In this video lecture, educator describes the Introduction to Compartment functions, Regulation of body fluid volume, Constituents of the extracellular fluid, Acid-base balance, and Control of fluid exchange between extracellular and intracellular compartments.
Water loss by the kidneys is most important means to balance between water and electrolyte intake and output. Urine volume can be as low as 0.5 L/day in a dehydrated person or as high as 20 L/day in a person who has been drinking tremendous amounts of water. Adjusting the excretion rate to match precisely the intake of these substances, as well as compensating for excessive losses of fluids and electrolytes that occur in certain diseases.
Ionic Composition of Plasma and Interstitial Fluid Is Similar. Osmosis is the net diffusion of water across a selectively permeable membrane from a region of high water concentration to one that has a lower water concentration.
The total number of particles in a solution is measured in osmoles. One osmole is equal to 1 mole (6.02 x 10^23) of solute particles. If a molecule dissociates into two ions such as sodium chloride ionizing to give chloride and sodium ions, then a solution containing 1 mol/L will have an osmolar concentration of 2 osm/L. 1 mole of glucose in each litre has a concentration of 1 osm/L. Likewise, a solution that contains 1 mole of a molecule that dissociates into three ions, such as sodium sulphate (Na2SO4), will contain 3 osm/L. Thus, the term osmole refers to the number of osmotically active particles in a solution rather than to the molar concentration.
In general, the osmole is too large a unit for expressing osmotic activity of solutes in the body fluids the term milliosmole (mOsm), which equals 1/1000 osmole, is commonly used. Osmolality when concentration is expressed as osmoles per kilogram of water. Osmolarity when concentration is expressed as osmoles per litre of solution. Osmotic pressure is the precise amount of pressure required to prevent the osmosis.
Excess fluid accumulation in the extracellular spaces causes abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries and failure of the lymphatics to return fluid from the interstitium back into the blood.
Increased capillary pressure may cause excessive kidney retention of salt and water, high venous pressure and venous constriction, failure of venous pumps and decreased arteriolar resistance. Decreased plasma proteins may cause loss of proteins in urine (nephrotic syndrome), Loss of protein from denuded skin areas and failure to produce proteins. Increased capillary permeability Immune reactions that cause release of histamine and other immune products, toxins, bacterial infections, vitamin deficiency especially vitamin C, prolonged ischemia and burns. Blockage of lymph return to cancer, infections (e.g., filaria nematodes), surgery and congenital absence or abnormality of lymphatic vessels.