Body Fluid Concepts Flashcards
Percentage of Body Mass as Water
50-70%
Water Sources
2
- Diet
- Tissue oxidation
Water Loss Sources
4
- Urine
- Feces
- Skin
- Lungs
Regulation of Water
Dehydration
- Regulated by increased water intake, or decreased water output
- Kidney and ADH
Total Body Water
2 divisions
Includes water inside and outside cells, in GI tract, and genitourinary tract
- Extracellular water
- Physiological: plasma and interstitial fluid
- Transcellular: epithelial membrane - Intracellular water (majority, cannot be measured)
Movement of Body Water
Based on: solubility in mebrane, ability to pass through pores or channels (size), spaces between epi/endothelial cells
Osmosis: high to low concentration
Composition of Plasma
High: Na+, Cl-
Low: protein, K+
Composition of Interstitial Fluid
High: Na+, Cl-
Low: protein, K+
Composition of Cell Fluid
High: K+, protein
Low: Na+, Cl-
Formation of Interstitial Fluid
Ultrafiltrate of plasma
- Water, small molecules, ions move: natural movement or active transport
Movement Between ISF and Plasma
Filtration across capillary membranes
High blood pressure: moves out of vessel into ISF
High interstitial fluid osmotic pressure: moves out of vessel into ISF
High osmotic pressure of blood: moves out of ISF into vessel
High interstitial fluid hydrostatic pressure: moves out of ISF into vessel
Starling’s Law
- Peff = (blood hydrostatic pressure + ISF osmotic pressure) - (ISF hydrostatic pressure + blood osmotic pressure)
- Peff of arteries = (35 + 0) - (2 + 25) = 8 mm Hg, fluid moves from plasma to ISF
- Peff of venous = (15 + 3) - (1 + 25) = -8 mm Hg, fluid moves from ISF to plasma
Positive value: moves out to plasma
Negative value: moves into ISF
Decreased ISF (Increased ICW)
Due to low Na levels
ISF osmo pressure lowered
- Overhydration of cells
- Water intoxication
Increased ISF (Decreased ICW)
Causes
- High Na levels
- Loss of plasma proteins
- Increased venous pressure
- Increased capillary permeability
- Dehydration of cells
- Edema
