the central partof the peritoneum on its under
aspect.
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anatomical
Acc. To felson
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Clinical correlations? Deflection of Mediastinum
?If air enters the pleural
cavity (a condition called
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pneumothorax), the lung
on that side immediately
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collapses and themediastinum is displaced to
the opposite side.
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?patient's being breathless
and in a state of shock; on
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examination, the tracheaand the heart are found to
be displaced to the opposite
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side
Clinical correlations
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? Mediastinitis?Deep infection of the neck spread readily into the thorax,
producing a mediastinitis.
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?Penetrating wounds of the chest involving the esophagusmay produce a mediastinitis.
Clinical correlations
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? Mediastinal Tumors or Cysts
?Enlargement of mediastinal tumor
may compress the left recurrent
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laryngeal nerve, producing
paralysis of the left vocal fold.
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?An expanding cyst or tumor canpartially occlude the superior vena
cava, causing severe congestion
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of the veins of the upper part of
the body.
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?Other pressure effects can beseen on the sympathetic trunks,
phrenic nerves, and sometimes
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the trachea, main bronchi, and
esophagus.
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Clinical correlations
? Mediastinoscopy
?diagnostic procedure by which
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tracheobronchial lymph nodes
are obtained without opening the
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pleural cavities.?A small incision is made in the
midline in the neck just above
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the suprasternal notch, and
the superior mediastinum is
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explored down to the region ofthe bifurcation of the trachea.
?The procedure can be used to
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determine the diagnosis and
degree of spread of carcinoma
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of the bronchus.Summary
? Mediastinum: definition
? Extend and sub
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divisions
? Contents
? Nerves passing thorax
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? Clinical correlations