Part 16 (1/2)

235-258. _Give the anatomy of the digestive organs._ 235. Name them.

236. Describe the mouth.

MOUTH is an irregular cavity, which contains the instruments of mastication and the organs of taste. It is bounded in front by the lips; on each side by the internal surface of the cheeks; above, by the _hard palate_ (roof of the mouth) and teeth of the upper jaw; below, by the tongue and teeth of the lower jaw; behind, it is continuous with the pharynx, but is separated from it by a kind of movable curtain, called the _soft palate_. This may be elevated or depressed, so as to close the pa.s.sage or leave it free.

237. The SALIVARY GLANDS are six in number; three on each side of the jaw. They are called the _pa-rotid_, the _sub-maxil-la-ry_ and the _sub-lingual_.

[Ill.u.s.tration: Fig. 58. A view of the salivary glands in their proper situations. 1, The parotid gland. 2, Its duct. 3, The submaxillary gland.

4, Its duct. 5, The sublingual gland, brought to view by the removal of a section of the lower jaw.]

238. The PAROTID GLAND, the largest, is situated in front of the external ear, and behind the angle of the jaw. A duct (Steno's) from this gland opens into the mouth, opposite the second molar tooth of the upper jaw.

237. How many glands about the mouth? Give their names. What does fig.

58 represent? 238. Describe the parotid gland.

239. The SUBMAXILLARY GLAND is situated within the lower jaw, anterior to its angle. Its excretory duct (Wharton's) opens into the mouth by the side of the _frnum lingu_, (bridle of the tongue.)

240. The _SUBLINGUAL GLAND_ is elongated and flattened, and situated beneath the mucous membrane of the floor of the mouth, on each side of the frnum lingu. It has seven or eight small ducts, which open into the mouth by the side of the bridle of the tongue.

_Observation._ In the ”mumps,” the parotid gland is diseased. The swelling under the tongue called the ”frog” is a disease of the sublingual gland.

[Ill.u.s.tration: Fig. 59. A side view of the face, oesophagus, and trachea.

1, The trachea (wind pipe.) 2, The larynx. 3, The oesophagus. 4, 4, 4, The muscles of the upper portion of the oesophagus forming the pharynx.

5, The muscle of the cheek. 6, The muscle that surrounds, the mouth. 7, The muscle that forms the floor of the mouth.]

239. The submaxillary. 240. The sublingual. What observation respecting these glands? What does fig. 59 represent?

241. The PHARYNX is a membranous sac, situated upon the upper portion of the spinal column. It extends from the base of the skull to the top of the _trache-a_, (windpipe,) and is continuous with the oesophagus.

From the pharynx are four pa.s.sages; one opens upward and forward to the nose, the second leads forward to the mouth, the third downward to the trachea and lungs, the fourth downward and backward to the stomach.

242. The OESOPHAGUS is a large membranous tube that extends behind the trachea, the heart, and lungs, pierces the diaphragm, and terminates in the stomach. It is composed of two membranes--an internal, or mucous, and a muscular coat. The latter is composed of two sets of fibres; one extends lengthwise, the other is arranged in circular bands.

243. The STOMACH is situated in the left side of the abdomen, immediately below and in contact with the diaphragm. It has two openings; one connected with the oesophagus, called the _cardi-ac_ orifice; the other connected with the upper portion of the small intestine, called the _py-loric_ orifice. It is composed of three coats, or membranes. The exterior or serous coat is very tough and strong, and invests every part of this important organ. The middle, or muscular coat is composed of two layers of muscular fibres, one set of which is arranged longitudinally, the other circularly. The interior coat is called the mucous, and is arranged in _rug_, (folds.) The stomach is provided with a mult.i.tude of small glands, in which is secreted the gastric fluid.

_Ill.u.s.tration._ The three coats of the stomach anatomically resemble tripe, which is a preparation of the largest stomach of the cow or ox.

The outer coat is smooth and highly polished. The middle coat is composed of minute threads, which are arranged in two layers. The fibres of these layers cross each other. The inner coat is soft, and presents many folds, usually named ”the honey-comb.”