Mediastinum

Dr.Hassan Shaibah

Chest Cavity

Pleurae & lungs Mediastinum pleurae &

lungs

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pleurae & lungspleurae & lungs

Chest Cavity

Med

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Mediastinum

• Extends superiorly to the thoracic outlet ,root of the neck &inferiorly to the diaphragm.

• extends anteriorly to the sternum & posteriorly to the vertebral column.

It contains :• thymus, trachea, thoracic duct ,the heart

esophagus, large blood vessels, lymph nodes, vagus & phrenic nerves, & sympathetic trunks.

thymus

large blood vessels

phrenic& vagus nerves

Heart

trachea

Some ContentsMediastinum

large blood vessels

phrenic& vagus nerves

trachea

Some ContentsMediastinum

esophagus

The mediastinum is divided by an imaginary plane passing from sternal angle to the Intervertebral discs T4 & T5

into: 1. superior mediastinum2. inferior mediastinum

MediastinumDivsion

sternal angle

superior

inferior

4

5

The inferior mediastinum

subdivided into: 1. anterior mediastinum, a space between the

pericardium and the sternum2. Middle mediastinum pericardium and heart3. posterior mediastinum, between

“pericardium &vertebral column”

MIDDLE

Anterior

Posterior

*

*inferior

mediastinumm

superior

Superior Mediastinum

is bounded:• front by manubrium sterni• behind by first 4 thoracic vertebrae.It contains: • (a) Thymus, (b) large veins, (c) large arteries,

(d) trachea, (e) esophagus and thoracic duct, (f) nerves

1

4

manubrium

thymus

RT & LT brachiocephalic v.

BrachiocephalicTrunk

LT common carotid a. nerves

5

12

front Body of sternum

Inferior Mediastinum Bondries

behind lower 8 thoracic

vertebrae

Inferior Mediastinum

It contains: (a) Thymus, (b) heart within the pericardium. (c) phrenic nerves(d) esophagus and thoracic duct, (e) descending aorta(f)Azygous venous system (g) sympathetic trunks

1)Thymus

2)heart within the

pericardium

3)esophagus

4)phrenic nerves

5)Descending aorta

6)Thoracic duct

Sympathetic trunks

Anterior mediastinum, a space between the pericardium and the sternum

Middle mediastinum pericardium and heart will be discussed with Cardiovascular block

Posterior Mediastinum Boundaries:

.

Ant. pericardium

Inf. diaphragm

Sup. transverse thoracic plane

Post. bodies of the vertebral column

5

12

laterally the pleura (on either side)

Contents

1)Descending aorta

3)Thoracic duct

2)Azygos venous system

Sympathetic trunks

9)vagus nerve

Vagal plexus

Contents

• artery – descending thoracic aorta

• Veins– azygos vein– the sup. & inf. hemiazygos vein

• nerves – vagus nerve– Sympathetic trunks

• esophagus• thoracic duct

Azygos Venous system:consist of:

1. azygos v.

3)Inferior hemiazygos

v.

2)superior hemiazygos v.

They drain blood from:• posterior intercostal spaces • posterior abdominal wall• pericardium• diaphragm• bronchi• esophagus.

Azygos Veinformed by union of:

Azygos V.

1)right subcostal v.  

2)right ascending lumbar v.

T5

SV

CIV

C

Tributaries:

8 lower right posterior intercostal v.

RT superior intercostal v.

Mediastinal veins.

Superiorhemiazygos veins.

Inferiorhemiazygos veins

1)Azygos Vein

formed by union of the right ascending lumbar vein and the right subcostal vein.

b. It ascends through aortic opening in the diaphragm on the right side of the aorta to the level of the fifth thoracic vertebra.

• Arch over the root of the right lung to empty into the SVC

e. The azygos vein tributaries are:

a. The 8 lower right posterior intercostal veins.b. The right superior intercostal vein.c. The superior and inferior hemiazygos veins.d. Mediastinal veins.

Inferior Hemiazygos Vein

• It is formed by the union of the left ascending lumbar vein & left subcostal vein.

• It ascends through the left crus of the diaphragm at T8.

• turns to the right and joins the azygos vein. • It receives as tributaries some lower left

intercostal veins and mediastinal veins.

Superior Hemiazygos Vein

• It is formed by the union of the 4 to the 8 intercostal veins.

• It joins the azygos vein at the level of the T7.

Mediastinum lymph

• Lymph nodes draining the lungs, mediastinal structures empty into the :

bronchomediastinal trunks & thoracic duct.

Thoracic Duct

begins in the abdomen as a dilated sac (cisterna chyli)

• Asend to the root of the neck to empty into beginning of the left Brachiocephalic vein

cisterna chyli

left Brachiocephalic v.

At the root of the neck, the thoracic duct receives:

.

1)left jugular trunk

2)LTSubclavian

trunk

3) broncho-mediastinal lymph

trunks.

The thoracic duct carries lymph from:

• i. The lower limbs.• ii. The pelvic cavity.• iii. The abdominal cavity.• vi. The left side of the thorax.• v. The left side of the head, neck.• vi. The left arm.

Right Lymphatic Duct formed by:

It opens into beginning Right brachiocephalic vein.

1)RT jugular

2)RTsubclavian

3)bronchomediastinal trunks

Thoracic Part of the Sympathetic Trunk 1. continuous above with the cervical and below

with the lumbar parts of the sympathetic trunk. 2. It is the most laterally placed structure in the

mediastinum.3. It runs downward on the heads of the ribs. 4. It leaves the thorax on the side of the body of

the T12 by passing behind the medial arcuate ligament.

5.. The sympathetic trunk has 12 (often only 11) segmentally arranged ganglia, each with white and gray ramus communicans passing to the corresponding spinal nerve.

6. The first ganglion is often fused with the inferior cervical ganglion to form the stellate ganglion.

1. The thymus is a flattened,

bilobed structure.2. It lies between the sternum &

pericardium in the anterior mediastinum.

3. In newborn infant, it reaches its largest size so it may extend up through the superior mediastinum in front of the great vessels into the root of the neck.

4. It continues to grow until puberty but thereafter undergoes involution

Thymus

• 5. It has a pink, lobulated appearance.

• 6. It is the site for development of T (thymic) lymphocytes.

Blood Supply• The blood supply of

the thymus is from the inferior thyroid & internal thoracic arteries.

Large Veins of the Thorax

1. Brachiocephalic Veins:a. The right brachiocephalic vein is formed by union of

right subclavian & right internal jugular veins. begins posterior to the sternoclavicular joint of the right

clavicle, and descends almost vertically to join the left brachiocephalic vein, forming superior vena cava

Its tributaries vertebral, internal thoracic, inferior thyroid sometimes

the first right posterior intercostal veins.

b. The left brachiocephalic vein.• It is formed by the union of the left subclavian and the right

internal jugular veins. • begins posterior to the sternoclavicular joint of left clavicle• * It passes obliquely behind the manubrium sterni and in front

of the large branches of the aortic arch. • * sternal end of the first right costal cartilage it joins the right

brachiocephalic vein to form the superior vena cava Its tributaries vertebral, internal thoracic, inferior thyroid, superior intercostal,

sometimes the first left posterior intercostal, thymic and pericardial veins.

2. Superior Vena Cava:

• It contains all the venous blood from head and neck and both upper limbs.

• It is formed by the union of the two brachiocephalic veins.

• It passes downward to end in the right atrium of the heart.

• The azygos vein joins the posterior aspect of the superior vena cava just before it enters the pericardium.