•\ Leukocytes production under infammatory stimulus.

•\ Phagocytosis.

•\ Trapping particles and macrophages.

Pleura Macroscopic Anatomy

After birth, the pleural space is a cavity in continuous movement with a 10–20 μm separation between the parietal and visceral serosa [11]. It is known that, to favor the movement of the lungs located inside this space, small amounts of pleural fuid rich in hyaluronic acid (0.1–0.2 mL/kg) are contained, which is essential for lubrication between the pleural serosa and maintain surface tension between them.

The pleura, being arranged as a covering sheet, does not have its own shape, rather it adapts by covering the intra-thoracic elements that protrude and make relief towards the pleural cavity interior. Its 20–40 μm thickness [6] explains its transparency, which allows the elements it covers to be seen through it (bones, vessels, muscles, fat, nerves, lung, pericardium...). The pleural free surface is smooth, polished, and shiny to the point that it refects light from the thoracoscope.

In the pleura, we distinguish two parts or territories that recall its embryonic origin: visceral pleura (splanchnopleura) and parietal pleura (somatopleura) in which three zones are considered: costal, mediastinal, and diaphragmatic pleura (Fig. 29.8).

Visceral Pleura (Pleura Visceralis or Pulmonalis)

It is 20 μm thick [12–15], intimately attached to the lung external surface, without a detachment or cleavage plane with parenchyma periphery, so it cannot be dissected without injuring the organ. The visceral serosa runs through all lung reliefs, penetrating to the depth of the ssures. Through it, the subpleural lymphatic canaliculi are visualized and identi ed, adopting a reticular distribution with a dark blue color due to inhaled foreign

1

2

3

4

5

6

Fig. 29.8  References (1, 2, 3 and 4) for ribs Iª, IIª, IIIª, y IVª; (5) Intercostal spaces; (6) Visceral pleura for the right upper lobe

particles accumulation (physiological anthracosis), which in turn delimit small areas of polygonal appearance or pulmonary lobules [12–15].

The visceral serosa is arranged as a mesothelial cells monocellular layer, which externally lines the lung surface. Immediately below, it extends a brous and elastic connective tissue layer that externally surrounds the peripheral pulmonary alveoli, emitting radially directed expansions or connective septa, which go deep towards the lobar pulmonary hilum.

On the lung medial side, and at the pulmonary hilum level, the pulmonary serosa refects on itself without loss of continuity, to continue imperceptibly with the mediastinal parietal pleura, forming the refection of the mediastinal pleura (Fig. 29.9).

Parietal Pleura (Pleura Parietalis)

It is 30–40 μm thick [12–15]. It covers and lines the pleural cavity internally, it remains loosely adhered to the endothoracic fascia from which it is easily dissected for surgical convenience, while there is no dissection plane at the level of the diaphragm muscle tendinous center, where the pleura is practically inseparable from the arcuatebers. According to the topographical zone that it covers, 3 portions are distinguished: costal, diaphragmatic and mediastinal:

Fig. 29.11  Right ápex parietal pleura view, (1, 2) y (3) suspensory ligaments of the right pleural dome, (4) second rib, (5) brachiocephalic arterial trunk, (6) right sub-

clavian artery, (7) right carotid artery, (8) internal thoracic artery, (9) intercostal artery, (10) costal pleura, (11) left pericardium phrenic artery