Part 16 (2/2)

241. Describe the pharynx and the pa.s.sages leading from it. 242. Give the structure of the oesophagus. 243. Where is the stomach situated?

How many coats has it? Describe them. What article prepared for food does the stomach resemble?

[Ill.u.s.tration: Fig. 60. The inner surface of the stomach and duodenum. 1, The lower portion of the oesophagus. 2, The opening through which the food is pa.s.sed into the stomach. 8, The stomach. 9, The opening through which the food pa.s.ses out of the stomach into the duodenum, or upper portion of the small intestine. 10, 11, 14, The duodenum 12, 13, Ducts through which the bile and pancreatic fluid pa.s.s into it. _a_, _b_, _c_, The three coats of the stomach.]

244. The INTESTINES, or alimentary ca.n.a.l, are divided into two parts--the _small_ and _large_. The small intestine is about twenty-five feet in length, and is divided into three portions, namely, the _Du-o-denum_, the _Je-junum_, and the _Ile-um_. The large intestine is about five feet in length, and is divided into three parts, namely, the _Cc.u.m_, the _Colon_, and the _r.e.c.t.u.m_.

(Appendix D.)

245. The DUODENUM is somewhat larger than the rest of the small intestine, and has received its name from being in length about the breadth of twelve fingers. It commences at the pylorus, and ascends obliquely backward to the under surface of the liver. It then descends perpendicularly in front of the right kidney, and pa.s.ses transversely across the lower portion of the spinal column, behind the colon, and terminates in the jejunum. The ducts from the liver and pancreas open into the perpendicular portion, about six inches from the stomach.

244. Explain fig. 60. What is the length of the small intestine, and how is it divided? What is the length of the large intestine? Give its divisions. 245. Describe the duodenum.

246. The JEJUNUM is continuous with the duodenum. It is thicker than the rest of the small intestine, and has a pinkish tinge.

247. The ILEUM is smaller, and thinner in texture, and somewhat paler, than the jejunum. There is no mark to distinguish the termination of the one or the commencement of the other. The ileum terminates near the right haunch-bone, by a valvular opening into the colon at an obtuse angle. This arrangement prevents the pa.s.sing of substances from the colon into the ileum. The jejunum and ileum are surrounded above and at the sides by the colon.

248. The small intestine, like the stomach, has three coats. The inner, or mucous coat is thrown into folds, or valves. In consequence of this valvular arrangement, the mucous membrane is more extensive than the other tissues, and gives a greater extent of surface with which the aliment comes in contact. There are imbedded under this membrane an immense number of minute glands, and it has a great number of piles, like those upon velvet. For this reason, this membrane is sometimes called the _villous_ coat.

249. The Cc.u.m is the blind pouch, or cul-de-sac, at the commencement of the large intestine. Attached to its extremity is the _ap-pendix verm-i-formis_, (a long, worm-shaped tube.) It is from one to six inches in length, and of the size of a goose-quill.

What important ducts open into it? 246. Describe the jejunum. 247. The ileum. 248. What is said of the coats of the intestines? Why is the mucous membrane sometimes called the villous coat? 249. Describe the cc.u.m.

250. The COLON is divided into three parts--the _ascending_, _transverse_, and _descending_. The ascending colon pa.s.ses upward from the right haunch-bone to the under surface of the liver. It then bends inward, and crosses the upper part of the abdomen, below the liver and stomach, to the left side under the name of the transverse colon. At the left side, it turns, and descends to the left haunch-bone, and is called the descending colon. Here it makes a peculiar curve upon itself, which is called the _sigmoid flexure_.

[Ill.u.s.tration: Fig. 61. 1, 1, The duodenum. 2, 2, The small intestine. 3, The junction of the small intestine with the colon. 4, The appendix vermiformis. 5, The cc.u.m. 6, The ascending colon. 7, The transverse colon. 8, The descending colon. 9, The sigmoid flexure of the colon. 10, The r.e.c.t.u.m.]

250. Describe the course of the divisions of the colon. Explain fig.

61.

251. The r.e.c.t.u.m is the termination of the large intestine. The large intestine has three coats, like the stomach and small intestine. The longitudinal fibres of the muscular coat are collected into three bands. These bands are nearly one half shorter than the intestine, and give it a sacculated appearance, which is characteristic of the cc.u.m and colon.

252. The LACTEALS are minute vessels, which commence in the villi, upon the mucous surface of the small intestine. From the intestine they pa.s.s between the membranes of the _mesen-ter-y_ to small glands, which they enter. The first range of glands collects many small vessels, and transmits a few larger branches to a second range of glands; and, finally, after pa.s.sing through several successive ranges of these glandular bodies, the lacteals, diminished in number and increased in size, proceed to the enlarged portion of the thoracic duct, into which they open. They are most numerous in the upper portion of the small intestine.

253. The THORACIC DUCT commences in the abdomen, by a considerable dilatation, which is situated in front of the lower portion of the spinal column. From this point, it pa.s.ses through the diaphragm, and ascends to the lower part of the neck. In its ascent, it lies anterior to the spine, and by the side of the aorta and oesophagus. At the lower part of the neck, it makes a sudden turn downward and forward, and terminates by opening into a large vein which pa.s.ses to the heart.

The thoracic duct is equal in diameter to a goose-quill, and, at its termination, is provided with a pair of semilunar valves, which prevent the admission of venous blood into its cylinder.

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