bodily fluid control (midterm 3)

Question 1

what do the kidneys do

Answer 1

maintain bodily fluid volumes and compositions

Question 2

how much water does a 70 kg person contain

Answer 2

42 liters of water (60%) (Vt)

Question 3

how many liters of water are inside the 75 trillion cells of the body and what are they part of

Answer 3

28 liters - intracellular fluid (Vic)

Question 4

how many liters of water are extracellular

Answer 4

14 - 11 are interstitial (Vis), 3 are plasma (Vp)

Question 5

how many liters of water are blood and how many are plasma

Answer 5

5 liters; 3 liters

Question 6

how do you measure total body water

Answer 6

add a bolus of radioactive water and measure concentration after a few hours (Vt)

Question 7

how do you measure extracellular fluid volume

Answer 7

add a bolus of radioactive sodium and measure concentration after a few hours (Vec)

Question 8

how do you measure intracellular fluid volume

Answer 8

equals total body water minus extracellular fluid volume (Vic)

Question 9

how do you measure plasma volume

Answer 9

add a bolus of radioactive serum albumin and measure concentration after a few hours (Vp)

Question 10

how do you measure interstitial fluid volume

Answer 10

equals extracellular fluid volume minus plasma volume (Vis)

Question 11

how do you measure total blood volume

Answer 11

plasma volume / (1 minus hematocrit)
hematocrit = total blood cell volume

Question 12

what is osmosis

Answer 12

the diffusion of water, through a selectively permeable membrane, from a region of low solute concentration to high solute concentration

Question 13

why does osmosis happen

Answer 13

water moves to try to equilibrate solute concentration on either side of the membrane

Question 14

what is an osmole

Answer 14

the total number of particles in solution that are establishing an osmotic gradient
= moles x dissociable particles

Question 15

what is the normal value for osmoles

Answer 15

280 mOsm/L
dominated by Na+, glucose, urea

Question 16

what is osmosis equilibrium

Answer 16

if a cell is placed in a solution with normal osmolarity (280 mOsm/L) the cell will neither shrink or swell - isotonic solution

Question 17

what is a hypotonic solution vs hypertonic solution

Answer 17

solution with less osmolarity vs solution with more osmolarity

Question 18

what does a hypotonic solution result in

Answer 18

the cell will swell as it tries to dilute its solutes

Question 19

what does a hypertonic solution result in

Answer 19

the cell will shrink as it tries to concentrate its solutes

Question 20

what two basic principles guide the discussion of fluid regulation

Answer 20

1. intracellular = extracellular osmolarity due to water transport across membrane
2. total osmolarity of a system (intracellular + extracellular) is constant unless added or removed

Question 21

if a hypertonic solution is administered to a patient, what happens?

Answer 21

• The osmolarity of the extracellular fluid increases, intracellular decreases
• Osmosis pushes water out of the cell and into the extracellular space

Question 22

if a hypotonic solution is administered to a patient, what happens?

Answer 22

• The osmolarity of the extracellular fluid decreases, intracellular increases
• Osmosis pushed water into the cell and out of the extracellular space

Question 23

what is an edema

Answer 23

the presence of excess fluid in the body, typically in the extracellular fluid space but sometimes involving the intracellular fluid space

Question 24

what two conditions lead to an intracellular edema and how common are they

Answer 24

RARE
- Depression of metabolic systems of the tissues
- Inadequate nutrient delivery to the cell

Question 25

what two conditions lead to an extracellular edema and how common are they

Answer 25

COMMON
- Abnormal leakage of fluid from the plasma through the capillary wall and into the interstitial space
- failed lymphatic drainage

Question 26

what is the equation that describes capillary filtration and what does each variable stand for

Answer 26

Filtration = Kf x (Pc - Pif - πc + πif)
- Kf = capillary filtration coefficient
- Pc = capillary hydrostatic pressure
- Pif = interstitial fluid hydrostatic pressure
- πc = capillary osmotic pressure
- πif = interstitial osmotic pressure

Question 27

what increases capillary filtration

Answer 27

increased Kf, increased Pc, decreased πc

Question 28

what results in heart failure

Answer 28

decreased cardiac output, increased capillary pressure leads to increased capillary filtration

Question 29

what results in renal failure

Answer 29

decreased Na+/H2O excretion, increased blood volume, increased arterial pressure, increased Pc leads to increased capillary filtration

Question 30

what three safety factors prevent an edema

Answer 30

• increased interstitial fluid volume will lead to increased interstitial fluid pressure
• the ability of the lymph flow to increase 10-50 fold
• washdown of interstitial fluid protein