The main function of the respiratory system is the transferring of gases between the air and the blood.

The system is comprised of tubes and highly branched channels which terminate in dead-end sacs where gas transfer occurs. Air brought into the body is first conditioned and filtered in the first part of the respiratory system, the conducting portion (nasal cavity to bronchioles). The second part of the system, the respiratory portion, consists of the respiratory bronchioles and alveoli are involved with gas exchange.

Learning Objectives:

• Understand the structure and functions of the conducting portion of the respiratory system.
• Recognize and describe respiratory epithelium and the functional significance of its structural features.
• Understand the structures of the larynx, trachea, and bronchial trees.
• Understand the structure and functions of respiratory bronchioles, alveolar ducts, and alveoli.
• Recognize and understand the functions of type I and type II pneumocytes and alveolar macrophages.
• Recognize and understand the layers in the barrier between blood in alveolar capillaries and air in the alveoli.
• The basic anatomy of the upper respiratory tract is shown in the diagram on the next page.

Let's start at the top with the nasal cavity.