Bronchioles and alveoli (English)

On the right, a macroscopic view shows the branching of the bronchial tree. On the left, the microstructure of respiratory bronchioles, alveoli and associated neurovasculature are shown. Bronchioles arise from the intrasegmental bronchi, lack cartilage and may divide up to 20-25 times. The final nonrespiratory division of a bronchiole (i.e. sole function is gas conduction) is known a terminal bronchiole. They divide into respiratory bronchioles which open into alveolar sacs containing alveoli, via alveolar ducts. Externally, each alveolar sac is surrounded by a nest of blood capillaries supplied by small branches of the pulmonary and bronchial arteries.