Final answer:
In a healthy person, inhaled particles are mostly trapped and eliminated by the nasal cavity and the mucociliary escalator of the bronchi and bronchioles through mucus and cilia. These mechanisms warm, moisten, and remove particulates, protecting the lungs from damage and disease.
Step-by-step explanation:
How the Respiratory System Protects Itself
In a healthy person, most of the particles that are inhaled into the respiratory system are trapped and eliminated by various protective mechanisms within the respiratory tract. When air is inhaled through the nose, the nasal cavity with its mucus and hairs captures particulate matter such as dust, viruses, and bacteria. This initial barrier is vital for preventing potential lung damage or triggering allergic responses.
If particles bypass the nose or enter through the mouth, the lower respiratory tract continues to provide defense. The bronchi and bronchioles contain mucus and cilia – tiny hair-like projections that line these airways. They work collectively, forming what is known as the mucociliary escalator, to move trapped particles and pathogens away from the lungs. Mucus captures the particulates and the cilia beat rhythmically to propel the mucus towards the throat, where it's eventually swallowed and processed through the digestive system.
Additionally, air is warmed and moistened in the nasal passages to prevent damage from cold, dry air. The body's natural defenses, such as the mucociliary escalator and immune responses, help to protect against respiratory diseases caused by inhaled pollutants and pathogens. Nonetheless, some small particles called PM10s and PM2.5s can penetrate deep into the lungs and have been linked to respiratory diseases like pneumonia, bronchitis, and asthma.