The glands which are most immediately connected with digestion are very numerous small organs, situated in the mucous membrane of the alimentary canal, and the larger glands, such as the salivary glands, pancreas, and liver, whose ducts open on its inner surface.
The mouth is included between the lips and the throat, bounded by the lips, cheeks, tongue, and hard and soft palate. It communicates behind with the pharynx, and through the pharynx with the æsophagus. It is lined throughout with mucous membrane.
The mouth contains 32 teeth, 16 in the upper jaw and 16 in the lower jaw. The inferior maxillary bone, or lower jaw, is the only movable bone about the head. The teeth have for their functions biting, grinding, chewing, or triturating any hard food substance that may be introduced into the mouth.
The tongue is a muscular organ covered with mucous membrane. By its muscular structure it takes part in the process of mastication and deglutition, and in the articulation of speech, while its mucous membrane, with common and tactile sensibility, is the seat of the sense of taste.
The tonsils are two prominent bodies which occupy the recesses formed, one on each side of the fauces, between the anterior and posterior palatine arches and the pillars of the fauces.
The saliva, which is poured into the mouth and there mixed with the food during mastication, is secreted by three pairs of glands named from their respective situation parotid, submaxillary, and sublingual.
The parotid is the largest of three salivary glands. It lies on the side of the face, in front of the ear, and extends deeply into the space behind the ramus of the lower jaw. Its weight varies from 5 to 8 drachms. It has a duct called the parotid or Stenson’s duct. It is about 2½ inches long, and about a line and a half in thickness. Its orifice is opposite the crown of the second molar tooth of the upper jaw.
The submaxillary gland weighs about 2 to 2½ drachms, and is situated on the inner surface of the inferior maxillary. The duct is named Wharton’s, and is about 2 inches in length. Its orifice is found under the tongue.
The sublingual gland weighs about a drachm. It is situated on the floor of the mouth. The ducts are called the ducti Rivintiani. They are from 8 to 20 in number. They may be seen when the tip of the tongue is lifted up.
Saliva. Mixed saliva, as it appears in the mouth, is a thick, glairy, generally frothy, turbid fluid.