Question

Describe the fluids immediately inside and outside the lungs that make effective breathing possible. Your discussion should include the origin of the fluids and the mechanism by which each acts to allow for lung ventilation

Answer 1

The fluids immediately inside and outside the lungs are called as pleural fluid.

1. Pleural fluid is a serous fluid produced by the serous membrane covering normal pleurae.
2. It is a thin translucent fluid that fills the cavity between the parietal (outer) and visceral (inner) pleural layers surrounding the lungs.
3. The volume of fluid is small, roughly 1-10 ml
4. Most of the fluid is produced by the exudation in parietal circulation (intercostal arteries) via bulk flow and reabsorbed by the lymphatic system.
5. Thus, pleural fluid is produced and reabsorbed continuously.
6. The composition and volume are regulated by mesothelial cells in the pleura.
7. In a normal 70 kg human, a few milliliters of pleural fluid is always present within the intrapleural space.
8. Larger quantities of fluid can accumulate in the pleural space only when the rate of production exceeds the rate of reabsorption.
9. Normally, the rate of reabsorption increases as a physiological response to accumulating fluid, with the reabsorption rate increasing up to 40 times the normal rate before significant amounts of fluid accumulate within the pleural space.
10. Thus, a profound increase in the production of pleural fluid—or some blocking of the reabsorbing lymphatic system—is required for fluid to accumulate in the pleural space.

Pleural fluid functions by lubricating the space between the pleura, allowing the pleura to glide smoothly during inhalation and exhalation. In this way, it cushions delicate lung tissues against friction from the ribs and the chest wall itself.