Long description

A drawing of a lung (pink) with a bronchus and branching bronchioles within the lung.

The ends of two of the bronchioles are shown in greatly expanded form. A terminal bronchiole is shown with a respiratory bronchiole, branching into two, leading from it. Around the ends of the respiratory bronchioles are alveolar sacs (looking like bunches of grapes), each comprising many spherical alveoli.

An alveolar sac is shown in expanded form. The sac is cut open to shown alveoli, also cut open, spherical units each with an alveolar pore.