Body Fluid Compartments

Question 1

1. Describe the distribution of water and electrolytes within the compartments of the body. (give specific numbers regarding distribution between ICF and ICF, interstitial v. plasma volume)

Answer 1

0.6 of body weight is water
(TBW= total body water)
⅔ of TBW goes to ICF (0.4 x wt.)
⅓ of TBW goes to ECF (0.2 x wt.)

¾ of ECF goes to interstitial fluid (0.15 x wt.)
¼ of ECF goes to plasma (0.05 x wt.)

(wt. is lean body weight)

Question 2

2. Identify the factors that affect the distribution of fluid among body compartments. (compare the osmolarity of compartments

Answer 2

compartments are separated by semipermeable membranes and water moves freely between compartments so that the effective osmolarity is the same

if you add a solution that is not isotonic to either compartment, you will effect both compartments

Note: proteins and Mg do not exert osmotic force

Question 3

3. Assess the volume in each of the body compartments. Describe the characteristics of ICF: solutes and what can cause change in volume.

Answer 3

major solutes are K+, phosphates and proteins

changes in sodium concentration change the ICF volume

Question 4

4. Explain the mechanisms that lead to an imbalance in distribution of fluid or in the amount of fluid in a compartment.

Answer 4

ingestion of water or salts can cause fluid shift between compartments also dehydration, solute or fluid loss

to understand what the balance will be after a disturbance, calculate the original osmoles and volume of ECF and ICF, calculate the new volume and osmoles given the disturbance understanding that osmolarity= osmoles/volume

Question 5

Contrast osmolarity and osmolality.

Answer 5

osmolarity: osmoles of solute per liter of solution
osmolality: number of osmoles per kg of solvent

Question 6

Compare the body water content of muscular v. fat patients.

Answer 6

more water in muscle than fat, fat excludes water (note: men typically have a higher muscle content)

Question 7

3. Assess the volume in each of the body compartments. Describe the solutes and effects of solute change in the ECF.

Answer 7

major solutes include Na, Cl- and bicarbonate
ECF includes both intravascular (plasma) and extravascular (interstitial) volume

changes in sodium content (not concentration) effect ECF

Question 8

3. Assess the volume in each of the body compartments. Describe the symptoms and signs of changes in ECF.

Answer 8

symptoms:
thirst- angiotensin II
lightheadedness- low volume
palpitations- low volume

signs of low volume:
orthostasis (change in BP more than 20mmHg between standing and laying down)
decreased BP
urine output decrease
dry mouth
dry axilla
low JVP (significant for intravascular volume)
skin turgor/ edema (significant for extravascular and interstitial vol.)

Question 9

What would happen to cells with isotonic, hypertonic or hypotonic solutions added to the intravascular compartment?

Answer 9

isotonic- not moment of water between compartments, ECF volume increases

hypotonic- movement of water into ICF from ECF; will raise ECF volume, and decrease serum osmolality, increase ICF volume

hypertonic (higher tonicity in comparison to the ECF)- movement of water from ICF to ECF; will raise ECF volume and increase serum osmolality and decrease ICF volume

Question 10

ECF osmolarity and tonicity are _____ (how are they related), where as ICF osmolarity and tonicity are ________

Answer 10

ECF osmolarity and tonicity are independent

ICF osmolarity and tonicity are intimately tide together