Respiratory tractOnline version PAGE 55 by Secundaria Digital 1 Group 1 2 Group 2 3 Group 3 4 Group 4 5 Group 5 6 Group 6 Nasal cavity Where air enters the body. In the first section, the internal wall has several capillaries, which warm up the air because they carry blood. The presence of nooks and crannies in this section of the respiratory tract increases the lenght of the journey air goes within the body, making it warmer. In this section, air is purified and humidified. Pharynx This area is common to the respiratory and digestive tracts. Foods continue their journey into the esophagus, while air passes into the larynx. On the sides of this airway there are tonsils, which produce white blood cells. Larynx Entry to this area is regulated by a fibrous structure known as the epiglottis, which closes when food is being ingested to prevent the organism from choking or suffocating. The walls of this tube are formed of cartilage that continually keeps it open. Trachea It's about 12 cm long. It has open cartilage rings at its back. There's mucous present in the interior of this section that traps foreign particles in the air. In this part of the respiratory tract there are certain cells with vibrating filaments know as cilia. Bronchi They are two airways. Each tube enters a different lung. They branch into progressively smaller ducts. Bronchioles They don't have cartilage rings. They end in tiny sacts, called pulmonary alveoli.