NUR 3125 Lecture Notes - Lecture 3: Plasma Osmolality, Extracellular Fluid, Vasopressin
Document Summary
Narrow range of normal to maintain electrolyte balance and ph. Tbw varies with age, gender, and weight. Newborns body weight represents 70-80% water weight. Females greater percent body fat due to estrogens role in fat storage. Males greater muscle mass and higher water concentration. Water repelled by hydrophobic fat molecules, thus obese individuals have lower percentage of fluid. Neonates and infants at highest risk for dehydration. Even with these changes high risk of dehydration. Kidney declines in ability to concentrate urine. Ecf concentration controlled primarily by sodium concentration. Net movement of water continues until equilibrium achieved. Movement of fluid back and forth across the capillary walls. Net filtration = (forces favoring filtration) (forces opposing filtration) Push fluid out of capillary to interstitial space. Capillary hydrostatic pressure (blood pressure arterial end of capillary) Major filtration force is systemic blood pressure. Resist movement of fluid from capillary to interstitial. Created by plasma proteins, venous end of capillary.
