What is pleura ? List its functions .

Explanation

### Step-by-Step Solution:

1. **Definition of Pleura**:
- The pleura is a double-layered peritoneal sac that surrounds the lungs. It consists of two membranes: the outer pleura (parietal pleura) that lines the thoracic cavity and the inner pleura (visceral pleura) that covers the lungs themselves.

2. **Pleural Cavity**:
- Between these two layers of pleura is the pleural cavity, which contains pleural fluid. This cavity is essential for the proper functioning of the lungs during respiration.

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