Fluid Balance

Fluid compartments

Fluid in the compartments osmolarity of all three fluid compartments is always the same, normally mosm. It will always equilibrate until it is the same in all three compartments each compartment is separated from each other by a semipermeable membrane

In the previous image: the cell membrane of the red blood cells separates ________ from ____________. the capillary membrane separates ________ from ___________ the cell membrane of cells located in the tissue separates _________from ___________

Factors) Governing Movement of Fluid Between Compartments Osmosis Balance between hydrostatic and colloidal osmotic pressure (cop) Capillary permeability

Osmosis Depends on level of sodium ions in the fluid compartment. if Na+ increases in intravascular then (because of osmosis) fluid will be pulled from interstitial and intracellular if Na+ decreases in intravascular then (because of osmosis) fluid will shift from intravascular into interstitial and intracellular

The kidneys play an important role in regulating the concentration of Na+

Role of colloids colloids are large proteins albumin, synthesized by liver, mostly responsible for maintaining colloidal osmotic pressure in intravascular fluid compartment.

Balance between hydrostatic and colloidal osmotic pressure Hydrostatic pressure works within the intravascular compartment to push fluid out into the interstitial as blood enters capillary fluid is pushed out into interstitial tissue (because hydrostatic pressure is greater than cop at this point.) At the end of the capillary, most of the fluid is pulled back in (because hydrostatic pressure has dropped and cop is now greater)

Making tissue fluid The balance of hydrostatic and osmotic pressures in the capillaries is very delicate. an average 20 mm rise in capillary pressure causes an increase net filtration pressure which results in 68 times as much net filtration of fluid into the tissue spaces as normal, Fluid accumulation in tissues is oedema

FACTORS AFFECTING FORMATION OF TISSUE FLUID If capillary pressure is very low, net reabsorption into the blood increases at the expense of the tissue fluid volume. Increasing or decreasing the protein concentration in the blood also profoundly affects capillary exchange.

Inorganic ions Extra cellular electrolytes mEq/L Intracellular electrolytes mEq/L Plasma mEq/L Cations Sodium Potassium Calcium Magnesium Anions Chloride Sulphate Bicarbonate Phosphate The concentration of various electrolytes in body compartments is different and shown in table.

Function of Electrolytes in body; To maintain acid-base balance in body To control osmosis of water between body compartments For transmission of nerve impulses For contraction of muscles For secretion of hormones and neurotransmitters To generate action potential and graded potentials