The meridian originates in the Middle Burner, descends towards the large intestine, then rises through the diaphragm to the lung. It surfaces below the clavicle at the first point, runs along the antero-lateral aspect of the arm, follows the radial border of the forearm, crosses the wrist at the radial artery, travels over the thenar eminence and ends at the outer nail corner of the thumb. A secondary branch leaves at the wrist and reaches the index finger, where it connects with the Large Intestine meridian.
The Lung governs Qi and respiration: it receives clear air and, together with the Spleen, produces acquired energy. It diffuses Qi and fluids towards the skin and body hair, and directs them downwards, which is why it regulates the water passages. It commands defensive Qi, the first barrier against wind and cold. It opens into the nose and manifests in the voice. Its corresponding emotion is sadness.