Fluid And Electrolytes

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FLUID AND ELECTROLYTES


Necessary for health
Amounts in body must be maintained in normal range
Balance most important to maintain homeostasis

Proportion of body fluids

Fluid is 67 % of adult male weight
With certain disease, excess or deficits may occur
Newborn 75 % of body weight is water, at risk fluid deficit

Distribution of body water/ Fluid Compartments

Intra-cellular, ICF- 2/3 to ¾ of total body water, within the cells
Extracellular, ECF- 1/3 to ¼, outside of cells in two compartments
Intravascular – plasma
Interstitial, fluids surrounding cells, including lymph

Extracellular is transport system for nutrients and waste products to and from cells
Interstitial: fluid surrounding cells

Other body fluids secreted include saliva, bile, gastric, pancreatic, enteric
Excretions: waste produced by body
Most fluids reabsorbed, not excreted.

Body Electrolytes

ECF and ICF contain electrolytes in varying proportions.

Electrolytes are positive or negative charged ions. NaCl separates to Na+Cl
Electrolytes conduct electricity

Positive ions—cations (Na, Mg, K, Ca)
Negative ions –anions (Cl, HCO3)

ECF – mostly Na, Cl
ICF – K, HPO4
Electrolytes must be maintained in proportion to the quantities of fluids in the compartments.

Functions of electrolytes

Sodium, most abundant ECF, water balance, muscle contraction, nerve impulses
Water goes where sodium goes
Food source: salt
Regulation: by kidneys

Potassium—Most abundant ICF, regulates muscle contraction and excitability, helps maintain pH of body

Food source: fruits (bananas, oj), vegetables

Regulated by kidneys. Potassium is excreted as sodium is retained

Calcium: conducts nerve impulses, coagulation, bone growth
Small amt. in fluids, most in bones
Food: milk, dairy, green leafy veg.
Regulation: parathyroid glands

Others: see handout

Electrolytes measured in millequivalents

Lab chemistry studies ...