The respiratory zone is the part of the airway where gas exchange takes place, allowing the body to trade waste carbon dioxide for fresh oxygen. Along with the conducting zone which draws air into the bronchial passages, it is part of the lower airway. Disorders of this region can include inflammation, neoplasms, and trauma, all of which can interfere with the ability to engage in gas exchange. This can quickly become fatal if left untreated.
This part of the respiratory tract starts with the respiratory bronchioles, which branch out into a number of structures known as alveolar ducts. These terminate in small sacks with a bubble-like appearance called alveoli. The sacs are richly supplied with deoxygenated blood from the heart. As the blood moves through the lungs, the thin membrane between the alveoli and the blood allows carbon dioxide to pass out, while oxygen passes in. Freshly infused with oxygen, the blood circles back through the heart for distribution to the rest of the body.
Within the respiratory zone, the air pressure changes as people breathe in and out to inflate and deflate the lungs. Careful control over pressure is also mediated with lubricant on the outside of the lungs which makes it easier to breathe. Lung elasticity and capacity can vary by age and level of health. As people age, their lungs may become less elastic, which makes it harder to breathe. Buildups of fluid in the chest can also contribute to compression in the respiratory zone, which limits the ability to inflate the lungs with fresh air.
The airway in general can be extremely sensitive to environmental pressures. Part of the purpose of the conducting zone is to trap particulate materials that could clog the respiratory zone and make it hard to breathe. These include smoke, pollen, dust, and other materials that may be present in the air. If these enter the lungs, they can cause irritation and inflammation, which leads to scarring over time. The scars decrease the patient’s ability to breathe comfortably.
Patients can develop chronic illnesses in the lungs as a result of occupational exposure to materials like asbestos fiber or coal dust. These may start with inflammation that leads to fibrosis, the development of tough scar tissue in the lungs. Chronic inflammation can also contribute to neoplasms, growths which may spread and turn cancerous. The respiratory zone is an area of particular medical concern because it is so critical for patient survival.