THORACIC CAVITY AND PLEURAE
Aspiration of any fluid from the pleural cavity is
called paracentesis thoracis.It is usually done in the
eighth intercostal space in the midaxillary line
(Fig. 15.9). The needle is passed through the lower
part of the space to avoid injury to the principal
neurovascular bundle, i.e. vein, artery and nerve
(vAN).
Some clinical conditions associated with the pleura
are as follows.
a. Pleurisy: This is inflammation of the pleura. It
may be dry, but often it is accompanied by
collection of fluid in the pleural cavity. The con-
dition is called the pleural effusion (Fig. 15.10).
Dry pleurisy is more painful because during
inspiration both layers come in contact and
there is friction.
b. Pneumothorax: Presence of air in the pleural
cavity.
c. Haemothorax: Presence of blood in the pleural
cavity.
d. Hydropneumothorax: Presence of both fluid and
air in the pleural cavity.
e. Empyema: Presence of pus in pleural cavity.
Costal and peripheral parts of diaphragmatic
pleurae are innervated by intercostal nerves (Fig.
15.11). Hence irritation of these regions cause
referred pain along intercostal nerves to throacic
or abdominal wall. Mediastinal and central part
of diaphragmatic pleurae are innervated by
phrenic nerve (C4). Hence irritation here causes
referred pain on tip of shoulders.
Pain on right shoulder occurs due to inflam-
mation of gallbladder, while on left shoulder is
due to splenic rupture.
Pleural effusion causes obliteration of costodia-
phragmatic recess.
Pleura extends beyond the thoracic cage at
following areas:
- Right xiphicostal angle
- Right and left costovertebral angles
- Right and left sides of root of neck as cervical
dome of pleura.
The pleura may be injured at these sites during
surgical procedures. These sites have to be
remembered.
During inspiration pure air is withdrawn in the
lungs. At the same time, deoxygenated blood is
received through the pulmonary arteries. Thus an
exchange of gases occurs at the level of alveoli.
The deoxygenatedblood gets oxygenated and sent
via pulmonary veins to the left atrium of heart.
The impure air containing carbon dioxide gets
expelled during expiration.
Fig. 15.9; Paracentesis thoracis
Atelectasis
(collapsed lung)
Fluid or air
accumulation
Cervical and
costal parts of
parietal pleura
innervated by
intercostal nerves
Visceral pleura
innerv6ted by
autonomic nerves
Mediastinal and
central diaphrag-
matic parts of
parietal pleura
innervated by
phrenic nerve
Fig. 15.11: Nerve supply of parietal pleura. Costal pleura and
cervical pleura innervated by intercostal nerues, mediastinal
pleura and most of diaphragmatic pleura innervated by
phrenic nerve
Fig. 15.10: Pleural effusion
