Trachea are generally highly elastic but they may calcify with age. The trachealis muscle connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen of the trachea to increase the rate of air flow. The esophagus lies posteriorly to the trachea, adjoining along the tracheoesophageal stripe. Circular horizontal bands of fibrous tissue called the annular ligaments of trachea join the tracheal rings together. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus. A flap-like epiglottis closes the opening to the larynx during swallowing
Traditional Chinese medicines derived from the human body parts of the human body should be used as drugs, such as bone, flesh, and gall. This is really very rude and inhuman. In the present category, all parts of the human body that have been used as drugs are recorded. The use of drugs from the human body that is not contrary to morality is recorded in detail. Those drugs that are cruel or foul [慘忍邪穢] are not recorded in detail. But all of them are listed in this category. (tr. Luo 2003: 4133) Li does not give prescriptions for 12 of the 35 human drugs, which he considered