From Big Medical Encyclopedia

URINATION (mictio; synonym: uresis, urinatio) — any, periodically coming act of bladder emptying. In M.'s implementation the main part is taken by the unstriated muscles of a bladder extending to an urethra at men to a seed hillock (hillock); women to an outside opening have urethras. In M. cross-striped muscles of a crotch, a prelum abdominale and urinogenital diaphragm have smaller value. M.'s act is preceded by processes of deduction of urine and adaptation of a wall of a bladder to the changing volume of its contents. Preservation of an autonomous tone and accommodation to the urine coming to a cavity of a bubble is inherent in unstriated muscles of a bladder. It provides accumulation of urine and constancy of intravesical pressure at the level which is not interfering intake of urine on ureters. Deduction of urine in a resting phase is carried out by a neck of a bladder at the expense of an autonomous tone inherent in unstriated muscles. At a tension, overflow of a bladder deduction of urine requires reduction of muscles of a crotch and urethra. The role of muscles of a crotch and urethra in deduction of urine raises at injury of a neck of a bubble (e.g., after a prostatectomy). J. Lapides with soavt, showed that a certain length of an urethra is necessary for deduction of urine. In a resting phase urine keeps in a bubble with a length of urethra of 0,5 cm. During the filling of a bubble, increase in intra belly pressure the extent of an urethra shall be not less than 3 — 4 cm

L. A. Becker and V. M. Shumovsky (1862) in an experiment established the reflex nature of M. Proizvolnoye M. as complex multi-stage process is carried out with the participation of various parts of the nervous system: cerebral cortex (I—II zone of somatic sensitivity), subcrustal structures (area of a hypothalamus and forefront of the brain bridge); centers of lumbar and sacral segments of a spinal cord; pelvic nerves and vesical branches from a hypogastric texture, okoloorganny nodes, mechanioreceptors put in a wall of a bladder. Parasympathetic, cholinergic and beta and adrenergic neuroceptors are located preferential in walls of a bladder. Alpha receptors are hl. obr. in the field of a bottom, a neck of a bubble and an urethra. According to T. S. Lagutina, relationship intero-and eksteroretseptor at formation of a reflex of M. changes in ontogenesis.

D. F. Mahony with soavt, allocates 12 reflex processes providing all stages of the act of M. A setpoint value of each reflex process for consistently developing stages of the act of M. The first 4 reflexes provide deduction of urine due to the influences of a sympathetic nervous system oppressing reductions of a detruzor and raising a tone of a sphincter of a bladder. Reductions of a detruzor are slowed down also by the impulses going from muscles of a crotch, and the tone of a sphincter of a bubble amplifies a reflex from a mucous membrane of back department of an urethra. Owing to accumulation of urine and increase in volume of a bladder there is a deformation of the mechanioreceptors put in its wall that is an incentive by the beginning M. Potok of afferent impulses from mechanioreceptors leads to response in the form of strengthening of reduction of sphincteric educations and to the relaxation of a wall of a bubble facilitating its further filling. At the volume of urine exceeding 150 ml, intensity of irritation of receptors of a bubble increases and the feeling of a desire on M can appear. The acute need for bladder emptying usually comes at accumulation in it of 350 — 400 ml of urine, however this volume is subject to considerable individual fluctuations. Reduction of a detruzor happens under the influence of the efferent impulses arriving on fibers of the pelvic nerves belonging to a parasympathetic nervous system. Reduction begins in the field of a bottom of a bubble that leads to opening of an internal opening of an urethra. The M starts to pressure drop in a bladder that could stop further release of urine, however the following reflex processes come into effect, and the second stage of the act of M. which is characterized by relaxation of muscles of a crotch and urethra for pulse counting, coming from walls of a bladder begins. At the same time reduction of a bladder strengthens irritation of the mechanioreceptors put in it. On the other hand, stretching of an urethra reflex causes further reduction of a detruzor of a bladder. The arisen closed circuit of reflexes functions before full bladder emptying. With reduction of its volume the initial source of the specified reflexes is switched off. There is a last reflex leading to reduction of perineal and pelvic muscles, relaxation of a bladder and resuming of a phase of its filling. At premature weakening of irritation of receptors the outside sphincter can be closed before full bladder emptying. The push of urine by inertia expanding an urethra excites an uretrodetruzorny reflex again, and M. renews. It is possible to accelerate consciously bladder emptying by repeated any reductions of muscles of a crotch, creating at the same time the rhythmic fluctuations of current of urine strengthening according to P. Magasi, excitement of receptors of an urethra.

The specified reflex processes are not limited to limits of a bladder, urethra and muscles of a crotch. M.'s act joins also others fiziol, systems of an organism. Thanks to participation of skeletal muscles the pose facilitating M. is created, due to reduction of muscles of an abdominal wall and a diaphragm intravesical pressure increases. The last circumstance is especially important when pressure, necessary for M., cannot be provided with reduction of a bladder. Dynamics funkts, conditions of a bladder causes reflex changes of activity of kidneys (size of a diuresis, concoction of urine), fluctuations of the ABP, a respiration rate, intensity of sweating. At the diseases which are followed by permanent frustration of M., these reflexes amplify and attract to secondary changes of the specified bodies and systems. M.'s dysfunction can have a neurogenic origin and result from inborn defects, damages or diseases of a head, spinal cord, extra-and intramural conduction paths of a bladder. M.'s disturbances at the same time are various in a form and intensity depending on localization, weight and duration of damages of a nervous system. Initial stages of neurogenic frustration of M. carry funkts, character. Deeper defeats of a nervous system lead to organic changes of uric ways: deformations of ureteric and vesical segments with development vesicoureteral ref luxury, to fibrous change of muscles of a bubble and disturbances of its sokratitelny ability, the stenosing processes in a zone of a puzyrnouretralny segment. These changes usually are followed by permanent disturbances of M., pain, tenesmus, an ischuria or its involuntary allocation, frequent desires (see. Dysuria , Ischuria , Incontience of urine , Pollakiuria ). M.'s disturbances often arise also at malformations, injuries, inflammatory diseases and new growths of the lower uric ways and a prostate (see. Bladder , Urethra ).

Diseases of various nature can be followed by frustration of M, identical in a form. Therefore for etiol, and the pathogenetic analysis of the arisen M.'s frustration comprehensive examination of patients is necessary (see. Inspection of the patient, urological ). Methods of a research can be divided on clinical (with inclusion nevrol, inspections), endoscopic (uretrotsistoskopiya), X-ray radiological (a miktsionny uretrotsistografiya, an isotope tsistorenografiya) and functional (an urofloumetriya, a tsistometriya, a rectal manometriya, a periurethral electromyography). Urofloumetriya (see) allows to estimate totally objectively M.'s act on key parameter — rate of volume flow of M. Comparison of urofloumetrichesky indicators to data of a tsistometriya allows to calculate a profile of urethral resistance, current of urine and sokratitelny ability of a muscle of a bladder. Simultaneous tonometry in a rectum and electromyography (see) reveal extent of participation of skeletal muscles during various periods of M. The same disease (e.g., adenoma of a prostate, a contracture of a neck of a bladder) can be followed by damage of various receptors of a wall of a bladder. The nature of these defeats is established, carrying out uroflou-and a tsistometriya against the background of influences by neurotropic drugs. The obtained data on the prevailing dysfunction of cholinergic, beta or alpha and adrenergic neuroceptors use for a rational pharmakol, correction funkts, changes of M. Selective use of anticholinergic, adrenergic means, alpha blockers contributes to normalization of M. At disturbances of M. caused by the stenosing disease of an urethra a reasonable operative measure is shown pathogenetic.

Bibliography: Becker L. A. and Shumovsky B. M. Definition of activity of the muscle distilling urine Medical vestn., No. 39, page 375, No. 40, page 383, 1862; Derzhavin V. M., Vishnevskiye. L. and at with e in B. S. Influence beta adrenergiche-skikh mediator funds for function of a detruzor, Urol, and nefrol., No. 5, page 3, 1976; The Guide to clinical urology, under the editorship of A. Ya. Pytel, page 111, M., 1969; Savchenko H. E. and Solonenko A. D. Functional pharmacological trials of a bladder are normal also at neurogenic frustration of an urination, Zdravookhr. Belarus, No. 11, page 27, 1973; X and yu t and V. M N. About conditions of irritation of mechanioreceptors, in book: Vopr, fiziol, interoceptions, under the editorship of. To. M. Bykova, century 1, page 540, M. — L., 1952; Jonas U. Pathophysiologie von Blase und Urethra, Urologe, Bd 17, S. 80, 1977; Khanka O. P. Disorders of micturition, Urology, v. 8, p. 316, 1976, bibliogr.; Magasi P. Neuere Auffassung iiber den Miktionmecha-nismus, Acta chir. Acad. Sci. hung., Bd 18, S. 231, 1977; MahonyD.F., Laferte R, O. a. Blais D. J. Integral storage and voiding reflexes, neurophysiologic concept of continence and micturition, Urology, v. 9, p. 95, 1977, bibliogr.; Schultheis Th. u. Rutishauser G. Kontinenz und Miktion, Z. Urol., Bd 56, S. 191, 1963, Bibliogr.

K. A. Velikanov.