From Big Medical Encyclopedia

RUDIMENTAL ORGANS (Latin rudimentum a rudiment, a fundamental principle) — anatomically and functionally changed bodies owing to loss of the value by them in the course of historical development of an organism. Rubles of the lake arise, as a rule, in an embryogenesis therefore they are better expressed during pre-natal development and right after the birth. On the origin they most often are the remains of bodies, to-rye functioned at predecessors or ancestors.

Interest in R. of the lake arose at the beginning of 19 century during origin theory of evolution (see). Nek-ry researchers saw the reason of an origin of R. of the lake in a lack of nutrients in the period of embryonic development of a germ. In theory of evolution of Ch. Darvin crucial importance in R.'s origin of the lake is allocated for natural selection, as a result to-rogo advantage keep the bodies providing more effective functioning of an organism, its survival. The bodies which lost functional superiority do not develop further, though are put during the formation of individuals, i.e., across Darwin, inaction of body dooms him to a rudimentation. Thus, the rudimentation of bodies is a form of manifestation of regress in the nature, however, on the other hand, R.'s presence by the lake — the obligatory sign accompanying evolutionary development of living beings.

The number P. of the lake is close to hundred, at the same time with increase in the organization of an animal R.'s number of the lake increases. Degree of safety and R.'s expressiveness of the lake is very variable. Rubles of the lake remain during all life of an individual, unlike the provisional (temporary) bodies which are available only for a germ. Sometimes as a result of disturbance of embryonic development there are signs characteristic of the remote ancestors of the individual, so-called. atavisms (see), napr, a tail-shaped skin outgrowth, additional nipples, continuous indumentum at the person.

The river of the lake can be divided into three groups. In the first group R. of the lake unnecessary an organism, useless, deprived of a certain function, napr, eyes at a mole, teeth at a whale, enter-loskovy a cover of skin at the person and other.; in the second group — R. the lakes performing that function in very weak degree, edges was inherent in body at the corresponding historical stage of its development, napr, muscles of an auricle, a pyramidal muscle of a stomach; in the third group — R. the lakes which changed morphologically and joined in performance of new function, napr, a worm-shaped shoot.

At the person R. of the lake cervical edges, Mekkel's diverticulum are (see. Mekkelya diverticulum ), tailbone (see), wisdom teeth (see. Teeth ), cross palatal folds of a mucous membrane of a mouth, well-marked at children, a semi-lunar fold of a conjunctiva in a medial corner of a palpebral fissure as a rudiment of a blink membrane, rudimentary hairs on skin, etc.

the lake as bodies with the lost or strongly weakened functions do not exert any impact on life activity of a human body to R. But in nek-ry cases of R. of the lake can be the cause of diseases. So, the rudiment of a mezonefralny channel which is at 25% of newborn girls in a wide ligament of a uterus near a uterine tube at adult women can be a source of a cyst vaginas (see). Branchyogenic cyst (see) can evolve from a rudiment of a shchitoyazychny channel. In the field of a tailbone the meningocele as cystous protrusion of covers of a spinal cord meets (see. Spina bifida ). Here teratoid tumors are localized.

See also Involution .

Bibliography: Mirzoyan E. N. Development of the doctrine about reconciliation, M., 1974; III and m - to e in and the p B. M. Biological fundamentals of zoology, t. 1 — 2, M., 1923 — 1925; Shmalgauzen I. I. An organism as whole in individual and historical development, M., 1982; By of u m b i e-g e 1 I. Rudimentation, Stuttgart, 1960, Bibliogr.

V. V. Kupriyanov.