Omposed of simple squamous epithelium. No exchange of gases occurs here. Composed of cuboidal cells. Secrete a fluid containing surfactant. The respiratory membrane is composed of fused basement membrane of the capillary walls and . Where the respiratory zone of the lungs begins. Terminates in alveoli.

Respiratory bronchioles

Explanation:

Bronchioles open into terminal bronchioles, which are thin-walled branches of the bronchioles further terminal bronchioles transition into respiratory bronchioles occurs

Respiratory bronchioles are lined by two types of epithelial cells: ciliated columnar cells and club cells( cuboidal cells)Walls of respiratory bronchioles are discontinuous, forming openings into alveolar ductsAlveolar ducts are conducting regions are lined by knob-like projections of cuboidal epithelium that cover small amounts of smooth muscleThese projections of cuboidal epithelium are often located on either side of the entrance into alveolar sacs, which branch from the “walls” of the alveolar ductsAlveolar sacs are indistinct segments that open into individual alveoli