DIGESTIVE SYSTEM 317 



tongue). The ducts from these glands open in the 

 floor of the mouth just below and back of the lower 

 incisor teeth. 



Throat or pharynx. This is a small cone-shaped 

 cavity just back of the mouth cavity. On each side 

 of the throat there is an almond-shaped gland, the tons-il. 

 There are seven openings in the throat: two at the 

 top open into the nasal cavity, one into the mouth, one 

 into the esophagus, one into the wind pipe, and one into 

 each ear. The tubes leading to the ears are known as 

 the Eustachian tubes. The wind pipe lies in front of 

 (or ventral to) the gullet. At the top of the wind pipe 

 is the voice box. This can be closed by a small trap 

 door called the epiglottis. 



Esophagus. The esophagus is a narrow tube about 

 nine inches long leading from the throat to the stomach. 

 Just before it reaches the stomach it passes through a 

 sheet of muscle and connective tissue known as the 

 diaphragm. This muscular partition divides the body 

 into an upper portion, the thorax, and a lower portion, 

 the abdomen. 



Stomach. The stomach lies in the middle of the body 

 just below the diaphragm. It is a muscular organ, 

 more or less pear-shaped with the larger end lying toward 

 the left side. When moderately filled, it holds about 

 three pints. The small end of the stomach is con- 

 tinuous with the intestine. The opening into the small 

 intestine is controlled by a ring of muscle. The con- 

 traction of this muscle closes the opening and prevents 



