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 being are no more used medically, it seems rude to list them as drugs." Note the medical terms "dystocia" "A slow or difficult labor or delivery" and "stranguria" (i.e., "strangury" "A painful, frequent need to urinate, when the bladder is largely empty or with little urine production"). Reflecting the well-known Confucianist inhibition against mutilating one's body (Cooper & Sivin 1973: 212), Li Shizhen's preface to chapter 52 ethically condemns the use of some human drugs. The human is a different species from all the other organisms used as sources of drugs. In later times, Taoist alchemists [方伎之士] considered that many