Lung -- organ in which bronchi become highly branched and in which respiratory exchange occurs.

Study the functional organization of lung tissue as shown, noting especially the extra- and intrapulmonary airways and the intrapulmonary blood circulation around the alveoli.

Examine an H&E-stained section of the lung.

Indicate the function of the cells that air contacts as it moves deeper and deeper into the lung?

What is the major histological difference between the conducting and the respiratory portions of the airway?

 

Clinical note: Asthma involves hyperirritability of the respiratory passages, expressed as contraction of the bronchial smooth muscle, edema of the mucosa, and increased mucus secretion. It may be transient, following an upper respiratory tract infection, but more commonly the sensitization has an immunological basis and the symptoms are episodic. Re-exposure to an airborne antigen such as pollen causes release of histamine from mast cells and eosinophils, precipitating immediate bronchioconstriction and labored breathing. Various drugs are helpful in minimizing the severity of the attacks.

Pneumocytes and macrophages.