The Digestive Organs.
THE alimentary organs are the mouth, the teeth, the salivary glands, the pharynx, the gullet (cesophagus), stomach, bowels (intestines), chyle vessels (lacteals), thoracic duct, liver and sweetbread (pancreas). The preparatory process of digestion, the mastication'of food, takes place in the mouth, where the food is mixed with saliva, a secretion of the salivary glands. Of these glands there are six, three on each side.
The Parotid Gland lies in front of the external ear. It has a duct opening into the mouth opposite the second molar tooth of the upper jaw. This is the gland that swells in the disease called mumps. Hence the disease is also called parotitis. The Submaxillary Gland is inclosed within the lower jaw, in front of its angle. Its duct opens into the mouth by the side of the bridle of the tongue (froonum linguee). On each side of this string or bridle, and under the mucous membrane of the floor of the mouth, lies the sublingual gland, which pours its saliva into the mouth, through seven or eight small ducts.
A disease called the frog consists in the swelling of this gland. Mg. 28: 1, the parotid gland; 2, its duct; 3, the sub maxillary; 4, its duct 5, the sublingual. The Pharynx is a continuation of the mouth, and is the cavity just below the soft palate. The two passages going to the nose (posterior nares), the one going to the stomach (cesophagus), and the one going to the lungs (larynx and trachea; all meet in this cavity. In Fig. 29: 1, is the trachea; 2, the larynx; 3, the esophagus; 4, 4, 4, muscles of pharynx; 5, muscles of the cheek; 6, the musclewhich surrounds the mouth; 7, the muscle forming the floor of the mouth.
The Gullet or esophagus is a long tube, descending behind the windpipe, the lungs, and the heart, through the diaphragm into the stomach. It is composed of two membranes laid together, like two pieces of cloth. The inner one is mucous, the outer muscular. The two sets of fibers composing the muscular coat are arranged circularly and longitudinally (Fig. 25). The Stomach lies in the upper part of the belly, to the left, and directly under the diaphragm. It has an upper opening, where the stomachpipe enters it, called the Cardiac orfice. This is the larger end of the the stomach and lies on the left side; the smaller end connects with the the upper bowel,at which point it has an opening called the pyloric orfice. In addition to mucous and muscular coats, similar to those which compose the esophogus, the stomach has still another over both, a serous coat, very strong and tough, to give this working organ additional endurance. Within , it has many glands to secrete gastric juice.
The Intestines, or alimentary tube,or bowels are devided in the small and large intestines. The small intestines has a length of aboiut twenty five feet, and is devided into three parts, The duodenum, the jejunum, and the ileum. of these three devisions, the duodenum is the largest and is about a foot in length. It begins at the pyloric orifice of the stomach, and passes backward to the under surface of the liver, whence it drops down perpendicularly in front of the right kidney, and passes across the belly behind the colon, and ends in, the jejunum.
The Jejunum continues the above, and terminates in the ileum. The Ileum is a continuation of the jejunum, and opens, at an obtuse angle, near the haunch bone, into the colon. A valve is located here, to prevent the backward passage of substances from the colon into the ileum. At this point the large intestines begin, and here is situated the c6ecum, a blind pouch, or culdesac, attached to which is the appen, dix vermiformis, a wormshaped tube, of the size of a goosequill, and from one to six inches long.
The Colon, or large intestine, is divided into the ascending colon, the transverse colon, and the descending colon. The Ascending Colon rises from the right haunchbone to the under surface of the liver, whence it bends inward, and crosses the upper part of the belly, below the liver and stomach, to the left side. This portion which crosses over is the transverse colon. From this point, on the left side, it turns down to the left haunch, and has the name of the descending colon. Here it makes a curve like the letter S, which is called the sigmoid flexure. The Rectum is the lower portion of the large intestine, terminating at the anus.
The Lacteals are small vessels which begin in the villi, upon the mucous membrane of the small bowels. From here they pass between membranes of the me8entery to small glands, from which larger vessels run to another collection of glands; and after passing, for a space, from one collection of glands to another, at each stage of their progress increased in size and diminished in number, the lacteals pour their contents into the thoracic duct.
This having passed up through the diaphragm, out of the belly, makes a
sudden turn downward and forward, and empties its burden into a large
vein which ends in the right heart. Fig. 30 : 1, is the bowel; 2, 3, 4,
the mesenteric glands through which the lacteals pass; 5, the thoracic
duct; 7, the spinal colunm; 8, the diaphragm. By the help of a
magnifying glass, an infinite number of these small vessels may be seen
starting from the rough, shaggy internal coat of the bowel.
The mesentery is a thick sheet of membrane, formed of several folds of the peritoneum, and spread out from the vertebrae like a fan. The bowels are attached to its edge, and are held by it in their place, and at the same time have free motion. Between its layers are a great number of glands, which sometimes become diseased and swollen in childhood, and prevent the chyle from passing along to the thoracic duct. Thus affected, children are not nourished, and waste away with a disease sometimes called mesenteric consumption.
The Liver is a large gland, lying under the short ribs on the right side, below the diaphragm. It is convex on the upper surface and
concave on the under, and is composed of several lobes. Its office is to secrete bile. It weighs about four pounds, being the largest organ in the body. Fig. 31 represents the liver: 1, being the right lobe; 2,leftlobe; 3,4, smaller lobes; 10, gallbladder; 17, the notch into which the spinal column is fitted. The GallBladder lies on the under side of the liver, and receives, it is supposed, the surplus bile, which is reserved for special occasions. It opens into the gall duct, which carries the bile along, and pours it into the duodenum. The Pancreas, Fig. 32, is a long, flat gland,
something like the salivary glands. It lies transversely across the back wall of the abdomen, behind the stomach. It secretes a colorless, alkaline fluid called the pan, creatic juice, the office of which is to emulsify the different classes of food, so that the lacteals can absorb it. This fluid is carried by a duct and poured into the duodenum just where the bile duct enters.
The spleen has an oblong, flattened form. It lies on the left side just under the pancreas. It is suppose to be a reservoir for holding the surplus blood of the liver. It was thought by the ancients to be the seat of melencholy. the blood in passing through it loses portion of its red globules.
The Omentum or caul is a doubling and extension of the peritoneum. It is a kind of fatty body, which lies upon the surface of the bowels and is attached to the stomach. Its use seems to be to lubricate the bowels, and especially to protect and keep them warm. Hence it is often called the apron.
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