Trachea front and sides of the trachea to protect and maintain the airway. In front of the rings lies connective tissue and skin. Several other structures pass or sit over it; the jugular arch, which joins the two anterior jugular veins, sits in front of the upper part of the trachea. The sternohyoid and sternothyroid muscles stretch along its length, and the thyroid gland sits below this; with the isthmus of the gland overlying the second to fourth rings. The first tracheal ring is broader than the rest, and often divided at one end; it is connected by the cricotracheal ligament
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.