26.1 Body fluid,, fluid movement , water balancee, ECF osmolality

Body water content -

infants are 73% or more Water (low body fat, low bone mass)

Adult males are how much water

60% water

Adult females are how much water

50% water

(higher fat content, less skeletal muscle mass)

water content in body declines to what percent in old age

45% water

water is what kind.of solvent

universal

solutes are

substances dissolved in water

solutes are classified as

nonelectrolytes and electrolytes

nonelectrolytes

• most are organic molecules

  • Do not dissociate in water

  • Examples: glucose, lipids, creatinine, and urea

    • No charged particles are created

electrolytes

• Dissociate into ions in water

  • Examples: inorganic salts, all acids and bases, some proteins

• Ions conduct electrical current 

• Greater osmotic power than nonelectrolytes

comparison of extracellular & intracellular fluids

• ECF: electrolyte contents are all similar except for higher protein, lower Cl^– content of plasma

• ICF: contains more soluble proteins than plasma

• Electrolytes are most abundant (largest number) solutes in body fluids, determine -

chemical and physical reactions

• Bulk of dissolved solutes (take up most space) consists of

• proteins, phospholipids, cholesterol, and triglycerides

• 90% in plasma

• 60% in IF

• 97% in ICF

Osmotic and hydrostatic pressures regulate

continuous exchange and mixing of fluids

• ↑ ECF osmolality →

• ↓ ECF osmolality →

• water leaves cell

• water enters cell

Exchanges between plasma and IF occur across capillary walls

• Fluid leaks from arteriolar end of capillary, reabsorbed at venule end

• Lymphatics pick up remaining fluid and return it to blood

Exchanges between IF and ICF occur across cell membrane

• Two-way osmotic flow of water

• Ions move selectively into or out of cell

• Nutrients, wastes, gases have unidirectional flow

water intake must equal to

water output ; -2500 ml / day

water intake

• most water is taken in via ingested foods and beverages, but small amount from metabolism

metabolic water (water of oxidation)

water produced by cellular metabolism 

• Water output:

urine (60%), insensible water loss (lost through skin and lungs), perspiration, and feces

obligatory water losses -

explain why we cannot live w/ out water very long

water output include -

• Insensible water loss from lungs or skin

• Sensible water loss from urine to excrete wastes (60%), obvious sweat (8%), and feces (4%)