Final answer:
The ability of the lungs to expand is influenced by resistance, surface tension, and thoracic wall compliance.
Step-by-step explanation:
The ability of the lungs to expand is influenced by three main factors: resistance, surface tension, and thoracic wall compliance.
- Resistance: Resistance is the force that slows down the flow of gases. The size of the airway, specifically the diameter, is the primary factor affecting resistance. A smaller diameter forces air through a smaller space, resulting in more collisions with the walls of the airways.
- Surface Tension: Surface tension within the alveoli, caused by water present in the lining, tends to inhibit their expansion. However, pulmonary surfactant secreted by type II alveolar cells helps reduce this surface tension and prevents the alveoli from collapsing during expiration.
- Thoracic Wall Compliance: The ability of the thoracic wall to stretch while under pressure is known as thoracic wall compliance. If the tissues of the thoracic wall are not very compliant, it becomes difficult to expand the thorax and increase the size of the lungs.