This four-stage cross section of the bronchus demonstrates the tissue changes occurring in asthma and chronic bronchitis. The four stages include: normal bronchus, hypersecretion of the mucous gland, swelling with lymphoid aggregations, and smooth-muscle spasm. The model includes: cartilage, mucous glands and plug, spiraling smooth muscles, and the fibroelastic connective tissue and epithelial layers of the bronchus. All stages rotate on a hinge pin. Model size of each replica: 3-3/4" x 1-1/2" dia. Grade 6 and up.