134 ANATOMY AND PHYSIOLOGY 



Salivary glands. The digestive fluid of the mouth is called 

 saliva. It is secreted by the salivary glands, three in number on 

 each side the parotid, submaxillary, and sublingual (Fig. 101). 



The parotid gland is situated in front of and below the ear, 

 and has a duct about two inches long (Stenson's duct) which runs 

 forward to open into the mouth opposite the second molar tooth 

 of the upper jaw, piercing the buccinator muscle. It secretes an 

 abundant watery fluid. 



The surface line of Stenson's duct is drawn from the lobe of the ear to the 

 middle of the upper lip. 



The submaxillary gland lies under the angle of the jaw, open- 

 ing into the floor of the mouth close to the f renum, by Wharton y s 

 duct. It secretes a thicker fluid than the parotid gland. 



The sublingual gland lies in the (anterior) floor of the mouth 

 and opens under the tongue near the frenum, by several small 

 ducts. This also secretes a thicker fluid. 



The fluid which is constantly present in the mouth and com- 

 monly called saliva, is a mixture of the secretion of the salivary 

 glands and the mucous glands of the mouth. 



The reaction of the saliva is alkaline. The enzymes or ferments 

 of saliva are ptyalin and maltase. The average daily quantity 

 of mixed saliva is 1400 gm. 



THE PHARYNX 



The pharynx, or throat, receives the food from the mouth. It 

 occupies a space in front of the spinal column from the base of the 

 skull to the fifth cervical vertebra, its roof being formed by the 

 body of the sphenoid bone, joined to the occipital. The walls of the 

 pharynx consist of three pairs of muscles called the constrictors 

 upper, middle, and lower, strengthened by a fibrous layer and 

 lined with mucous membrane. 



The illustration shows that the constrictors are flat muscles attached at 

 the sides to the structures in front of the pharynx. Thus, from above down- 

 , ward, their origin is on the pterygoid process, a special ligament, the mandible, 

 side of the tongue, hyoid bone, thyroid and cricoid cartilages. The fibers all 

 join a fibrous line, or raphe, at the back, which is suspended from the base 

 of the occipital bone. This is their insertion. 



By due contraction of these muscles the food is grasped and 

 pressed downward into the esophagus. They are composed of 

 striated or voluntary muscle fibers. 



