From Big Medical Encyclopedia

LIQUIDS — the bodies which are in aggregate state, intermediate between firm and gaseous states, keeping separate lines of both a solid, and gas and at the same time possessing a row only it inherent features

. divide on simple (one-component atomic., liquid pure metals, the liquefied inert gases, unpolar. — benzene, chloroform) and difficult (e.g., the water which is the most universal solvent).

Like solids. keep the volume, have a free surface, have a certain tearing strength at stretching, are characterized by the high density and small compressibility, existence of strong intermolecular interaction, heat capacity and conductivity. For liquids, behind an exception liquid crystals (see), such properties as isotropy are characteristic (independence physical. properties from the direction) and the flowability, i.e. ability it is easy to change external shape under the influence of small loadings (see. Rheology ).

Strong intermolecular interaction cause existence on border. with any other environment surface intention (see). Under the influence of internal pressure a surface layer. aims at reduction —. at the invariable volume takes such form, at a cut its surface is minimum (spherical shape of drops).

Thermal agitation of molecules in liquids consists of a combination of oscillating motions and jumps of molecules from one provisional regulations of balance (the centers of fluctuations) in others. The time spent of a molecule in this equilibrium situation is designated «time of settled life of a molecule». In a liquid phase of substance it is time it is small, and in a solid phase it is almost infinite. For implementation of jumps of each of molecules it is necessary to report the activation energy sufficient for a rupture of its bonds with surrounding molecules and transition to an environment of other molecules (see. Solutions , Solvation ). Thanks to such jumps there is a hashing of molecules Zh.

In polar., in addition to interattraction between molecules, inherent and to unpolar molecules, also interaction between various parts of molecules bearing electric charge that results in non-equivalence of various mutual provisions of molecules takes place. The situation answering to mutual pushing away of both ends of molecules will be unstable. The situation answering to strengthening of interattraction between molecules is preferential and remains longer in time: it corresponds to bigger mutual coherence of molecules, formation of complexes. Similar complexes from polar molecules may contain two and more molecules. Such. are called associated; the dipole moments other than zero, and dielectric permeability have their molecules (see) depends on temperature (water, alcohols, etc.). Nonassociated. have small values of dielectric permeability, the edge does not depend on temperature; dipole moments of their molecules are equal to zero (hexane, benzene, etc.). The size of dielectric permeability at. can be from 2 (unpolar hydrocarbons) to 81 (water).

By methods X-ray crystallographic analysis (see) and neytronografiya it is established that at the room temperature in liquids orderliness in an arrangement of molecules is observed nek-paradise (a so-called near order which is shown in interrelation of situation and orientation of close located groups including two and more molecules). However such orderliness extends to area protyazhennostyo about several interatomic distances whereas in crystals frequency of an arrangement of particles is characteristic of all volume (a so-called distant order). In .vzaimny provisions and orientations of molecules the uniformity and isotropy inherent to liquids is explained by lack of a distant order.

Heat capacity of liquids is close to heat capacity of solids and slowly changes with a temperature. Measurement of heat capacity serves as method of a research of phase transformations. Coefficients of heat conductivity and viscosity (see) decrease with growth of temperature since intermolecular interactions obstruct any relative traffic between two adjacent layers. Conductivity of one-component. it is usually small, for * an exception of liquid metals and electrolytes (see).

Biological liquids

Biological liquids include blood, a lymph, cerebrospinal and synovial., breast milk, digestive juices, sweat, urine, etc. In the list of all these. free water enters. In different bodies and fabrics water content on a weight unit is unequal: it least of all in bones (20%), is most big and is constant in blood (81%). Water is the main environment, in a cut the metabolism of organisms, and also transport of various substances from one body to another proceeds. Water is the main substrate of various metabolic processes, carries out physical. thermal control (see Sweating) and other processes of life activity (see. Water , Water salt metabolism , Mineral metabolism , Metabolism and energy ). Life without water is impossible: deprivation of water can lead to the death of the person in several days while at a complete starvation and unlimited ingress of water preservation of human life even within 40 — 45 days is possible.

One of the main. an organism is blood (see), it possesses the major role in maintenance homeostasis (see). With a blood flow nutrients and oxygen are delivered to fabrics, end products of a metabolism, including and carbon dioxide gas are carried away from fabrics; blood, being the major factor immunity (see), performs protective function.

On limf, system of vertebrate animals and the person the lymph — liquid with the chemical structure close to structure of a blood plasma, cerebrospinal, synovial and to other liquids of an organism circulates. In a lymph usually there are no erythrocytes, but there are always lymphocytes (see. Lymph ). Peculiar internal environment of c. the N of page is the cerebrospinal liquid, or liquor which is carrying out barrier function (see). With its help composition of salt in solution and a fixed level of osmotic pressure of a brain are maintained; it is a medium of a brain etc.

Is in joints and tendinous vaginas synovial fluid (see). It is allocated with an internal cover of a joint cavity and works as lubricant, on structure is similar to a lymph, but contains a small amount slime (see).

Products of exchange final, unnecessary an organism are brought out of it with the help urine (see). Its volume changes depending on a condition of an organism (see. Diuresis ).

In the period of a lactation mammary glands develop breast milk (see). It contains proteins, fats, carbohydrates, vitamins A, B, C, D, mineral substances (Ca, Mg, P, etc.), the antibacterial agents and antibodies promoting emergence of oroimmunity at the child eating milk. Apprx. 87% of total quantity of this. water makes.

Digestive juices (saliva, gastric, pancreatic and intestinal juice, bile) produced by special glands of a digestive tract are necessary for processing of food therefore the nutrients which are contained in it are soaked up and acquired by an organism.

Bibliography: Abas-Zade And. and Bagdasaryan S. Introduction to fluid physics, Baku, 1961; Willie K. and Detye V. Biologiya, lane with English, M., 1974, bibliogr.; Kireev V. A. Short course of physical chemistry, page 161, etc., M., 1970; Human physiology, under the editorship of E. B. Babsky, M., 1972.

Yu. A. Zhukov.