What are the pleural cavities and what are their layers?

The pleural cavities are potential spaces in the thorax that surround each lung. They are formed by two continuous serous layers: the visceral pleura (inner layer, adherent to the lung) and the parietal pleura (outer layer, lining the thoracic cavity).

What is the difference between visceral and parietal pleura in terms of nerve supply and sensitivity?

The visceral pleura is supplied by autonomic nerves (T2–T5) and is insensitive to pain. In contrast, the parietal pleura has somatic nerve supply (intercostal and phrenic nerves) and is sensitive to pain.

What are pleural recesses and why are they clinically important?

Pleural recesses are reserve spaces where the parietal pleura is not occupied by the lung during quiet breathing. Key recesses include the costodiaphragmatic recess (most dependent area, where pleural effusion first collects) and the costomediastinal recess (used to detect superficial cardiac dullness).

How does the nerve supply of the parietal pleura vary by region?

The parietal pleura has somatic nerve supply that varies by region: costal and peripheral diaphragmatic pleura are supplied by intercostal nerves, while mediastinal and central diaphragmatic pleura are supplied by the phrenic nerve.

What are the key clinical conditions associated with the pleura?

Common clinical conditions include pleurisy (inflammation of the parietal pleura, causing pain with breathing), pleural effusion (fluid accumulation, often first in the costodiaphragmatic recess), and pneumothorax (air in the pleural cavity, which can shift the mediastinum in tension pneumothorax).

What is the pulmonary ligament and what is its function?

The pulmonary ligament is a vertical pleural fold extending from the hilum to the diaphragm. It provides space for pulmonary veins to expand and allows descent of the lung root during inspiration.

How do the inferior borders of the lung and pleura compare in surface markings?

The inferior border of the lung lies higher than the inferior limit of the pleura. For example, at the midclavicular line, the lung is at the 6th rib and the pleura at the 8th rib; at the midaxillary line, lung at 8th rib and pleura at 10th rib; lateral to erector spinae, lung at 10th rib and pleura at 12th rib.

Pleura – Cavities, Recesses & Clinical Notes

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