Download MBBS Anatomy PPT 62 Mediastinum Notes

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Learning Objectives

? Identify the divisions of the mediastinum and describe

their contents.

? Describe the gross anatomy of structures in

mediastinum.

? Describe the anatomy of nerves in the mediastinum.

? Correlate this knowledge to clinical conditions.

Boundaries of mediastinum

Thoracic inlet

Sternal Angle

sternum

Thoracic vertebra

Thoracic oulet
TS: Mediastinum

CS: Mediastinum

Mediastinum

? Bulky septum

between the

pleural cavities

& lungs

Extends-

? Root of the

neck to

diaphragm

? From the

sternum to

vertebral

column
Divisions of mediastinum

? Divided by an imaginary horizontal plane from

the sternal angle to the intervertebral disc

between 4th & 5th vertebra in to

? superior mediastinum
? Inferior mediastinum ?

Anterior Middle Posterior
DIVISIONS OF MEDIASTINUM

Boundaries Of Superior Mediastinum

BOUNDARIES:
? Anterior: manubrium sterni
? Posterior: Upper 4 thoracic vertebrae
? Superior: Plane of thoracic inlet
? Inferior: Horizontal plane
? On each side: Pleura
Superior mediastinum

SUPERIOR MEDIASTINUM


SUPERIOR MEDIASTINUM



LEFT

RIGHT
Superior mediastinum

? Posterior to the sternum & anterior to the

bodies of first four thoracic vertebra

Superior mediastinum

CONTENTS:

? FROM BEHIND FORWARD:

1.Esophagus

2.Trachea

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

left common carotid & left subclavian arteries

4.Right & left brachiocephalic veins & superior vena

cava

5.Thymus gland
Other Contents of superior mediastinum

Nerves:

1. Right & left vagus

2. Right & left phrenic

3. Right & left

sympathetic trunks

4. Left recurrent

laryngeal

Lymphatic structures:

1. Thoracic duct

2. Lymph nodes

Thymus

? Asymmetric bilobed gland

? Upper extent may reach as high as thyroid

gland

? Involved in early development of immune

system

? Large in children

? Atrophies after puberty
Brachiocephalic veins

?Located immediately

posterior to thymus

?Formed at the jn. of IJ

& subclavian veins.

? Begins post to clavicle

?Tributaries: vertebral,

first post. Intercostal,

int. thoracic, inf.

Thyroid, thymic veins

Left superior intercostal vein

? Drains upper two

or three

intercostal veins,

left bronchial

veins & left

pericardiophrenic

veins

? Drains in to left

brachiocephalic

veins
Superior vena cava

? Vertically oriented
? Begins posterior

to the lower edge

of first costal

cartilage

? terminates at the

lower border of

right third costal

cartilage

Arch of aorta & it's branches

? Begins when

ascending aorta

emerges from

pericardial sac

? Terminates on left side

of vertebral level

between Th 4th - 5th

Branches-

Brachiocephalic trunk

Left CCA
Left subclavian

Thyroid ima
Trachea

? Midline structure
? Present anterior to

esophagus

? Swallowing, breathing,

disease & specialized

instrumentation causes

shift of trachea

? divides just inferior to

sternal angle (T3- T4)

into Right & Left principal

bronchus

Vagus nerve

Right Vagus
? lies between right

brachiocephalic

vein & trunk

? Descends

posteriorly to the

root of Right lung

to reach

esophagus

? Gives branches to

esophagus,

cardiac plexus &

pulmonary plexus
Left Vagus nerve

? Lies between Lt CCA &

Lt subclavian artery

? Pass posterior to the

root of lung to reach the

esophagus

? Gives branches to

esophagus, cardiac &

pulmonary plexus

? Also gives Lt recurrent

laryngeal nerve- arise at

inferior margin of arch of

aorta, winds around the

aorta & reaches the

groove between

esophagus & trachea

Left recurrent laryngeal nerve

? arise at inferior

margin of arch of

aorta, winds around

the aorta & reaches

the groove between

esophagus &

trachea
Phrenic nerve

? Right Phrenic ?enters

lateral to Right Vagus

& beginning of Right

brachiocephalic vein

? continues inferiorly on

the Right side of sup

vena cava, on

entering middle

mediastinum

descends along the

Rt side of pericardial

sac anterior to the Rt

lung root

? leaves the thorax with

inferior vena cava

Left phrenic nerve

? enters similar to

Right Phrenic nerve

? Lateral to Vagus & Lt

brachiocephalic vein

? Descends on left

lateral surface of

arch of aorta

? Passes superficial to

Lt vagus & superior

intercostal vein
Left phrenic nerve

? In middle

mediastinum lies on

the Lt side of

pericardial sac

anterior to root of Lt

lung

? Pierces the

diaphragm near the

apex of the heart

Thoracic duct

? Major lymphatic vessel

of the body

? Enters sup.

mediastinum from

below at the level of

T4/5

? continues through the

superior med. posterior

to arch of aorta

between the esophagus

& Lt pleura


Anterior Mediastinum

Lies ant. to pericardium
Boundaries:

Anterior: body of sternum

Posterior: pericardium

superior: imaginary line

separating sup. &

inf.mediastinum

Infreior: diaphragm

Lateral: mediastinal pleura
Anterior mediastinum

Thymus

contains:

Lymph nodes
fat

Thymus

Located in anterior

mediastinum.
Develops from endoderm

of 3rd pharyngeal pouch

Present in childhood,

involutes in adults
Blood supply

Arterial :i nt. Mammary arteries

Venous: internal thoracic veins

Lymphatic drainage: lower

cervical, int. Mammary and hilar

nodes
Esophagus

? Starts at the C6th &

terminates at cardiac

opening of stomach

(T12)

? Descends anterior to

vertebral bodies in

midline

? Crossed laterally by the

azygos vein on the right

side & arch of aorta on

the left side

Posterior Mediastinum

BOUNDARIES:
? Anterior: Pericardium & diaphragm
? Posterior: Lower 8 thoracic vertebrae
? Superior: Horizontal plane
? Inferior: Diaphragm
? On each side: Pleura
Posterior Mediastinum

? CONTENTS:

1. Esophagus (most anterior structure)

2. Thoracic duct

3. Right & left vagus

4. Descending aorta

5. Azygos & hemiazygos veins

6. Right & left sympathetic trunks & their

branches (splanchnic nerves)

7. Lymph nodes

POSTERIOR MEDIASTINUM
POSTERIOR MEDIASTINUM

POSTERIOR MEDIASTINUM
POSTERIOR MEDIASTINUM

POSTERIOR MEDIASTINUM


MIDDLE MEDIASTINUM

? CONTENTS:

1. Pericardium & heart

2. Arteries: ascending aorta, pulmonary trunk

3. Veins: lower half of superior vena cava,

terminations of inferior vena cava & pulmonary

veins

4. Nerves: phrenic

5. Lymph nodes

Mediastinum
VEINS

BRACHIOCEPHALIC: (Superior mediastinum)

? FORMATION: by union of internal jugular & subclavian vein

(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

right phrenic nerve & right pleura & lung, its tributaries in thorax:

right 1st posterior intercostal vein, right internal thoracic vein,

right lymphatic duct

? LEFT VEIN: longer & has an oblique course, related anteriorly to

manubrium & thymus gland, & posteriorly to branches of arch of

aorta, its tributaries in thorax: left 1st posterior intercostal vein,

left superior intercostal vein, left internal thoracic vein, thoracic

duct

VEINS

SUPERIOR VENA CAVA: (Superior & middle mediastinum)

? FORMATION: by union of brachiocephalic veins, behind lower border of

right 1st costal cartilage

? END: opens into right atrium behind right 3rd costal cartilage
? TRIBUTARIES: azygos vein


AZYGOS & HEMIAZYGOS VEINS

VEINS
AZYGOS VEIN: (Posterior mediastinum)

?

ORIGIN: by union of right ascending lumbar & subcostal veins

(passes through aortic opening of diaphragm)

?

END: forms an arch above the root of right lung & ends in S.V.C.

opposite lower border of T4

?

RELATIONS:

1. Anterior: esophagus

2. Posterior: thoracic vertebra

3. Right: right pleura & lung

4. Left: thoracic duct

?

TRIBUTARIES: superior & inferior hemiazygos veins, right

superior intercostal vein, right posterior intercostal veins (from

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

INFERIOR HEMIAZYGOS: (Posterior

mediastinum)

?ORIGIN: by union of left ascending lumbar

& subcostal veins (passes through left crus

of diaphragm)

?END: into azygos vein, opposite T8

?TRIBUTARIES: left posterior intercostal

veins (9th to 11th), esophageal veins

VEINS

SUPERIOR HEMIAZYGOS: (Posterior mediastinum)

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

? END: into azygos vein, opposite T7

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

? END: passes through vena caval opening of diaphragm

& opens into right atrium behind right 6th costal

cartilage
Ar
A te

ORT rAi:

?

ASCEND e

IN s

G AORTA: (Middle mediastinum)

1. ORIGIN: at the base of left ventricle opposite lower border of left 3rd

costal cartilage

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

aorta

3. BRANCHES: right & left coronary arteries

Ar
? te

ARrCieH sOF AORTA: (Superior mediastinum)

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

right 2nd costal cartilage

2. COURSE & RELATIONS: ascends upward backward & to the left

(behind manubrium & in front of trachea) then curves backward (to

the left of trachea) then final y curves downward

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

of T4
Ar
?

teBRArNiCHeESs OF ARCH OF AORTA: (Superior mediastinum)

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

left brachiocephalic vein & in front of trachea) & divides

into right common carotid & right subclavian arteries

(behind right sternoclavicular joint)

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

the left side of brachiocephalic artery) & enters the neck

(behind left sternoclavicular joint)

3. LEFT SUBCLAVIAN: ascends upward (behind left common

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

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

Ar
DES te

CENDI rNie

G AO sRTA: (Posterior mediastinum)

?

ORIGIN: continuation of arch of aorta

?

TERMINATION: passes through aortic opening of

diaphragm (opposite T12) & continues as abdominal aorta

?

RELATIONS:

1. Anterior: esophagus

2. Posterior: thoracic vertebrae

3. Right: thoracic duct

4. Left: left pleura & lung

?

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

subcostal, bronchial, esophageal, pericardial arteries
Ar
PUL te

MON rARiYe TRsUNK (Middle mediastinum)

? ORIGIN: from upper part of right ventricle, behind

sternal end of left 3rd costal cartilage

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

lower border of T4) into:

1. Right pulmonary: runs behind ascending aorta &

S.V.C to enter root of right lung

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

enter root of left lung

T
? RAC

BEGIN H

NIN EA

G: continuation of larynx, opposite C6

? TERMINATION: bifurcates into 2 bronchi, opposite lower border

of T4

? RELATIONS: (in superior mediastinum)

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

arteries

2. Posterior: left recurrent laryngeal nerve, esophagus

3. Right: right vagus nerve

4. Left: arch of aorta, left subclavian artery

? NERVE SUPPLY: sympathetic trunks & vagus

? BLOOD SUPPLY: inferior thyroid vessels

? LYMPHATIC DRAINAGE: pretracheal & paratracheal
ESOP
? BEGINNI H

NG: AG

contin UuatiSon of pharynx, opposite C6

? TERMINATION: passes through esophageal opening of diaphragm

(opposite T10) & joins stomach

? RELATIONS: (in superior mediastinum)

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

2. Posterior: thoracic vertebrae

3. Right: right pleura & lung

4. Left: thoracic duct, left pleura & lung

ESOP?RELATIHONAGS: (inU pSosterior mediastinum)

1.Anterior: pericardium, separating it from left atrium

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

3.Right: right pleura & lung

4.Left: descending aorta, left pleura & lung

? NERVE SUPPLY: as trachea

? ARTERIAL SUPPLY: descending aorta

? VENOUS DRAINAGE: azygos & hemiazygos

? LYMPHATIC DRAINAGE: posterior mediastinal lymph

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

L1 & L2)

? COURSE: passes through aortic opening of

diaphragm, ascends in posterior mediastinum

(behind esophagus) & in superior mediastinum (to

the left of esophagus) to enter root of neck

? END: in left brachiocephalic vein

? RELATIONS: ( in posterior mediastinum)

1. Anterior: esophagus

2. Posterior: thoracic vertebrae

3. Right: azygos vein

4. Left: descending aorta

THORACIC DUCT

TRIBUTARIES:

? It drains lymph from both sides of the body below

the diaphragm through cysterna chyli

? It drains lymph from left half of the body above

diaphragm through:

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

neck

2. Left subclavian lymph trunk: drains left upper limb

3. Left bronchomediastinal lymph trunk: drains left

side of thorax
RIGHT LYMPHATIC DUCT

? ORIGIN: formed by union of:

1. Right jugular lymph trunk: drains right

side of head & neck

2. Right subclavian lymph trunk: drains

right upper limb

3. Right bronchomediastinal lymph trunk:

drains right side of thorax

? END: in right brachiocephalic vein

NERVES
PHRENIC NERVES: (Superior & middle mediastinum)

?

ORIGIN: anterior rami of C3,4,5

?

COURSE & RELATIONS IN THORAX:

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

?

BRANCHES:

1. Motor branches to: diaphragm

2. Sensory branches from:

?

Mediastinal & central part of diaphragmatic pleura

?

Fibrous pericardium & parietal layer of serous pericardium

?

Peritoneum covering central part of undersurface of diaphragm
NERVES
? VAGUS NERVES: (Superior & posterior mediastinum)

? ORIGIN: 10th cranial nerve

? COURSE & RELATIONS IN THORAX:

1. RIGHT: descends to the right side of: trachea, behind

root of right lung (pulmonary plexus), behind

esophagus (esophageal plexus), passes through

esophageal opening of diaphragm to reach posterior

surface of stomach

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

root of left lung (pulmonary plexus), in front of

esophagus (esophageal plexus), passes through

esophageal opening of diaphragm to reach anterior

surface of stomach

NERVES

BRANCHES IN THORAX:

? BOTH VAGI: to lungs & esophagus

? RIGHT VAGUS: to heart

? LEFT VAGUS: left recurrent laryngeal nerve:

curves below arch of aorta, behind ligamentum

arteriosum, ascends in groove between trachea

& esophagus to reach the neck. It supplies: heart,

trachea, esophagus (in thorax) & larynx (in neck)
NERVES
THORACIC PART OF SYMPATHETIC TRUNKS: (Superior &

posterior mediastinum)

? BEGINNING: the cervical part continues as thoracic

part by passing in front of neck of first rib

? TERMINATION: the thoracic part continues as lumbar

part by passing behind medial arcuate ligament

? COURSE:

1. In upper part of thorax: descend in front of heads of

ribs

2. In lower part of thorax: descend on the sides of

bodies of vertebrae

? GANGLIA: usual y 11 (1st thoracic ganglion fuses with

inferior cervical ganglion forming stel ate ganglion)

NERVES

?

BRANCHES:

1. Rami communicantes: each ganglion receives a

white ramus (preganglionic) & gives a grey ramus

(postganglionic) to corresponding thoracic spinal

nerve

2. Visceral branches (postganglionic) to thoracic organs

(from upper 5 ganglia): to heart, lungs, esophagus,

descending aorta

3. Visceral branches (preganglionic) to abdominal

organs:

? Greater splanchnic nerve (from 5th to 9th ganglia)

? Lesser splanchnic nerve (from 10th 7 11th ganglia)

? Lowest splanchnic nerve (from 12th ganglion)


Nerves in mediastinum

? The right vagus nerve descends in

the thorax, first posterolateral to the

brachiocephalic artery then lateral

to the trachea

? Passes behind the root of the right

lung and assists in the formation of

the pulmonary plexus.

? On leaving the plexus, the vagus

passes onto the posterior surface of

the esophagus and takes part in the

formation of the esophageal

plexus.

? It then passes through the

esophageal opening of the

diaphragm.

Nerves in mediastinum
? The left vagus nerve descends in

the thorax between the left

common carotid and the left

subclavian arteries

? It then crosses the left side of the

aortic arch

? The vagus then turns backward

behind the root of the left lung and

assists in the formation of the

pulmonary plexus.

? On leaving the plexus, the vagus

passes onto the anterior surface of

the esophagus and takes part in

the formation of the esophageal

plexus.


Nerves in mediastinum
? The right phrenic nerve

descends in the thorax along the

right side of the right

brachiocephalic vein and the

superior vena cava .

? It passes in front of the root of

the right lung and runs along the

right side of the pericardium, which

separates the nerve from the right

atrium.

? It then descends on the right side

of the inferior vena cava to t`he

diaphragm.

? Its terminal branches pass through

the caval opening in the

diaphragm to supply the central

part of the peritoneum on its under

aspect.

Nerves in mediastinum
? The left phrenic nerve descends

in the thorax along the left side of

the left subclavian artery.

? It crosses the left side of the aortic

arch and here crosses the left side

of the left vagus nerve.

? It passes in front of the root of the

left lung and then descends over

the left surface of the pericardium,

which separates the nerve from

the left ventricle.

? On reaching the diaphragm, the

terminal branches pierce the

muscle and supply the central part

of the peritoneum on its under

aspect.

anatomical

Acc. To felson

Clinical correlations
? Deflection of Mediastinum
?If air enters the pleural

cavity (a condition called

pneumothorax), the lung

on that side immediately

collapses and the

mediastinum is displaced to

the opposite side.

?patient's being breathless

and in a state of shock; on

examination, the trachea

and the heart are found to

be displaced to the opposite

side


Clinical correlations
? Mediastinitis
?Deep infection of the neck spread readily into the thorax,

producing a mediastinitis.

?Penetrating wounds of the chest involving the esophagus

may produce a mediastinitis.

Clinical correlations

? Mediastinal Tumors or Cysts
?Enlargement of mediastinal tumor

may compress the left recurrent

laryngeal nerve, producing

paralysis of the left vocal fold.

?An expanding cyst or tumor can

partially occlude the superior vena

cava, causing severe congestion

of the veins of the upper part of

the body.

?Other pressure effects can be

seen on the sympathetic trunks,

phrenic nerves, and sometimes

the trachea, main bronchi, and

esophagus.


Clinical correlations
? Mediastinoscopy

?diagnostic procedure by which

tracheobronchial lymph nodes

are obtained without opening the

pleural cavities.

?A small incision is made in the

midline in the neck just above

the suprasternal notch, and

the superior mediastinum is

explored down to the region of

the bifurcation of the trachea.

?The procedure can be used to

determine the diagnosis and

degree of spread of carcinoma

of the bronchus.

Summary
? Mediastinum: definition
? Extend and sub

divisions

? Contents
? Nerves passing thorax
? Clinical correlations

This post was last modified on 05 April 2022