What are the parts of respiratory tree to which aleoli attached?

Alveoli are the tiny, balloon-like sacs in the lungs where gas exchange takes place. They are attached to the distal ends of the respiratory bronchioles, which are the smallest branches of the bronchial tree. The respiratory bronchioles lead into the alveolar ducts, which are short passages that connect to the alveoli. The alveoli are lined with capillaries, which are tiny blood vessels that allow oxygen and carbon dioxide to be exchanged between the air and the blood.