Anatomy of the Pleura

Anatomy of the
Pleura: Reflection
Lines and Recesses
François Bertin, MDa, Jean Deslauriers, MD, FRCS(C)b,*
The pleura is made of 2 serosal membranes, one
covering the lung (the visceral pleura) and one
covering the inner chest wall (the parietal pleura).
Their surfaces glide over each other, facilitating
proper lung movements during the various phases
of respiration. The transition between the parietal
and visceral pleura is at the pulmonary hilum or
root of the lung. At this level, the reflection covers
the constituents of the hilum, except inferiorly,
where the reflection extends down to the diaphragm
and is called the triangular or inferior
pulmonary ligament.
The parietal pleura is more complex anatomically
than the visceral pleura, as it covers
completely the inner surface of the thoracic wall
through which it is attached via a fibrous layer
known as the endothotracic fascia. The lines along
which the parietal pleura changes direction as it
passes from one wall of the pleural cavity to
another are called the lines of pleural reflection.
Because the lungs do not entirely fill the pleural
spaces during expiration, the potential spaces
thus created are called pleural recesses or sinuses.
These recesses fill with lung during inspiration.
Before the advent of antituberculous drugs, the
anatomy of pleural reflection lines and recesses
was of great importance to all surgeons involved in
the management of this disease, particularly those
performing operations pertinent to collapse therapy
such as extrapleural pneumonysis or apicolysis.1–3
Currently, thorough knowledge of this anatomy is
important for the correct interpretation of chest
radiographs, as well as for the performance of
procedures such as thoracentesis, tube drainage
of the pleural space, or pericardiocentesis.
LINES OF PLEURAL REFLECTION
AND TRIANGULAR LIGAMENTS
The lines of pleural reflection are formed by the
parietal pleura as it changes direction (reflects)
from one wall of the pleural cavity to another.
The sternal lines of reflection are where the
costal parietal pleura becomes continuous with
the mediastinal pleura. The external projection of
those lines is fairly similar on both sides and
extends from the level of the fourth costal cartilage
on the left side and sixth costal cartilage on the
right side to a point that lies approximately 3 to
4 cm above the anterior end of the first rib.
The costodiaphragmatic lines of reflection occur
where the costal parietal pleura joins the diaphragmatic
pleura inferiorly, and the vertebral lines of
reflection run in the paravertebral planes from the
first to the 12th thoracic vertebrae.
The parietal mediastinal pleura joins with the
visceral pleura on the medial aspect of the lung
at the level of the pulmonary hilum or root of the
lung. Before joining the parietal pleural, the visceral
pleura forms an almost circular sleeve that
encloses the structures of the hilum (Figs. 1
and 2). Below the root, the reflection of the mediastinal
pleura over the visceral pleura continues as
a double layer of pleura in the front and back of
the hilar plane. Together these 4 layers form a striplike
fold that crosses in a slightly oblique direction,