Lecture 1: Fluid Compartments Flashcards
What is Total Body Water (TBW)?
The total amount of water in an individiuals body
How is TBW determined?
- It varies from 50-70% of body weight. Average=60%
- In an average person (70 Kg), TBW is 42kg or 42 L of water (0.60x70kg)
What is the TBW of an average person (70 kg)?
42 Kg or 42 L of water
List the percentage of water, percentage of body weight, and L of H2O in:
- Muscle
- Skin
- Blood
- Skeleton
- Muscle:76% H2O, 41.7% body weight, 22.1 L of H2O (most H2O)
- Skin:72% H2O, 18% body weight, 9.1 L of H2O (second most)
- Blood:83% H2O, 8.0% body weight, 4.65 L of H2O
- Skeleton: 22% H2O, 16% body weight, 2.5 L of H2O
Review Slide 6
List the percentage of water, percentage of body weight, and L of H2O in:
- Brain
- Liver
- Intestine
- Adipose Tissue
- Brain:74.8% H2O, 2.0% body weight, 1.0 L of H2O
- Liver: 68.3% H2O, 2.3% body weight, 1.0 L of H2O
- Intestine: 74.5% H2O, 1.8% body weight, 1.0 L of H2O
- Adipose Tissue: 10.0% H2O, 10% body weight, 0.7 L of H2O
Review Slide 6
Which tissue in the body has the largest amount of water? What is the amount?
Muscle: 76% H2O, 41.7% body weight, 22.1 L of H2O
How is the 42 L TBW (60% of body weight) seperated in the body?
Separated into the:
- Extracellular fluid (plasma and intersitial fluid)
- Intracellular fluid
What is the percent body weight and liters of H2O present in the extracellular fluid (ECF) & including its separations?
Part of the TBW
ECF
- 20% of body weight
- 14 L of H2O
Interstitial Fluid
- 75% of ECF
Plasma
- 25% of ECF
- 4-5 % body weight
What is the percent body weight and liters of H2O present in the intracellular fluid (ICF)?
Parts of the TBW
- 40% of Body Weight
- 28L of H2O
What seperates the ECF from ICF?
Cell membrane
What seperates the interstitial fluid and plasma in the ECF?
Capillary wall
In the ICF, how is the water distributed (3), and include the amounts?
ICF (28 L of H2O)
- Intracellular fluid=24 L
- Bone=3 L
- Transcellular fluid=1 L
In the ECF, how is the water distributed, and include the amount?
ECF (14 L of H2O)
- ISF and Lymph= 8 L
- Plasma=3 L
- Connective Tissue ISF=3 L
What is the only way to access and measure major fluid compartments in the body?
Through the plasma
What is used as a marker to measure TBW?
Water specifically H+ isotropes (ex. deuterium, tritium)
How are MOST fluid compartments measured?
The Standard Equation:
Compartment Volume= Amount injected/Final concentration
List the steps to calculate the Standard Equation
- Inject the marker/substance through the plasma
- Allow all the compartments to reach equilibrium
- Collect the sample again from the plasma and measure the final concentration
- Divide the amount initially injected over the final concentration to determine compartment volume
- NOTE: Inter-tissue volumes are measured indirectly (interstitial & ICF)
Marker/substance is specific to the fluid compartment being measured
For the compartments listed, what substance and equation is used to measure size?
- TBW
- ECF
- Plasma
- Blood
- TBW: HTO & D2O, Standard Equation
- ECF: Inulin & Radio-sodium; Standard Equation
- Plasma: 131 I-albumin & Evans Blue; Standard Equation
- Blood: 51 Cr-RBCs; Standard Equation
For the compartments listed, how are they measured (include equation)?
- Interstitial
- ICF
Inter-tissue volumes
- Interstitial: Indirect (ECF-Plasma)
- ICF: Indirect (TBW-ECF)
List the approx. equivalent concentrations (mEq/L) and molar concentrations (mmol/L) of plasma electrolytes
Cations
- Na+: 142.0 mmEq/L; 142.0 mmol/L
- K+: 4.3 mmEq/L; 4.3 mmol/L
- Ca2+: 5 mmEq/L; 2.5 mmol/L
Anions
- Cl-: 104.0 mmEq/L; 104.0 mmol/L
- HCO3-: 24.0 mmEq/L; 24 mmol/L
- Proteins: 15.0 mmEq/L; 1.5 mmo;/L
Assume Protein charge is positive 10
Define Osmolarity
Distinct from molarity. It measures osmoles of solute particles rather than mole of solute. The distinction is made when the compound can dissociate in solution (H2O)
What is the Osmolarity (molar concentration) Equation?
Osmolarity (molar conc.)= # atoms or charge of ions x mmol/L
Define Osmole
A unit of osmotic pressure equivalent to the amount of solute that dissociate in solution to form one mole of particles
Explain why 1 mole NaCl=2 osmole
When NaCl is dissociated in solution (H2O) it becomes 1 osmole of Na and 1 osmole of Cl=2 osmole
What is the normal plasma osmolarity
Approx. 300 mOsmoles/L of H2O
Actual amount closer to 285 but round to 300
What is the difference between Osmolality and Osmolarity?
- OsmoLALity: milimoles of solute/Kg of H2O
- OsmoLARity: millmoles of solue/L of H2O
As Osmolality increases, activity of H2O _____________
decreases
What does the Colligative Properties of Solution depend on?
The number of molecules and not on their nature
List the 4 Colligative Properties of Solution
- Boiling Point
- Freezing Point
- Vapor Pressure
- Osmotic Pressure
Using the image below, Which compartment have higher osmotic pressure?
A. the more particles the higher the osmotic pressure
Using the image below, which compartment does the H2O have the highest activity?
B. Activity of H2O increases as Osmolality decreases
Usint the image below, what is the direction of the water flow?
B to A. Move from high H2O activity to low H2O activity
Which cation has the highest concentraton in the ECF (Plasma & Interstitial fluid)?
Na+
- Plasma: 142.0 mmoles/L
- Interstitial fluid: 145.1 mmoles/L