Human Anatomy Vol 1

-Anonymous

INTRODUCTION

The lungs occupying major portions of the thoracic
cavity,leave little space for the heart, which excavates
more of the left lung. The two lungs hold the heart tight
between them, providing it the protection it rightly
deserves. There are ten bronchopulmonary segments
in each lung.
The lungs are a pair of respiratory organs situated
in the thoracic cavity. Each lung invaginates the
corresponding pleural cavity. The right and left lungs
are separated by the mediastinum.
The lungs are spongy in texture. In the young, the
lungs are brown or grey in colour. Gradually, they
become mottled black because of the deposition of
inhaled carbon particles. The right lung weighs about
700 g,; it is about 50 to 100 g heavier than the left lung.

DISSECIION

ldentify the lungs by the thin anterior border, thick

posterior border, conical apex, wider base, medial

surface with hilum and costal surface with impressions

of the ribs and intercostal spaces. ln addition, the right

lung is distinguished by the presence of three lobes,

whereas left lung eomprises two lobes only.

On the mediastinal part of the medial surface of right

lung identify two bronchi-the eparterial and hyparterial

bronchi, with bronchial vessels and posterior pulmonary

plexus, the pulmonary artery between the two bronchi

on an anterior plane. The upper pulmonary vein is

situated still on an anterior plane while the lower

pulmonary vein is identified lrelow the bronchi.

The impressions on the right lung are of superior

vena cava, inferior vena cava, right ventricle. Behind

the root of lung are the impressions of vena azygos

and oesophagus.

Hilum of the left lung shows the single bronchus

situated posteriorly, with bronchial vessels and posterior

pulmonary plexus. The pulmonary artery lies above the

bronchus. Anterior to the bronchus is the upper pul-

monary vein, while the lower vein lies below the

bronchus.

The mediastinal surface of left lung has the

impression of left ventricle, ascending aoda. Behind the

root of the left lung are the impressions of descending

thoracic aorta while oesophagus leaves an impression

in the lower part only.

Feolures

Each lung is conical in shape (Fig. 16.1). It has:

1 An apex at the upper end.

2 A base resting on the diaphragm.

3 Three borders, i.e. anterior, posterior and inferior.

4 Two surfaces, i.e. costal and medial. The medial

surface is divided into vertebral and mediastinal

parts.

The apex is blunt and lies above the level of the

anterior end of the first rib. It reaches nearly 2.5 cm

above the medial one-third of the clavicle, just medial

to the supraclavicular fossa. It is covered by the cervical

pleura and by the suprapleural membrane, and is

grooved by the subclavian artery on the medial side

and anteriorly.

The base is semilunar and concave. It rests on the

diaphragm which separates the right lung from the

right lobe of the liver, and the left lung from the left

lobe of the liver, the fundus of the stomach, and the

spleen.

The anteriorborder is very thin (Figs 76.2 and 16.3). It

is shorter than the posterior border. On the right side,

it is vertical and corresponds to the anterior or

costomediastinal line of pleural reflection. The anterior

border of the left lung shows a wide cardiac notch below

the level of the fourth costal cartilage. The heart and

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