Body Fluid Compartments

This collection of flashcards encompasses the key concepts related to body fluid compartments, including their distribution, measurement techniques, and the principles governing fluid movement and electrolyte concentrations.

What percentage of body weight is typically water in a non-obese human?

~60% of body weight is water.

What are the two main compartments of body water distribution?

Intracellular Fluid (ICF) and Extracellular Fluid (ECF).

How much of the total body water is found in the Intracellular Fluid (ICF) of a 70kg man?

~28 Liters (66.67% of total body water).

How is Extracellular Fluid (ECF) further divided in the body?

Into Plasma and Interstitial Fluid.

What is the concentration of Sodium (Na+) in the Extracellular Fluid (ECF)?

145 mEq/L.

What is the measurement principle used for determining the volume of body fluid compartments?

Dilution principle.

What substance can be used to measure Plasma volume?

131 Iodine-labelled albumin or Evans Blue dye.

What is the typical concentration range for Posm in body fluids?

285-310 mosm/kg H2O.

What defines an effective marker for measuring the volume of a particular fluid compartment?

The marker must be freely distributed, non-toxic, non-metabolized, and easily measured.

Describe the role of the capillary wall in fluid movement between plasma and interstitial fluid.

The capillary wall acts as a semipermeable membrane allowing passive movement based on concentration gradients and hydrostatic pressures.

What forces determine fluid movement across the capillary wall?

Hydrostatic pressure and colloid osmotic (oncotic) pressure.

How is Total Body Water calculated using D20 in a measurement example?

By measuring the concentration of D20 after equilibrating and accounting for losses.

What is the approximate distribution of Total Body Water in terms of body weight?

~60% body weight.

What is the role of active and passive transport in maintaining electrolyte concentration differences between ICF and ECF?

Active and passive processes help maintain differences in electrolyte concentrations across the plasma membrane.

How is excess fluid in the interstitial space managed in the body?

Excess fluid is drained into the lymphatics and returned to circulation.