ALIMENTARY SYSTEM, digestive device [apparatus digestorius (systerna digestoritim) (PNA), systema digestorium (JNA), apparatus digestorius (BNA)] — the set of the interconnected bodies providing processing of the food necessary for life activity of an organism.
P.'s bodies of page connected in a uniform anatomic and functional complex form the digestive channel which length at the person makes 8 — 12 m. This channel beginning an actinostome consistently consists of an oral cavity, a throat, a gullet, a stomach, a small and large intestine and comes to an end with an anal orifice (fig. 1). Channels of a set of the small glands located in its wall and also channels of the large digestive glands (sialadens, liver, pancreas) lying beyond its limits fall into the digestive canal. Digestion and absorption of food requires certain time. In this regard throughout a digestive tract there are special closing devices capable «to close» this or that department of the digestive channel. Sphincters and valves belong to such devices: the esophageal and gastric sphincter, a sphincter of the gatekeeper, the ileocecal valve, sphincters of a colon, anal sphincters, etc., the majority of which comes to light radiological at the living person (fig. 2). Passing of a food lump across the digestive canal happens due to activity of a muscular coat in hollow bodies of P. of the village having motor function.
Data on P.'s structure of page appeared long ago. Already in Ancient Egypt the persons making ritual embalming knew the main bodies of P. of page Hippocrates the special treatise «About Glands» is written. Gerofnl (Herophilos, sort. apprx. 300 AD) allocated and described a duodenum. Considerably later K. Baugin described the ileocecal valve, J. Morganyi — anal bosoms and columns, II. To Mecca — a diverticulum of an ileal gut, I. Brunner — glands of a duodenum, I. Liberkyun — intestinal crypts, Azel - whether (G. Aselli, 1581 — 1626) — intestinal limf, vessels, P. Langergaps — the endocrine device of a pancreas.
The big contribution to the doctrine about P.'s structure of page was made by domestic scientists. In the first textbook of anatomy in Russian (1757) M. I. Shane (1712 — 1762) are in detail described P.'s bodies of page and their functional purpose is specified. A. P „Protasov investigated a structure and activity of a stomach that found reflection in its thesis «Anatomo-fiziologichesky reasonings on action of a human stomach on food eaten by it» (1763). N. I. Pirogov in the atlas «Topographical and N and weary I illustrated by the cuts made in three directions through the frozen human body» the first presented exact topography of bodies of P. of page, described a sphincter of a colon. The Soviet morphologists V. N. Shevkunenko, V.P. Vorobyov and N. G. Kolosov investigated sources of an innervation and the intraorganic nervous device P. of page, G. M. Iosifov and D. A. Zhdanov studied it limf, system, A. N. Maksimenkov gave the anatomo-functional characteristic of the major sphincters of P. of page (under its edition in 1972 there was a capital work «Surgical Anatomy of a Stomach»).
A comparative anatomy
in process of development of organisms the separate systems providing this or that function form. So, P. of page stands apart for the first time at coelenterates. At flat worms, except P. of page, the secretory system is formed, and annlides have a primitive respiratory system (outside gills). The digestive channel already at worms is subdivided into the front, including oral cavity, average and back departments, to-rye at vertebrata gain further development. Reptiles had a division of an oral cavity by means of the sky on primary nasal cavities and a mouth. At mammals the circle of an actinostome includes the muscles capable to close a mouth. Depending on a way of food nek-ry parts of the digestive canal significantly become complicated. So, the stomach of ruminant is divided into a number of departments: hem, ventral bag, grid, book, abomasum etc. Depending on character of food length of intestines — at herbivorous animals it longer changes. There is a complication of a structure of digestive glands.
At a germ of the person on 3 — the 4th week of embryonic development is formed primary gut having two layers: internal (mucous membrane), formed by an entoderm, and outside (muscular and serous covers), formed by a visceral mesoderm. After an otgranicheniye of a body of an embryo from an extraembryonic part of germinal leaves and formation of a perigastrium allocate three departments in primary gut: front, average and back gut. At 4 — 5 weeks embryos on a body surface in the head and in a caudal part two poles appear, to-rye gradually go deep prior to a meeting with the blind ends of primary gut, and then break, forming oral and cloacal openings. The foul place is divided further into proctal and urinogenital openings (see. Urinogenital system ). By the end of the 2nd month of embryonic development the front gut of a kzada from future throat is narrowed, turning into primary gullet. Kaudalny a gullet the gut extends and forms primary stomach. The average kpshka and a back gut will be transformed to intestines. During the same period of development below a stomach from an average gut outgrowths — rudiments of a pancreas and liver appear.
At newborns P.'s bodies of page do not reach still final a form and situation. So, eruption of milk (temporary) teeth is noted in terms from 6 months to 2,5 years, and constant from 6 to 25 years. The gullet has no bends, the created narrowings. The stomach of a spindle-shaped form, lies almost vertically. Intestines rather short, ileocecal corner are located highly, the caecum small and lies almost under a liver. With age the digestive channel is gradually extended, observed omission of its mobile departments (a stomach, intestines).
Normal digestion (see) it is made with the assistance of all bodies of P. of page. The functional linkage of these bodies is carried out thanks to the specialized nervous devices located in various bodies, to-rye can register structure of food, extent of its processing and assimilation.
In an oral cavity (see. Roth, oral cavity ) with the help teeth (see), chewing movements of jaws and language (see) there is a crushing and a mastication of food, and under the influence of allocated saliva (see) its softening, fluidifying and enzymatic processing is made. Sialadens (see) happen big — parotid glands (see), submaxillary gland (see), hypoglossal gland (see) and small — buccal, lingual, palatal, lip. Big sialadens are located in special receptacles and have long output channels. Small sialadens are in a mucous membrane of the relevant departments of an oral cavity, channels their short. The food processed by saliva comes through a throat and a gullet to a stomach.
Throat (see) connects oral and nasal cavities to a gullet and a throat. At the act of swallowing the soft palate closes openings of a nasal cavity, and an epiglottis and a root of language — an entrance to a throat. From a throat food gets in gullet (see) and separate portions (throats) passes on it in a stomach. Swallowing (see) is the difficult reflex act. In a gullet there is further, though short-term, a processing of food: mastication and chemical processing by its juice of esophageal glands. On site transition of a gullet to a stomach the esophageal and gastric sphincter which warns regurgitations) — the return receipt of contents of a stomach in a gullet is.
In stomach (see) the further razmelcheniye of food, its ferkhmentativno-chemical treatment is carried out gastric juice (see) and partial absorption. The stomach performs, besides, protective function since the gastric juice possesses bactericidal action. At sufficient processing of food cleavage products affect nerve terminations of a stomach; the sphincter of the gatekeeper reflex periodically opens and passes a part of contents of a stomach in a duodenum.
Duodenum (see) where output channels of intestinal glands, the general bilious channel, pancreat ducts, and a jejunum (open see. Intestines ), in which mucous membrane there is a huge amount of intestinal glands, are the main place of enzymatic processing of food. In a small bowel occurs absorption (see) the split products. The mucous membrane in a small bowel has complex structure. It folded also forms numerous outgrowths (fibers) and deepenings (crypt). The regulator of extent of enzymatic and chemical processing of food and process of absorption is the terminal department of an ileal gut and the ileocecal valve.
Big digestive glands — liver (see) and pancreas (see) — the bodies complex for the device and function. Along with participation in digestion by release of digestive juices they possess an important role in some other vital processes. So, in a liver there is a synthesis of a glycogen; she possesses the protective and neutralizing functions (neutralizes the harmful substances coming to blood), participates in regulation of water exchange. The pancreas functions and as a hemaden (see. Hemadens ).
A large intestine (see. Intestines ) is continuation thin and stretches from the ileocecal valve to an anal orifice (see. Anus ); it performs the following functions: in it there is generally an absorption of water, formation of dense contents and at some point removal it from an organism (see. Defecation ).
Pathology of bodies of the alimentary system — see articles devoted to separate bodies (e.g., Stomach , Intestines , Gullet ), and also articles on individual diseases and patol, to states (e.g., Gastritis , Hemorrhoids , Hepatitis , Duodenitis , Caries of tooth , Colitis , Proctitis , Pharyngitis , Cholangitis , Cholecystitis , Holetsistopankreatit ).
Bibliography: Diamonds I. Century and Sutulov L. S. The atlas on histology and embryology, page 359, M., 1978; Sinelnikov R. D. Atlas of anthropotomy, t. 2, page 11, M., 1979; Surgical anatomy of a stomach, under the editorship of A. N. Maksimenkov, JI., 1972; Schumacher G. H. Embryonale Entwick-Jung des Menschen, B., 1977.
S. S. Mikhaylov