Costanzo Renal Physiology: Body fluids

Question 1

What proportion of total body weight it composed of total body water?

Answer 1

60%

Question 2

What are the two major divisions of total body water?

Answer 2

Intracellular and extracellular body water.

Question 3

What proportion of total body water is intracellular fluid (ICF)?

Answer 3

Two thirds of TBW is ICF.

Question 4

What are the major cations of intracellular fluid?

Answer 4

K+ and Mg2+

Question 5

What are the major anions of ICF?

Answer 5

Protein and organic phosphates (ATP, ADP, AMP, etc.)

Question 6

What proportion of TBW is composed of ECF?

Answer 6

one third

Question 7

What is the major cation of ECF?

Answer 7

Na+

Question 8

What are the major anions of ECF?

Answer 8

Cl- and HCO3-

Question 9

Plasma makes up what proportion of ECF and TBW?

Answer 9

Plasma makes up 1/4th of ECF and 1/12th of TBW.

Question 10

What are the major plasma proteins?

Answer 10

Albumin and globulins

Question 11

What proportion of the ECF and TBW is composed of interstitial fluid?

Answer 11

Interstitial fluid makes up 3/4ths of the ECF and 1/4th of TBW.

Question 12

How is interstitial fluid both similar and dissimilar to plasma?

Answer 12

Interstitial fluid has roughly the sam composition as plasma. However, interstitial fluid has much less protein than plasm (ultrafiltrate of plasma)

Question 13

What is the 60-40-20 rule?

Answer 13

TBW is 60% of body weight
ICF is 40% of body weight
ECF is 20% of body weight

Question 14

How is the volume of fluid compartments measured?

Answer 14

The the dilution method.
A known amount of substance is given whose volume of distribution is the compartment of interest.
(1) substance is added
(2) substance is allowed to equilibrate
(3) Concentration is measured in plasma
(4) calculated by Vd = amount given/plasma concentration. (always convert to liters)

Question 15

What can be used to measure TBW?

Answer 15

titrated water, D2O, anitpyrene (distributes wherever water is found)

Question 16

What can be use to measure ECF?

Answer 16

Mannitol, inulin, Sulfate (cannot cross cell membranes to enter ICF)

Question 17

How is plasma volume measured?

Answer 17

Evans blue (a dye that binds to albumin) or Radiodinated serum albumin. (RISA)

Question 18

How is ICF measured?

Answer 18

TBW - ECF = ICF

Question 19

How is Interstitial fluid measured?

Answer 19

ECF - plasma volume = interstitial fluid

Question 20

Why does water shift between fluid compartments?

Answer 20

The osmolarity of ECF and ICF are usually equal. Water will shift between compartments to maintain this equality.

Question 21

What happens in isosmotic volume expansion?

Answer 21

If isotonic NaCl solution is added then there will be a volume increase in the ECF. However, the osmolarity will stay the same and no water will change compartments.

(1) Hct will decrease
(2) Plasma protein concentration will decrease
(3) Blood pressure will increase.

Question 22

What happens in isosmotic volume contraction?

Answer 22

Loss of isotonic fluid (diarrhea) will not cause a water shift because osmolarity will remain unchanged. However, ECF volume will be decreased.

(1) Hct will increase
(2) Plasma protein concentration will increase
(3) Arteriole blood pressure will decrease.

Question 23

What happens in hyperosmotic volume expansion?

Answer 23

In hyperosmotic volume expansion (addition of NaCl/excessive NaCl intake) the osmolarity of the ECF increases and water shifts from the ICF to the ECF to equalize the osmolarity.

(1) ICF volume decreases
(2) ECF volume increases
(3) Hct decreases
(4) Plasma protein concentration decreases

Question 24

What happens in hyperosmotic volume contraction?

Answer 24

In hyperosmotic volume contraction (excessive sweat loses more water than salt). The osmolarity of the ECF increases. ICF water flows into the ECF to equalize the osmolarity.

(1) ICF volume decreases
(2) decreased ECF volume
(3) plasma protein concentration increases (decreased ECF volume)
(4) Hct is unchanged (RBCs are more concentrated but their volume is decreased due to osmolarity change)

Question 25

What happens in hyposomotic volume expansion?

Answer 25

hyposomtic volume expansion (inappropriate antidiuretic hormone) causes a gain of ECF water. ECF osmolarity decreases and water shifts from the ECF to the ICF until osmolarity is equalized.

(1) ECF volume increases
(2) ICF volume increases
(3) plasma protein concentration decreases
(4) Hct remains unchanged (RBCs are diluted but they swell with water thus normalizing the Hct)

Question 26

What happens in hyposomotic volume contraction?

Answer 26

hyposmotic volume contraction (adrenocortical insufficiency-loss of NaCl) cuases the osmolarity of ECF to decrease. Water then shifts from the ECF to the ICF until the osmolarity is equalized.

(1) ECF volume decreases
(2) ICF volume increases
(3) Plasma protein concentration increases
(4) Hct increases (RBCs are concentrated and they swell due to decreased ECF osmolarity)
(5) Blood pressure decreases

Question 27

Why does adrenocortical insufficiency lead decreased ECF osmolarity?

Answer 27

Adrenocortial insufficiency means less aldosterone is produced. Decreased Aldosterone means decreased NaCl reabsorption in the kidneys. This decreases NaCl concentration.