Final answer:
The lungs stick to the thoracic cavity due to the thin layer of fluid between the covering membranes. This fluid reduces friction and protects the lung tissue during breathing. Pleurisy is a condition caused by inflammation of these layers, leading to pain and reduced lung volume.
Step-by-step explanation:
The lungs stick to the thoracic cavity because of the thin layer of fluid between the membranes covering them.
Each lung is surrounded by the visceral pleura, which covers the lung and dips into spaces, and the parietal pleura, which lines the interior of the thorax.
The space between these layers, called the intrapleural space, contains a small amount of fluid that reduces friction and protects the lung tissue as the lungs contract and relax.
Pleurisy can occur when these layers become inflamed, resulting in pain and reduced lung volume.