Thin-walled air sacs extending from respiratory bronchioles
Cobweb of pulmonary capillaries
Macrophages
Surrounded by fine elastic fibers
Alveoli
Squamous epithelial cells
Type 1 alveolar cells
Cuboidal epithelial cells scattered amongst type 1 cells
Type 2 alveolar cells
Capillary, alveolar walls, and basement membrane
0.5-µm-thick blood air barrier
Respiratory Membrane
Site of gas exchange through simple diffusion
Respiratory Membrane
Secretes antimicrobial proteins for innate immunity
Secretes surfactant
Fluid containing a detergent-like substance that coats gas-exposed alveolar surfaces
Type 2 alveolar cells
Connects adjacent alveoli to allow air pressure throughout the lung to be equalized
Provides alternate routes to any collapsed alveoli
Alveolar Pores
Alveolar walls
Type 1 alveolar cells
_____________ decreases the ___________ of ______ molecules
decreases the amount of _________ _________ in the alveolar fluid discouraging ________ _________
surfactant
cohesiveness
water
surface tension
alveolar collapse