Final answer:
The alveolar concentration (FA) is determined by factors such as the partial pressure of oxygen, airway resistance, the presence of pulmonary surfactant, and the regulation of blood flow in response to changes in oxygen, carbon dioxide, and pH levels.
Step-by-step explanation:
Factors that determine alveolar concentration (FA) include the partial pressure of oxygen, airway resistance, surface tension within the alveoli, and the presence of pulmonary surfactant. The formula F = ΔP/R helps describe the relationship between airway resistance and pressure changes, where ΔP is the pressure difference across the airways and R is the resistance. Small airway diameter increases resistance, leading to more effort required for ventilation. Pulmonary surfactant produced by type II alveolar cells reduces the surface tension caused by water in the alveoli lining, which otherwise would hinder alveolar expansion and can lead to collapse during expiration.
During breathing, the composition of alveolar air and atmospheric air differs, especially with regards to water vapor, carbon dioxide, and oxygen levels. When ventilation is sufficient, the partial pressure of oxygen in the alveoli remains high, facilitating efficient oxygen diffusion across the respiratory membrane. In contrast, with insufficient ventilation, the partial pressure drops, and the body compensates by redirecting blood flow to better-ventilated alveoli, which is influenced by factors like carbon dioxide, oxygen, and pH levels. This redirection is achieved through the dilation or constriction of pulmonary arterioles.