Human Anatomy Vol 1

INIRODUCTION
Mediastinum (Latin intermediate) is the middle space
left in the thoracic cavity inbetween the lungs. Its most
important content is the heart enclosed in the peri-
cardium in the middle part of the inferior mediastinum
or the middle mediastinum. Above it, lies superior
mediastinum. Anterior and posterior to the heart are
anterior mediastinum and posterior mediastinum
respectively.
The mediastinum is the median septum of the thorax
between the two lungs. It includes the mediastinal
pleurae (Figs 15.5 and 15.8).

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Reflect the upper half of manubrium sterni upwards and

study the boundaries and contents of superior and three

divisions of the inferior mediastinum.

Boundories

Anteriorly: Stemum

P osteriorly : Vertebral column

Super iorly : Thoracic inlet

lnferiorly: Diaphragm

On each side: Mediastinal pleura.

Divisions

For descriptive purposes the mediastinum is divided
into the superior mediastinum and the inferior medi-
astinum. The inferior mediastinum is further divided
into the anterior, middle and posterior mediastinum
(Fig. 17.1).
The superior mediastinum is separated from the
inferior by an imaginary plane passing through the
sternal angle anteriorly and the lower border of the

Vertebral column

lnlet of thorax

Superior mediastinum

Manubrium

lnferior mediastinum

Branches of internal

thoracic artery

Body of sternum

Anterior Mediostinum

Sternopericardial ligament

Xiphisternum

Diaphragm

Middle Mediostinum

Posterior mediastinum

Fig. 17.1 : Subdivisions of the mediastinum

body of the fourth thoracic vertebra posteriorly. The

inferior mediastinum is subdivided into three parts by

the pericardium. The area in front of the pericardium

is the anterior mediastinum. The area behind the

pericardium is the posterior mediastinum. The

pericardium and its contents form the middle medi-

astinum.

Boundories

Anteriorly : Manubrium sterni (Fig. 17.1).

Pasteriorly: Upper four thoracic vertebrae

Superiorly:Plane of the thoracic inlet

I riorly: An imaginary plane passing through the

sternal angle in front, and the lower border of the body

of the fourth thoracic vertebra behind.

On each side: Mediastinal pleura.

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