Pleural Cavity (Cavitas Thoracis)

It is a virtual slit-like space located between the parietal and visceral pleura that is 10–20 μm in size and contains few milliliters of serous fuid. The pleural serosa, by adapting to the anatomical elements that stand out inside the pleural cavity, forms depressions that are called sinuses or pleural recesses (recessus pleuralis). The most prominent and constant are as follows:

Pleural Apex or Superior Pleural Sinus [12–15]

It is a pleural cleft formed by the costal and mediastinal pleurae confuence. It occupies a cervical position forming the superior cone or dome, which is located above the clavicle, at the neck base.

To keep the pleural apex xed to the neck base, there are 3 ligaments that act as brous straps inserted through the external pleural face towards the neighboring bony structures, and which are collectively called the Sebileau suspensory apparatus (Fig. 29.11):

•\ Transverse-pleural ligament: It extends from the C7 vertebra transverse process to the pleural apex, and also emits an expansion towards the 1st rib. If it contains muscle bers it is called scalenus minimus muscle.

•\ Costo-pleural ligament: It extends from the neck and the 1st rib posteromedial border to the pleural apex.

•\ Vertebro-pleural ligament: It extends from the C7 vertebral body to the pleural apex.

Section of the three ligaments causes the pleural dome descent. This surgical maneuver called apicolysis was used in the past to carry out tuberculous cavern collapse therapy, when located in the upper lobe.

Anterior Costal-Phrenic Sinus or Cardio-Phrenic Sinus

Cleft that forms at the retrosternal level by the confuence or intersection between the costal, diaphragmatic and mediastinal pleurae. It has a trihedral angle appearance with some adipose content, with abundant lymphoid tissue from the thoracic and abdominal walls, as well as from the supramesocolic compartment. On the left side, it is located lateral to the heart up to 4 cm from the midsagittal line (Fig. 29.12).

Posterior Costal-Phrenic Sinus

Cleft is formed by the intersection of the diaphragmatic, costal and mediastinal pleurae, on the D11 vertebral body. It is the pleural cavity lowest point, and therefore the place where the fuid accumulated in the pleural cavity is deposited in pathological processes (Fig. 29.12).

Cost-Diaphragmatic Sinus or Lateral Cost-Phrenic Sinus

Pleural cleft is located between the diaphragm descending fanks and the chest wall. It is formed by the costal and diaphragmatic pleurae refection, adopting the appearance of a dihedral angle. It runs over the diaphragm costal insertions, surpassing them behind the arcuate ligament, with which it can go beyond the 12th rib lower border (Fig. 29.12).

Fissures18

They are depressions on the lung surface covered with visceral pleura, in the form of visceral pleura invaginations towards the lung parenchyma. They divide each lung into different lobes: three

Fig. 29.12  Thoracoscopic view of the right pleural cavity, (1) Pericardium, (2) diaphragm, (3) phrenic nerve and pericardiophrenic vein, (4) cardiophrenic sinus, (5) poste-

rior costophrenic sinus, (6) lateral costophrenic sinus, (7) major ssure, (8) minor ssure, RUL right upper lobe, RLL right lower lobe, ML middle lobe

in the right lung and two in the left. There may be anomalies in the number of cracks, both due to excess and defect (Fig. 29.12).

•\ Major ssure, oblique: Presents an oblique trajectory, from the fourth dorsal vertebra level to the end of the fth intercostal space. In the right lung, it begins at fourth rib neck levels, follows an oblique path downwards and forwards to reach the fth intercostal space diaphragmatic face. In depth, it crosses from lateral to medial and reaches the pulmonary hilum anterior and inferior part.

At the posterior and superior part, it separates the superior lobe from the inferior lobe, while in the anterior and inferior part, it separates the inferior lobe from the middle lobe.

In the left lung, there is only a major s- sure, and it has a slightly different path as it descends in the form of an italic ʃ from its uppermost part to the anterior and lower part.

•\ Minor ssure, horizontal: It only exists on the right side , begins at the fourth intercostal space level, and ascends slightly until it ends at the third intercostal space level. It runs forward in depth and medially reaches the hilum anterior part, separating the upper lobe from the middle lobe.

•\ Superior and inferior accessory ssures: the superior or azygos ssure originates from the azygos vein arch, which, during its embryonic development, splits the upper lobe mesenchyme into two parts: a medial or Wrisberg azygos lobe and a lateral or superior lobe. Thisssural anomaly is often associated with the