Mucosa

“ Figure 46 shows portions of typical glands [178] from the mucosa of the middle region of the stomach, the posterior border of the large stomach cavity; A is a longitudinal section through two ducts where they open to the surface; B is a similar section through the body of a gland below the region of the duct; C is a transsection through the bottom or fundus of a gland; all are drawn with a camera under the same magnification. ”

“ The submucosa, sm, is of considerable thickness. [169] It is composed of a fairly dense mass of connective tissue, mainly elastic fibers, through which are scattered small blood-vessels, bv, and small dark areas, mb, that are apparently longitudinal bundles of involuntary muscle fibers. These few and scattered fibers probably represent the muscularis mucosa that is so well developed in the posterior region of the œsophagus. ”

“ But the inside of the body also has a skin, as have all its organs. The interior of the head, the throat, the gullet, the lungs, the stomach, and all the intestines, are lined with a skin. This is called the mucous membrane, because it is constantly secreting from the blood a slimy substance called mucus. When it accumulates in the lungs, it is called phlegm. This inner skin also has nerves, blood-vessels, and lymphatics. ”

“ First, other congeries of glands occupy but a particular part of the system, or constitute a particular organ, as the liver, or kidneys; but those glands, which secrete the mucus, and perspirable matter, which are called capillaries, are of very great extent; they receive the blood from the arteries, separate from it the mucus, which lines every cell, and covers every cavity of body; and the perspirable matter, which softens and lubricates the whole surface of the skin, and the more extensive surface of the air-vessels, which compose the lungs. ”

“ In chronic inflammation of the rectum and colon there is more or less discharge of mucous, and in some cases of membranous, desquamation, with yellow or bloody mucus. The shreds, cords or complete tubular casts are discharged constantly or at varying intervals. The quantity and character often alarm the sufferer. The discharge is nothing less than a thick, tenacious mucus that had formed a thin coating on the inflamed mucous membrane, and become exfoliated in casts or thin shreds—the result of many years of morbid intestinal exaggerated action. ”

“ The skin is not, as it should be, held fast by the connective tissue, but lies loose over the cavity; and a similar pathological condition exists under the mucous membrane of the anus, rectum, and sigmoid flexure, which circum­stance might lead one, in some instances, to conclude that there was almost an entire separation of the mucous membrane from the areolar tissue, by the ridges, folds, large, pouched, prolapsed, sacculated regions of mucous membrane that has the appearance of having been simply carelessly laid over the muscular structure of the organs. ”

“ OF THE EXTERIOR ORGANIZATION OF MUCOUS MEMBRANES.
8. Every mucous membrane presents two surfaces; the one adhering to the adjacent organs; the other free, beset with villosities, and always moist with a mucous fluid: each of them deserves a particular attention.
9. The adherent surface is attached to muscles almost throughout its extent. The mouth, the pharynx, the whole of the alimentary canal, the bladder, the vagina, the uterus, and part of the urethra, &c. present a muscular bed, embracing [10] the exterior of their mucous coat. ”

“ The food is masticated by a very complicated system of jaws and teeth, and after it has been mixed with a secretion, which is poured into the mouth by salivary glands, it passes through a long muscular œsophagus into the stomach, where it is acted upon by fluids furnished by a liver and other glands, before it passes into the long, convoluted intestine, where the nutritive portions are absorbed into the blood, while the waste products are discharged from the body through the anus. ”

“ The external or serous coat is derived from the peritoneum. There are three kinds of muscular fibers—longitudinal, circular, and oblique, and the internal mucous lining is a rather thicker, soft, smooth, pulpy membrane, lying in ridges or rugæ, and containing a large number of glands—tubular or gastric glands, and another variety of gland called peptic, besides others.
While the stomach contains no food, and is inactive, no gastric fluid is secreted; and mucus, which is either neutral or slightly alkaline, covers its surface. ”

“ The fluid or bile thus secreted, when in a healthy state, and not in undue proportion, stimulates the mucous membrane, and increases the peristaltic motion of the intestines, excites the secretion of that mucus requisite to preserve these parts in a healthy state, hastens the process of separating the nutritious from the innutritious parts of the food, and facilitates the escape of the fæcal matters. It also acts chemically upon the various substances which are devoured by the animal, and is the chief agent in neutralizing the acidity which some of these would otherwise create. ”

“ Remark the fact, that none of the mucous fluids enter into the circulation, but are thrown out externally; that of the bladder, ureters, and urethra, with the urine; that of the vesiculæ seminales [49] and of the vassa defferentia with the semen; that of the nostrils by the action of blowing the nose; that of the mouth partly by evaporation, and partly by the anus with the excrements; that of the bronchi by the pulmonary exhalation, which is effected principally by the solution of this mucous fluid in the air of respiration ”

“ The muscular coat of the small intestine is made up of two distinct layers—the inner layer consisting of circular fibers and the outer of longitudinal fibers. These muscles keep the food materials mixed with the juices of the small intestine, but their main purpose is to force the materials undergoing digestion through this long and much-coiled tube.
The outer, or serous, coat of the small intestine, like that of the stomach, is an extension from the general lining of the abdominal cavity, or peritoneum. ”

“ Preternatural thickening of the membrane is often of very considerable extent: deposition of matter beneath it appears to be confined to the situations of the mucous glands. These glands are found in all states and stages of disease from the least to the greatest enlargement, and from the mere abrasion of their surface to the entire ulceration of their substance. Perhaps one of the glandulæ solitariæ enlarged and covered with inflamed mucous membrane may constitute the only morbid appearance discernible in the intestine ”

“ Microscopical examination of the desquamated intestinal membrane and mucus from a man forty years of age, revealed the following products: crystals, mostly complete; incomplete phosphates, very numerous; mucous shreds in abundance; fat globules and granules, numerous; anal epithelia; red blood globules, few; connective tissue, scanty; pus corpuscles, very few; margaric acid and detritus (substances resulting from the destruction or wearing away of the part) ; undigested material, mostly cellulose; leptothrix threads, micrococci; and the bacillus coli communis. ”

“ The mucous membrane lining the alimentary tract is the part most subject to pathological alterations, and in this connexion it should be remembered that this membrane differs both in structure and functions throughout the tract. Chiefly protective from the mouth to the cardia, it is secretory and absorbent in the stomach and bowel; while the glandular cells forming part of it secrete both acid and alkaline fluids, several ferments or mucus. Over the dorsum of the tongue its modified cells subserve the sense of taste. ”

“ There are, however, scattered throughout the skin, and also throughout the lining of the digestive tract, a number of specially modified epithelial cells, which are no doubt delicate organs of sense. They are provided at their free extremity with a long hair, and are prolonged on their inner side into fine processes which penetrate into the deeper part of the epithelial layer of the skin or digestive wall. They eventually join a fine network of protoplasmic fibres which forms a special layer immediately within the epithelium. ”

“ Leuf, when water is taken into the full or partly full stomach, it does not mingle with the food, as we are taught, but passes along quickly between the food and lesser curvative toward the pylorus, through which it passes into the intestines. The secretion of mucus by the lining membrane is constant, and during the night a considerable amount accumulates in the stomach ”

“ Cold mucus from the throat. Much mucus, of rather a saline taste, and less inspissated than usual, is evacuated from the fauces by hawking, owing to the deficient absorption of the thinner parts of it. This becomes a habit in some elderly people, who are continually spitting it out of their mouths; and has probably been brought on by taking snuff, or smoking tobacco; which by frequently stimulating the fauces have at length rendered the absorbent vessels less excitable by the natural stimulus of the saline part of the secretion, which ought to be reabsorbed, as soon as secreted. ”

“ The cells lining the oesophagus resemble ectodermal cells; those lining the stomach are nearly all gland-cells, and obviously secrete the digestive juice. The powerful muscles of this portion of the gut produce a strong peristalsis which thoroughly mixes the juice with the food, and in the thin-walled intestine absorption of the digested material takes place. ”

“ Food in the stomach and air in the lungs, although surrounded by the body, are still outside of what is called the body proper. To gain entrance into the body proper, a substance must pass through the body wall. This consists of the skin on the outside and of the mucous linings of the air passages and other tubes and cavities which are connected with the external surface.
To get from the digestive organs into the blood, the nutrients must pass through the mucous membrane lining these organs and also the walls of blood or lymph vessels. ”

“ If liquids washed away the mucus from the mucous membrane, the throats of many individuals ought to be very harsh and dry, inasmuch as six to eight glasses of liquids pass through their mouths and throats during every day of twenty-four hours. ”

“ The first of these functions is to defend the mucous membranes from the impressions of the bodies with which they are in contact, and which, as we have ob [40] served, are all heterogeneous to the animal. Here, without doubt, we see the reason why the mucous fluids are more abundant in the cavities where these bodies remain for some time, as in the bladder, at the extremity of the rectum, &c., than in those organs through which they merely pass, as in the ureters, and in general in all the excretory ducts. ”

“ The outer layer of the skin (the epidermis) , the inmost lining of the alimentary canal, the lining of the body cavity, and the inner linings of blood-vessels, glands, and various ducts constitute our first division. The general name for such tissues is epithelium. When the cells are more or less flattened, they form squamous epithelium (Figure VI.) such as we find lining the inside of a man's cheek (from which the cells sq.ep. were taken) or covering the mesentery of various types-- sq.end. are from the mesentery (Section 16) of a frog. ”

“ Mucogen consists of all the constituents necessary for the building up of the peculiarly tender tissue called mucous membrane. These constituents are absolutely indispensible, and nature must be supplied with them if disease of the mucous membrane is to be healed by removing its cause. ”

“ The stomach has a soft, spongy appearance, and, when not distended, lies in folds. During life, it is ordinarily of a pinkish color. It is provided with numerous small glands, which secrete the gastric fluid necessary for the digestion of food. The lining membrane, when divested of mucus, has a wrinkled appearance. The arteries, veins, and lymphatics, of the stomach are numerous. ”

“ Figure 6H represents a section through the plane 820 of figure 6A. The section is caudad to one lung and cuts the extreme tip of the other, lu. The liver, li, and pancreas, pan, are seen at the side of the stomach, i ́, here cut through its greatest transverse diameter. The epithelium of the stomach varies somewhat in thickness and consists of two or three layers of cells, the variation in thickness being due to a variation in the length of the cells rather than to a variation in the number of layers. ”

“ When this organ is empty it is completely inactive; there is no secretion of the gastric juice, and the mucus, which is slightly alkaline or neutral, covers the surface; but immediately food is introduced, the mucous membrane, which was pale, at once becomes turgid, owing to the greater influx of blood; because when any organ has work to perform, it requires an increased supply. ”

“ The alkalinity of the blood circulating in the walls of the stomach prevents the digestion of the mucous membrane. If this action on the walls of the stomach is prevented in any way, the development of an ulcer is aided. ”

“ If an intestine be divided circularly in any part, its walls will be found to be composed of three principal coats or tunics, which are—commencing from the inside—the mucous, the muscular, and the serous or peritoneal, each being separated from the other by a layer of areolar tissue. ”

“ Like the skin, the mucous membranes have their chorion: it is thick on the palate, gums, and pituitary membrane, delicate in the stomach and intestines, not very distinct in the bladder, gall bladder, and excretory ducts. It appears to be formed of condensed cellular strata, strongly united, as in the skin. ”