Human Anatomy Vol 1

INTRODUCTION
'Ihe spongy lungs occupying a major portion of thoracic

cavity are enveloped in a serous cavity-the pleural
cavity. There is always slight negative pressure in this
cavity. During inspiration the pressure becomes more
negative, and air is drawn into the lungs covered with
its visceral and parietal layers. Visceral layer is
inseparable from the lung and is supplied and drained
by the same alteries, veins and nerves as lungs. In a
sirnilar maRner, the parietal pleura follows the walls
of the thoracic cavity with cervical, costal, dia-
phraginatic and rnediastinal parts. Pleural cavity limits
the expansion of tl're lungs.

DISSECTION

Divide the manubrium sterni transversely immediately

inferior to its junction with the first costal cartilage. Cut

through the parietal pleura in the first intercostal space

on both sides as far back as possible. Cut sternum at

the level of xiphisternal joint. Use a bone cutter to cut

2nd to 7th ribs in midaxillary line on each side of thorax.

Separate intercostal muscles in 1-G spaces from

underlying pleura.

Lift the inferior part of manubrium and body of

sternum with ribs and costal cartilages and reflect it

towards abdomen. ldentify the pleura extending from

the back of sternum onto the mediastinum to the level

of lower border of head. Note the smooth surface of

pleura where it lines the thoracic wall and covers the

lateral aspeets of mediastinum. Trace the surface

marking of parietal pleura on the skeleton.

Remove the pleura and the endothoracic fascia from

the back of sternum and costal cartilages which is

reflected towards abdomen. ldentify the transversus

thoracis muscle and internal thoracic vessels.

Note the origin of diaphragm from the xiphoid process

and divide it. ldentify the course and branches of

intercostal nerve again. Trace the nerve medially

superficial to the Internal thoracic vessels.

Pull the lung laterally from the mediastinum and find

its root with the pulmonary ligament extending down-

wards from it. Cut through the structures, i.e. bronchus/

bronchi, pulmonary vessels, nerves, comprising its root

from above downwards close to the lung. Remove the

lung on each side. Be careful not to injure the lung or

your hand from the cut ends of the ribs.

ldentify the phrenic nerve with accompanying blood

vessels anterior to the root of the lung. Make a

longitudinal incision through the pleura only parallelto

and on each side of the phrenic nerve. Strip the pleura

posterior to the nerve backwards to the intercostal

spaces. Pull the anterior flap forwards to reveal part of

the pericardium with the heart. ldentify the following

structures seen through the pleura.

Right side

1. Bulge of the hearl and pericardium anteroinferior to
   the root of the lung (Fig. 15.1).


2. A longitudinal ridge formed by right brachiocephalic
   vein down to first costal cartilage and by superior
   vena cava up to the bulge of the heart.


3. A smaller longitudinal ridge formed by inferior vena
   cava formed between the heart and the diaphragm.


4. Phrenic nerve with accompanying vessels forming
   a vertical ridge on these two venae cavae passing
   anterior to root of the lung.


5. Vena azygos arching over root of the lung
   the superior vena cava.


6. Trachea and oesophagus posterior to the

to enter

phrenic

nerve and superior vena cava.

7. Right vagus nerve descending posteroinferiorly
   across the trachea, behind the root of the lung.

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