CBSE Class 10 Answered

The liquid present in the pleural cavity is called pleural fluid.

Composition of pleural fluid:

• 75% macrophages
• 23% lymphocytes
• (1% to 2%) mesothelial cells
• (1%) neutrophils
• (0%) eosinophils

Functions of pleural fluid:

• It acts to lubricate the pleural surfaces.
• This lubrication reduces friction between the two layers to prevent trauma during breathing.
• It creates surface tension that helps maintain the position of the lungs against the thoracic wall.
• The adhesive characteristic of the pleural fluid causes the lungs to enlarge when the thoracic wall expands during ventilation, allowing the lungs to fill with air.