A morphometric study of bronchial and bronchiolar walls in children.

The components of the major bronchi were quantitated in 17 children and 5 adults, and the amount of muscle was quantitated in the bronchioles of the same subjects. Mucous glands formed a larger proportion of the walls of major bronchi in normal children than in normal adults. In children with fibrocystic disease and bronchiolitis, the proportion of mucous glands in bronchi was greater than that in adults with bronchitis. In both children and adults, the proportion of muscle was larger in the small airways than in major airways. The proportion of muscle in the major bronchi was the same in children and adults, but the proportion of muscle in the small airways was smaller in children than in adults.