Bronchioles are tiny airways that carry oxygen to alveoli, or air sacs, in the lungs and help stabilize breathing in the respiratory system, according to About.com. Bronchioles are lined with smooth muscular walls that c... More »

Terminal bronchioles are the air passages into the lungs. They branch into respiratory bronchioles and secrete a nonsticky surfactant to maintain the airway. Surfactant is a proteinaceous compound that maintains the airw... More »

Bronchi are the transition structures that air travels through between the right and left main bronchus, and the very small bronchioles. The air first travels from the mouth or nose through the larynx and trachea, and th... More »

Pulmonary alveoli are the tiny sacs inside the lungs that fill with air with each breath and facilitate the exchange of gas with the blood. According to HowStuffWorks, the oxygen concentration in the alveoli is high, rel... More »

The respiratory system's structured pathways enable breathing by carrying oxygen to the lungs and filtering out harmful substances, explains WebMD. Respiratory organs also expel carbon dioxide from the body and transport... More »

The respiratory system draws in fresh air from the environment, exchanges oxygen for waste gases in the lungs and expels the spent air back into the environment before taking another breath. The oxygen is then circulated... More »

www.reference.com Science Human Anatomy Organs

The primary function of the respiratory system is to remove oxygen from the air and exchange it with carbon dioxide in the human lugs. The respiratory system draws air into the lungs, where it enters the alveoli. The alv... More »