The human respiratory system consists of a conducting part and a respiratory or exchange part. The conducting part includes the external nostrils,nasal passage,pharynx,larynx,trachea,bronchi,and bronchioles. The exchange part consists of the alveoli and their ducts. The lungs are situated in the thoracic chamber,which is anatomically an air-tight chamber. The thoracic chamber is formed dorsally by the vertebral column,ventrally by the sternum,laterally by the ribs,and on the lower side by the dome-shaped diaphragm. The lungs are covered by a double-layered pleura,with pleural fluid between them to reduce friction on the lung surface. The diagram shows the structural organization of these components.