Trachea annular ligaments of trachea. The epiglottis closes the opening to the larynx during swallowing. The trachea develops in the second month of development. It is lined with an epithelium that has goblet cells which produce protective mucins (see "Respiratory epithelium"). An inflammatory condition, also involving the larynx and bronchi, called croup can result in a barking cough. A tracheotomy is often performed for ventilation in surgical operations where needed. Intubation is also carried out for the same reason by the inserting of a tube into the trachea. From 2008, operations have experimentally transplanted a windpipe grown by stem cells, and
Traditional Chinese medicines derived from the human body story, it would seem that those 'who go down to the silkworm room' [who are administratively sentenced to castration] should not be ignorant of this method, so I append it here." In some "Bencao gangmu" contexts concerning human drugs, Li Shizhen would accept the traditional theory but deny the contemporary practice. Under the human breath or "qi" section (52.23, tr. Luo 2003: 4176), Li says a "very effective" method for treating an elderly person who is suffering from cold and deficiency in the lower body is to have a boy or girl blow air through a cloth into the navel.