Smoke inhalation injury, bronchial alveolar wash, horse

Photomicrograph of bronchial alveolar wash from a horse, showing carbon particles associated with alveolar macrophages due to smoke inhalation injury. Chemical injury continues as long as chemical-covered carbon particles remain attached to the airway mucosa; the size of the particles determines where damage will occur within the respiratory tree: larger particles (a few micrometers in diameter) become deposited in the upper respiratory tract, whereas ultrafine particles (< 0.1 mcm) diffuse into the alveoli. Wright stain.