fluid mosaic model
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flu·id mo·sa·ic mod·el
a model for the structure of a biomembrane, with lateral diffusibility of constituents and little, if any, flip-flop motion across the biomembrane.
fluid mosaic model
A representation of the structure of the cell membrane, in which protein molecules are dispersed in a phospholipid bilayer.
See also: model
fluid mosaic modelA widely accepted account of the structure of the cell membrane, as consisting of a two-molecule layer of phospholipid with proteins embedded in it. The phospholipid layer has the physical properties of a fluid so that the proteins can move about relatively freely.
1. a liquid or gas; any liquid of the body.
2. composed of molecules which freely change their relative positions without separation of the mass.
the fluid contained within the allantois.
the fluid within the amnion that bathes the developing fetus and protects it from mechanical injury.
a state in which the volume of body water and its solutes (electrolytes and nonelectrolytes) are within normal limits and there is normal distribution of fluids within the intracellular and extracellular compartments. The total volume of body fluids should be about 60% of the body weight, and it should be distributed so that one-third is extracellular fluid and two-thirds intracellular fluid. Although this distribution remains constant in a healthy animal, there is continuous movement of fluid into and out of the various compartments. See also dehydration, water intoxication.
the fluids within the body, composed of water, electrolytes and nonelectrolytes. The volume and distribution of body fluids vary with age, sex and amount of adipose tissue. Throughout life there is a slow decline in the volume of body fluids; obesity decreases the relative amount of water in the body.
Although the body fluids are continuously in motion, moving in and out of the cells, tissue spaces and vascular system, physiologists consider them to be 'compartmentalized'. Fluid within the cell membranes is called intracellular fluid and comprises about two-thirds of the total body fluids. The remaining one-third is outside the cell and is called extracellular fluid. The extracellular fluid can be further divided into tissue fluid (interstitial fluid), which is found in the spaces between the blood vessels and surrounding cells, and intravascular fluid, which is the fluid component of blood.
The maintenance of a proper balance between the intracellular and extracellular fluid volumes is essential to health. In patients with heart failure and renal failure the balance becomes upset, producing either localized or generalized edema. Excessive fluid loss produces fluid volume deficit causing cellular dehydration and impaired cellular function.
a histological fixative.
the fluid contained within the ventricles of the brain, the subarachnoid space, and the central canal of the spinal cord. See also cerebrospinal fluid.
see fluid dram.
a liquid preparation of a vegetable drug, containing alcohol as a solvent or preservative, or both, of such strength that each milliliter contains the therapeutic constituents of 1 gram of the standard drug it represents.
allantoic plus amniotic fluids.
the extracellular fluid bathing the cells in most tissues, excluding the fluid within the lymph and blood vessels.
having the same tonicity or osmotic pressure as blood.
aqueous fluid secreted by the lacrimal glands; called also tears.
in radiographs, the interface between fluid and gas, as in the gastrointestinal tract, will show as a straight line.
by vomiting, diarrhea, polyuria, water deprivation. See dehydration.
fluid mosaic model
the modern concept of the structure of a biological membrane developed by S.J. Singer and G.L. Nicolson. In it the membrane consists of protein molecules partly embedded in a discontinuous bilayer of phospholipids that form the matrix of a mosaic of functional cell units.
see fluid ounce.
pericardial, pleural, peritoneal fluid
normally present in amounts sufficient only to lubricate the movement of viscera within the respective cavities. Composition similar to blood serum.
see fluid therapy (below).
the limitation of oral fluid intake to a prescribed amount for each 24-hour period.
the fluid within the spinal canal.
fluid splashing sounds
audible when gas and fluid are free in a cavity, e.g. abomasum in cases of abomasal displacement; can be elicited by shaking a small animal or part of a large animal (i.e. succussion) or by simultaneous percussion and auscultation.
aims to replace fluids lost by disease process or by restriction of intake, or to maintain a high rate of fluid excretion to ensure removal of toxins, or to administer therapeutic or anesthetic agents slowly over a long period. The amounts and route of administration vary with the need of the patient. Normal solutions include 5% dextrose and Ringer's solution; alkalinizing fluids include lactated Ringer's and 1.3% sodium bicarbonate; acidifying solutions include isotonic saline and 1.9% ammonium chloride.
fluid volume deficit
an imbalance in fluid volume in which there is loss of fluid from the body not compensated for by an adequate intake of water. The major causes are: (1) insufficient fluid intake, and (2) excessive fluid loss from vomiting, diarrhea, suctioning of gastric contents, or drainage through operative wounds, burns or fistulae. Decreased volume in the intravascular compartment is called hypovolemia. Because water moves freely between the compartments, extracellular fluid deficit causes intracellular fluid deficit (cellular dehydration), which leaves the cells without adequate water to carry on normal function.
fluid volume excess
an overabundance of water in the interstitial fluid spaces or body cavities (edema) or an excess of fluid within the blood vessels (hypervolemia) and water intoxication.
Factors that contribute to the accumulation of edematous fluid are: (1) dilatation of the arteries, as occurs in the inflammatory process; (2) reduced effective osmotic pressure, as in hypoproteinemia, lymphatic obstruction and increased capillary permeability; (3) increased venous pressure, as in congestive heart failure, thrombophlebitis and cirrhosis of the liver; and (4) retention of sodium due to increased reabsorption of sodium by the renal tubules.