Page:First course in biology (IA firstcourseinbio00bailrich).pdf/540

 , showing palate and tonsils.

, P; with trachea, TA; thyroid gland, th; larynx, L; and hyoid bone, H.

two tubes open from the pharynx. One is the trachea (trā'kea) or windpipe, the other is the esophagus or gullet. At the top of the trachea is the cartilaginous larynx, or voice box. If the finger is placed upon the larynx or Adam's apple, it is plainly felt to move up and down when swallowing. The opening into the larynx is provided with a lid of cartilage, the epiglottis. Inside the larynx, the vocal cords are stretched from front to back. Just below the larynx comes the trachea proper, which is a tube about three fourths of an inch in diameter and about four inches long (Fig. 69). It consists of hoops of cartilage (Fig. 69) which are not complete circles, but are shaped somewhat like the letter C, being completed at the rear by involuntary muscular tissue, whose function