1) Respiratory bronchioles
2) Alveolar ducts ("stem" or "hallway")
- 3) Alveolar sacs ("bunches of grapes")
- • terminal clusters of alveoli
- • atrium = opening into the sac
- 4) Alveoli
- • most of lung volume
• simple squamous cells (“type-I cells”)
• surfactant secreting simple cuboidal cells(“type-II cells”)• alveolar macrophages (“dust cells”)
• alveoli + pulmonary capillaries (squamous) =“Respiratory membrane” or “Air-blood barrier”
• Alveolar pores = communication between alveoli