Download MBBS Anatomy PPT 46 Mediastinum Notes

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 mediastinum

Thoracic inlet

Sternal Angle

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sternum

Thoracic vertebra

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Thoracic oulet

TS: Mediastinum

CS: Mediastinum

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Mediastinum

? Bulky septum

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between the

pleural cavities

& lungs

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Extends-

? Root of the

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neck to

diaphragm

? From the

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sternum to

vertebral

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column
Divisions of mediastinum

? Divided by an imaginary horizontal plane from

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the sternal angle to the intervertebral disc

between 4th & 5th vertebra in to

? superior mediastinum

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? Inferior mediastinum ?

Anterior Middle Posterior

DIVISIONS OF MEDIASTINUM

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Boundaries Of Superior Mediastinum

BOUNDARIES:
? Anterior: manubrium sterni

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? Posterior: Upper 4 thoracic vertebrae
? Superior: Plane of thoracic inlet
? Inferior: Horizontal plane
? On each side: Pleura

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Superior mediastinum

SUPERIOR MEDIASTINUM

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SUPERIOR MEDIASTINUM


LEFT

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RIGHT
Superior mediastinum

? Posterior to the sternum & anterior to the

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bodies of first four thoracic vertebra

Superior mediastinum

CONTENTS:

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? FROM BEHIND FORWARD:

1.Esophagus

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2.Trachea

3.Arch of aorta & its 3 branches: brachiocephalic,

left common carotid & left subclavian arteries

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4.Right & left brachiocephalic veins & superior vena

cava

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5.Thymus gland

Other Contents of superior mediastinum

Nerves:

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1. Right & left vagus

2. Right & left phrenic

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3. Right & left

sympathetic trunks

4. Left recurrent

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laryngeal

Lymphatic structures:

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1. Thoracic duct

2. Lymph nodes

Thymus

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? Asymmetric bilobed gland

? Upper extent may reach as high as thyroid

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gland

? Involved in early development of immune

system

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? Large in children

? Atrophies after puberty
Brachiocephalic veins

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?Located immediately

posterior to thymus

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?Formed at the jn. of IJ

& subclavian veins.

? Begins post to clavicle

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?Tributaries: vertebral,

first post. Intercostal,

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int. thoracic, inf.

Thyroid, thymic veins

Left superior intercostal vein

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? Drains upper two

or three

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intercostal veins,

left bronchial

veins & left

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pericardiophrenic

veins

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? Drains in to left

brachiocephalic

veins

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Superior vena cava

? Vertically oriented
? Begins posterior

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to the lower edge

of first costal

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cartilage

? terminates at the

lower border of

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right third costal

cartilage

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Arch of aorta & it's branches

? Begins when

ascending aorta

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emerges from

pericardial sac

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? Terminates on left side

of vertebral level

between Th 4th - 5th

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Branches-

Brachiocephalic trunk

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Left CCA
Left subclavian

Thyroid ima
Trachea

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? Midline structure
? Present anterior to

esophagus

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? Swallowing, breathing,

disease & specialized

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instrumentation causes

shift of trachea

? divides just inferior to

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sternal angle (T3- T4)

into Right & Left principal

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bronchus

Vagus nerve

Right Vagus

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? lies between right

brachiocephalic

vein & trunk

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? Descends

posteriorly to the

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root of Right lung

to reach

esophagus

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? 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 the

root 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 the

groove between

esophagus & trachea

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Left recurrent laryngeal nerve

? arise at inferior

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margin of arch of

aorta, winds around

the aorta & reaches

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the groove between

esophagus &

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trachea
Phrenic 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, on

entering middle

mediastinum

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descends along the

Rt side of pericardial

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sac anterior to the Rt

lung root

? leaves the thorax with

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inferior vena cava

Left phrenic nerve

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? enters similar to

Right Phrenic nerve

? Lateral to Vagus & Lt

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brachiocephalic vein

? Descends on left

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lateral surface of

arch of aorta

? Passes superficial to

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Lt vagus & superior

intercostal vein

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Left phrenic nerve

? In middle

mediastinum lies on

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the Lt side of

pericardial sac

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anterior to root of Lt

lung

? Pierces the

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diaphragm near the

apex of the heart

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Thoracic duct

? Major lymphatic vessel

of the body

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? Enters sup.

mediastinum from

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below at the level of

T4/5

? continues through the

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superior med. posterior

to arch of aorta

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between the esophagus

& Lt pleura

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Anterior Mediastinum

Lies ant. to pericardium
Boundaries:

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Anterior: body of sternum

Posterior: pericardium

superior: imaginary line

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separating sup. &

inf.mediastinum

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Infreior: diaphragm

Lateral: mediastinal pleura

Anterior mediastinum

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Thymus

contains:

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Lymph nodes
fat

Thymus

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Located in anterior

mediastinum.
Develops from endoderm

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of 3rd pharyngeal pouch

Present in childhood,

involutes in adults

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Blood supply

Arterial :i nt. Mammary arteries

Venous: internal thoracic veins

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Lymphatic drainage: lower

cervical, int. Mammary and hilar

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nodes
Esophagus

? Starts at the C6th &

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terminates at cardiac

opening of stomach

(T12)

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? Descends anterior to

vertebral bodies in

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midline

? Crossed laterally by the

azygos vein on the right

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side & arch of aorta on

the left side

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Posterior Mediastinum

BOUNDARIES:
? Anterior: Pericardium & diaphragm
? Posterior: Lower 8 thoracic vertebrae

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? Superior: Horizontal plane
? Inferior: Diaphragm
? On each side: Pleura

Posterior Mediastinum

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? CONTENTS:

1. Esophagus (most anterior structure)

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2. Thoracic duct

3. Right & left vagus

4. Descending aorta

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5. Azygos & hemiazygos veins

6. Right & left sympathetic trunks & their

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branches (splanchnic nerves)

7. Lymph nodes

POSTERIOR MEDIASTINUM

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POSTERIOR MEDIASTINUM

POSTERIOR MEDIASTINUM

POSTERIOR MEDIASTINUM

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POSTERIOR MEDIASTINUM


MIDDLE MEDIASTINUM

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? CONTENTS:

1. Pericardium & heart

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2. Arteries: ascending aorta, pulmonary trunk

3. Veins: lower half of superior vena cava,

terminations of inferior vena cava & pulmonary

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veins

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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duct

VEINS

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: esophagus

2. 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, right

superior intercostal vein, right posterior intercostal veins (from

4th to 11th), right bronchial veins, esophageal & pericardial veins

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VEINS

INFERIOR HEMIAZYGOS: (Posterior

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mediastinum)

?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

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?TRIBUTARIES: left posterior intercostal

veins (9th to 11th), esophageal veins

VEINS

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SUPERIOR HEMIAZYGOS: (Posterior mediastinum)

? ORIGIN: by left posterior intercostal veins (4th to 8th)

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? END: into azygos vein, opposite T7

? TRIBUTARIES: left bronchial veins
INFERIOR VENA CAVA: (Posterior mediastinum)

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? END: passes through vena caval opening of diaphragm

& opens into right atrium behind right 6th costal

cartilage

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Ar
A te

ORT 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

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costal cartilage

2. END: ascends upward, forward & to the right & continues as arch of

aorta

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3. BRANCHES: right & left coronary arteries

Ar
? te

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ARrCieH sOF AORTA: (Superior mediastinum)

1. ORIGIN: continuation of ascending aorta, opposite upper border of

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right 2nd costal cartilage

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 downward

3. TERMINATION: continues as descending aorta, opposite lower border

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of T4

Ar
?

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teBRArNiCHeESs OF ARCH OF AORTA: (Superior mediastinum)

1. BRACHIOCEPHALIC: ascends upward & to the right (behind

left brachiocephalic vein & in front of trachea) & divides

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into right common carotid & right subclavian arteries

(behind right sternoclavicular joint)

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2. LEFT COMMON CAROTID: ascends upward & to the left (to

the left side of brachiocephalic artery) & enters the neck

(behind left sternoclavicular joint)

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3. LEFT SUBCLAVIAN: ascends upward (behind left common

carotid artery, in front of esophagus, to the left side of

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trachea), arches over apex of left lung to enter neck

Ar
DES te

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CENDI rNie

G AO sRTA: (Posterior mediastinum)

?

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ORIGIN: continuation of arch of aorta

?

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TERMINATION: passes through aortic opening of

diaphragm (opposite T12) & continues as abdominal aorta

?

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RELATIONS:

1. Anterior: esophagus

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2. Posterior: thoracic vertebrae

3. Right: thoracic duct

4. Left: left pleura & lung

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?

BRANCHES: posterior intercostal (from 3rd to 11th),

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subcostal, bronchial, esophageal, pericardial arteries
Ar
PUL te

MON rARiYe TRsUNK (Middle mediastinum)

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? ORIGIN: from upper part of right ventricle, behind

sternal end of left 3rd costal cartilage

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? COURSE: ascends upward & to the left & divides (at

lower border of T4) into:

1. Right pulmonary: runs behind ascending aorta &

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S.V.C to enter root of right lung

2. Left pulmonary: runs in front of desending aorta to

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enter root of left lung

T
? RAC

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BEGIN H

NIN EA

G: continuation of larynx, opposite C6

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? TERMINATION: bifurcates into 2 bronchi, opposite lower border

of T4

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? RELATIONS: (in superior mediastinum)

1. Anterior: arch of aorta, brachiocephalic & left common carotid

arteries

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2. Posterior: left recurrent laryngeal nerve, esophagus

3. Right: right vagus nerve

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4. Left: arch of aorta, left subclavian artery

? NERVE SUPPLY: sympathetic trunks & vagus

? BLOOD SUPPLY: inferior thyroid vessels

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? LYMPHATIC DRAINAGE: pretracheal & paratracheal

ESOP
? BEGINNI H

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NG: AG

contin UuatiSon of pharynx, opposite C6

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? TERMINATION: passes through esophageal opening of diaphragm

(opposite T10) & joins stomach

? RELATIONS: (in superior mediastinum)

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1. Anterior: left recurrent laryngeal nerve, trachea, left subclavian artery

2. Posterior: thoracic vertebrae

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3. Right: right pleura & lung

4. Left: thoracic duct, left pleura & lung

ESOP?RELATIHONAGS: (inU pSosterior mediastinum)

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1.Anterior: pericardium, separating it from left atrium

2.Posterior: thoracic duct, descending aorta, azygos vein

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3.Right: right pleura & lung

4.Left: descending aorta, left pleura & lung

? NERVE SUPPLY: as trachea

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? ARTERIAL SUPPLY: descending aorta

? VENOUS DRAINAGE: azygos & hemiazygos

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? LYMPHATIC DRAINAGE: posterior mediastinal lymph

nodes
THORACIC DUCT
? ORIGIN: from upper end of cysterna chyli (opposite

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L1 & L2)

? COURSE: passes through aortic opening of

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diaphragm, ascends in posterior mediastinum

(behind esophagus) & in superior mediastinum (to

the left of esophagus) to enter root of neck

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? END: in left brachiocephalic vein

? RELATIONS: ( in posterior mediastinum)

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1. Anterior: esophagus

2. Posterior: thoracic vertebrae

3. Right: azygos vein

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4. Left: descending aorta

THORACIC DUCT

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TRIBUTARIES:

? It drains lymph from both sides of the body below

the diaphragm through cysterna chyli

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? It drains lymph from left half of the body above

diaphragm through:

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1. Left jugular lymph trunk: drains left side of head &

neck

2. Left subclavian lymph trunk: drains left upper limb

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3. Left bronchomediastinal lymph trunk: drains left

side of thorax

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RIGHT LYMPHATIC DUCT

? ORIGIN: formed by union of:

1. Right jugular lymph trunk: drains right

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side of head & neck

2. Right subclavian lymph trunk: drains

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right upper limb

3. Right bronchomediastinal lymph trunk:

drains right side of thorax

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? END: in right brachiocephalic vein

NERVES
PHRENIC NERVES: (Superior & middle mediastinum)

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?

ORIGIN: anterior rami of C3,4,5

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?

COURSE & RELATIONS IN THORAX:

1. RIGHT: descends to the right side of: right brachiocephalic vein,

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S.V.C., pericardium, I.V.C.

2. LEFT: descends to the left side of: arch aorta, pericardium

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?

BRANCHES:

1. Motor branches to: diaphragm

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2. Sensory branches from:

?

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Mediastinal & central part of diaphragmatic pleura

?

Fibrous pericardium & parietal layer of serous pericardium

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?

Peritoneum covering central part of undersurface of diaphragm
NERVES

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? VAGUS NERVES: (Superior & posterior mediastinum)

? ORIGIN: 10th cranial nerve

? COURSE & RELATIONS IN THORAX:

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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

surface of stomach

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2. 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

surface of stomach

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NERVES

BRANCHES IN THORAX:

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? BOTH VAGI: to lungs & esophagus

? RIGHT VAGUS: to heart

? LEFT VAGUS: left recurrent laryngeal nerve:

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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

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? The right vagus nerve descends in

the thorax, first posterolateral to the

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brachiocephalic artery then lateral

to the trachea

? Passes behind the root of the right

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lung and assists in the formation of

the pulmonary plexus.

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? On leaving the plexus, the vagus

passes onto the posterior surface of

the esophagus and takes part in the

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formation of the esophageal

plexus.

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? It then passes through the

esophageal opening of the

diaphragm.

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Nerves in mediastinum
? The left vagus nerve descends in

the thorax between the left

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common carotid and the left

subclavian arteries

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? It then crosses the left side of the

aortic arch

? The vagus then turns backward

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behind the root of the left lung and

assists in the formation of the

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pulmonary plexus.

? On leaving the plexus, the vagus

passes onto the anterior surface of

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the esophagus and takes part in

the formation of the esophageal

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plexus.

Nerves in mediastinum
? The right phrenic nerve

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descends in the thorax along the

right side of the right

brachiocephalic vein and the

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superior vena cava .

? It passes in front of the root of

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the right lung and runs along the

right side of the pericardium, which

separates the nerve from the right

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atrium.

? It then descends on the right side

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of the inferior vena cava to t`he

diaphragm.

? Its terminal branches pass through

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the caval opening in the

diaphragm to supply the central

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part of the peritoneum on its under

aspect.

Nerves in mediastinum

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? The left phrenic nerve descends

in the thorax along the left side of

the left subclavian artery.

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? It crosses the left side of the aortic

arch and here crosses the left side

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of the left vagus nerve.

? 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

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the left ventricle.

? On reaching the diaphragm, the

terminal branches pierce the

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muscle and supply the central part

of the peritoneum on its under

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aspect.
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 the

mediastinum 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 trachea

and 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 esophagus

may 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 can

partially 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 be

seen 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

pleural cavities.

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?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

explored down to the region of

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the bifurcation of the trachea.

?The procedure can be used to

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determine the diagnosis and

degree of spread of carcinoma

of the bronchus.

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Summary
? Mediastinum: definition
? Extend and sub

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divisions

? Contents
? Nerves passing thorax
? Clinical correlations

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