Mucilages

MUCILAGES (Mucilagines). 1) In pharmacy, M. are called water (colloidal) solutions or extracts distinguished by high viscosity. The composition of such M. includes both proper M. (see below) and protein and many other substances, for example, starch, dextrins, pectic substances, etc. In this sense, the USSR Pharmacopoeia classifies as M.: starch M. (Mucilago, or Decoctum Amyli)—starch paste, althea M. (Mucilago, or Decoctum Althaeae)—decoction of althea root, flax M. (Mucilago, or Decoctum Lini)—decoction of flax seed, gum M. (Mucilago Gummi arabici)—solution of gum arabic, tragacanth M. (Mucilago Tragacanthae), M. of salep (Mucilago, or Decoctum Salep)—decoction or infusion of salep tubers. As a rule, M. in which it is desirable to preserve the proteins of the raw material are prepared using cold water (maceration); if the transition of starch into M. is desired, the material is crushed with a small amount of cold water to eliminate lumps, and then this paste is poured with boiling water while continuing to stir. Boiling of M. is avoided, as this results in gelatinous preparations. Among unofficial M. should be mentioned M. obtained by boiling seaweeds (Carrageen, agar seaweeds) or Iceland moss (Lichen islandicus), colloidal solutions of agar-agar, decoctions of quince seed (Cydonia), decoctions of oat or barley groats (pearl, barley), etc. All these preparations serve primarily as gentle coating agents, protecting mucous membranes. M. are often used with the aim of reducing the irritating properties of medicines (creosote, guaiacol) or their sharp taste (essential oils); they slow down the absorption of medicinal substances that are easily absorbed by the body in their pure form, but can also facilitate the absorption of water-insoluble substances by emulsifying them. Gelatinous M. of agar-agar and tragacanth, which swell greatly in water, enhance the effect of laxatives by irritating the intestine (bulky, slippery masses). M. are used as a local antidote in poisonings by alkalis, acids, phenols, and other caustic poisons. Externally, M. are used in the form of water-soluble bases for ointments (see Ointments) and in compresses for maceration of the skin. In technology, M. serve as adhesives, are used in textile production for finishing fabrics, in confectionery as emulsifiers or as part of products in the manufacture of marmalade.-2) Proper M. in the chemical sense are carbohydrates that cannot form true solutions with water; they differ from starch by the absence of characteristic forms and reaction with iodine solution, from gums by precipitability with neutral solution of lead acetate, from dextrins, glycogen, inulin, etc.—by the presence of pentoses in the molecule_gfrom pectins—by the absence of polygalacturonic acids and their derivatives. M. consist of pentosans (arabin, m-arabin, or cerasin, bassorin) and hexosans; upon hydrolysis, arabinose, fucose (methyl-pentose), xylose, rhamnose are obtained, and from hexosans most often galactose, then glucose and mannose.^-3) Protein M.—SEE Mucin, Mucilage.

I. Obergard> MUCOUS MEMBRANE (tunica mucosa, s. mucosa), a membrane lining the inner walls of hollow and tubular organs that communicate with the external environment (digestive, respiratory, urinary tracts), and secreting a mucous secretion that moistens its surface (the so-called bursae mucosae do not have a mucous membrane). The M. has a pink, pinkish-white, or grayish-white color, a smooth and slippery surface, an average thickness of 0.5 mm (from 2.2 to 0.06 and less; KSh—keg); in many organs the M. forms folds that straighten when the organ is stretched. M. develop from all three germ layers: ectoderm (portions of the digestive and urinary tracts bordering the skin), endoderm (most of the digestive tract, respiratory tract, urinary bladder, urethra), and mesoderm (renal pelvis, ureters, tubes, uterus). The histological structure of the M. is generally the same everywhere: they consist of a superficial layer of epithelium and the underlying layer of fibrous connective tissue forming the main thickness of the membrane (proper tissue of the M., tunica propria, chorion). The epithelium is extremely diverse depending on the organ (see individual organs). Between the epithelium and connective tissue is located the basement membrane of connective tissue origin (membrana basalis), the existence of which in the urinary bladder is denied. The proper tissue of the M. consists of bundles of fibrous connective tissue with a greater or lesser admixture of elastic fibers; in areas covered with stratified squamous epithelium, it extends into the epithelium, forming papillae, in the intestine it forms villi and acquires the character of reticular tissue. In the M. there are many wandering cells, especially many lymphoid elements, which often form follicles reaching significant size (solitary follicles). The M. of the digestive tract, starting from the esophagus, is divided by a thin muscle layer (muscularis mucosae) into two floors: the proper mucous membrane and the submucous membrane (tunica submucosa); the latter differs in the looser arrangement of bundles and allows the upper layer to lie in folds. In the respiratory tract, some authors (Kolliker) describe a similar layer of elastic fibers. All M. contain glands secreting mucous secretion: unicellular in the form of goblet cells and corresponding cells located among the cylindrical epithelium, and tubuloacinar in the tunica propria or submucosa; they may be mucous (gl. muciparae), serous (gl. serosae), or mixed and are scattered throughout the digestive and respiratory tracts; in the uterus there are branched tubular glands of a special kind, in the urethra—Littré's glands. In addition, in the M. of the stomach and intestine are located digestive glands of tubular form.-The M. are abundantly supplied with blood vessels, forming capillary networks under the epithelium and around the glands; in some organs the veins form cavernous plexuses (nasal cavity, urethra). Lymphatic vessels are always present in the intestine; they serve for the absorption of fat (lacteals). Nerves—sensory, secretory, and motor (to the proper muscular membranes)—form plexuses in the deep layers; especially powerful plexus is located in the submucosa of the intestine (tunica nervea). The olfactory membrane, representing an organ of sense, differs from other M. by the presence of neuroepithelium (see also the corresponding organs).

V. Karpov. Pathological Anatomy. Atrophy, expressed in thinning and smoothness of the M. due to a decrease in all its elements, is very often encountered in old age, with nutritional deficiencies, and with prolonged inflammations. Hyperplasia of the M. occurs in some chronic inflammations; in the uterus sometimes there is significant hyperplasia with proliferation of glands. With various disorders of M. function, a change in the nature of the epithelium may occur. Degenerative changes manifest themselves in granular and fatty degeneration of the epithelium of glandular M._gwhich occurs with severe infections and some poisonings (phosphorus, arsenic, etc.); the M. swells, becomes opaque, yellowish-gray. In the M. of the intestines, amyloidosis is also encountered. Necrosis of the M. can occur as a result of the cauterizing action of high temperature and chemical substances, and also occurs from pressure (bedsores of the M. of the larynx, large intestine)_gwith cessation of blood circulation (strangulations of the intestine) in some inflammations. From circulatory disorders in the M., very often there is passive hyperemia, causing cyanosis of the M. Hemorrhages into the M. are observed from the most diverse causes (trauma, hemorrhagic diathesis, inflammation, vasomotor disorders); in some organs (stomach) hemorrhage into the M. results in the formation of a defect called a hemorrhagic erosion, from which a chronic ulcer can subsequently form. Rapidly developed and widespread hemorrhage into the M. is sometimes called apoplexy (e.g., apoplexy in the M. of the uterus in elderly women). Edema causes thickening of the M., usually uneven, with individual protruding translucent swellings. Inflammatory processes of the M. mainly belong to catarrhs, other forms are also noted (see Inflammation). Chronic inflammations of the M. most often proceed as atrophic catarrh with thinning, smoothing of the M. or as hypertrophic catarrh, in which the M. undergoes uneven thickening; in the latter type of cases, proliferation of the M. is often expressed in the formation of polyps, papillae. Tumors of the M. are mainly characterized by epithelial neoplasms; from benign ones—polyps, papillomas, adenomas; from malignant ones—cancers, built from one or another epithelium depending on the nature of the epithelium covering the mucous membrane. In type, appearance, and course, cancers of the M. are extremely diverse. Other tumors, for example, fibromas, lipomas, myxomas, myomas, and sarcomas, are encountered in the M. less often. Relatively common in the M. of the digestive tract are angiomas (capillary and cavernous), which here are sometimes multiple.