The meridian begins at the outer nail corner of the index finger, travels up the radial border of the hand, crosses the anatomical snuffbox between the two thumb tendons, then follows the lateral aspect of the forearm and arm to the shoulder. It reaches the seventh cervical vertebra, descends to the clavicle and penetrates deeply to the lung and large intestine. A superficial branch rises up the neck, crosses the cheek, reaches the lower teeth, curves around the upper lip and ends beside the opposite nostril.
The Large Intestine receives the residue of digestion from the Small Intestine, reabsorbs its fluids and eliminates the rest. This function of transmission and elimination is inseparable from that of the Lung: a Lung that fails to send Qi downwards often results in constipation. Along its pathway the meridian treats pain in the arm and shoulder, and disorders of the face, nose, teeth and throat. It also plays a recognised role in releasing the exterior during wind invasion.