Body Fluid Compartments

Question 1

Renal function

Answer 1

Excretion (urea, blood, nitrogen, creatininate)

Regulation of H2O and electrolyte balance

Regulation of body fluid pH

Regulation of arterial BP (regulation of Na balance…change is change in ECF volume)

Renin-angiotensin-aldosterone system…increase in angiotensin 2…increase i nvasoconstriction.

Increase in aldosterone—-decreased urinary Na excretion

Question 2

Erythrocyte production

Answer 2

Decreased O2 delivery to kidneys…increase EPO…increase erythrocytes

Sites - peritubular fibroblasts and endothelial cells

Regulation - transcription factor - hypoxia inducible factor-1 (HIF-1)

Normal O2 - HIFalpha degraded

Low O2 - HIFa and B dimerize…means increase in EPO trancription and translation

Question 3

Regulation of vitamin D activity

Answer 3

Vitamin D—-25-OH vitamin D (liver)—-1,25(OH)2vitamin D (kidney)

Site - proximal tubule cells via 1 alpha-hydroxylase

Enzyme is very heavily regulated

Question 4

Gluconeogenic capcity

Answer 4

decreased plama glucose…increased renal proximal tubule glucose biosynthesis

Question 5

Metabolic acidosis 
HYperkalemia
Uremic toxicity 
Sodium/H2O imbalance
Ca/PO4 imbalance
PLasma protein imbalance
Anemia 
Immune system

Answer 5

pH<7.4
Plasma K>4
Azotemia - increased plasam creatinine and BUN
Change in fluid volume leads to change in BP
Decreased vitamin D…decreased calcium…increase bone fracterues
Edema - excess fluid deposition in interstitial spsce
Decreased EPO synthesis

Immune - needs to be swimming in ECF environment in order to work properkly

Question 6

Renal functinal reserve capacity

Answer 6

Body homeostasis can be maintained until renal function decreases to 20% of normal

Question 7

Pre-renal failure
Intra-renal failure
Post-renal failure

Answer 7

ARF - reversible

Pre - decreased renal blood flow leads to decreased GFR

Intra- acute tubular necrosis - ischemia./toxin induced

Post - urinary tract obstruction

Question 8

Chronic reanl failure and ESRD

Answer 8

CHronic - irreversible, usually progressive renal injury…most common diabetes

ESRD - GFR<10% of normal

Permenanet renal replacement therapy needed for ESRD but supply

Question 9

Dialysis principle

Answer 9

Across articifical membrane (hemo) or capillaries (peritoneal)

Blood flow through upper compartment…dialysis fluid flows in the counter direction through the lower compartment (renewed)

Question 10

Renal failure dialysis (think K+ and creatinine)

Answer 10

Will have increase plasam creatinine and K+ in renal failure

With lower creatinine/K+ concentrations in the dialysis fluid, both diffuse from plasma to the dialysate

Over the course of the tx period, plasam creatinine, and K+ restored to normal

Question 11

Renail failure dialysis (HCo3-)

Answer 11

Decreased in renal failure (met acid)

With higher concentration in dialysis fluid…will diffuse from dialysate to plasma

Over course of tx, HCO3 returned to normal

Question 12

Renal failure dialysis - fluid accumulation

Answer 12

WIth lower HS pressure and high osmotic pressure in dialysate

Water moves from plasma to dialysate

Over course, EC fluid volume resotred toward normal

Question 13

Hemodialysis

Answer 13

Blood pumped through external artificial dialyzer

3X week for 3-4 hours a piece

Question 14

Peritoneal dialysis

Answer 14

FLuid in peritoneal cavity…peritoneum acts as dialysis memmbranes

Chrnic ambulatory peritoneal dialysis - fluid exchanged 4-6X per day

Higher risk of infection

You can keep doing this yourself

Question 15

Limitation of intermittent hemodialysis

Answer 15

Between sessions - body weight increases due to rentention of water
Plasma creatinine increases

Kidneys “rpcoess” plasam continuously to try to minimize compostion changes

Question 16

Total body water depends on

Answer 16

Gender dependence…higher percentage iin males because of more muslce and less fat

Age - water content decrease with age as muscle decreases and adipose increases

Question 17

Water distribution

Answer 17

2/3 IC and 1/3 EC

ECF - 75% interstitial fluid, 25% plasma, transcelular - 5% of BW

Question 18

Solute content of ECF and ICF

Answer 18

Cations - ECF = Na
ICF = K (due to membrane Na-K-ATPase)

Anions - ECF - Cl-/HCO3-
ICF- organic phaophates and proteins

Question 19

PLasma and interstitual fluid compositions

ECF/ICF osmolarities

Answer 19

Similar except plasma has more protein and therefore more Ca/Mg

ECF and ICF osmolarities are identical

Question 20

How to measure osmolarity

Answer 20

Posm = 2*Na+(glucose/18)+(BUN/2.8)

Question 21

Dilution principle

Answer 21

Add known amount of measurable substance X to unknown volume

Mix until substance distriutes through the fluid

Fluid volume = amount of X added/concentration at equilibrium

Question 22

Application of dilution principle to body fluid volumes

Answer 22

Marker substances distributed in compartments to be measured

Volume should include plasma volume

Any losses quantifiable

SAME marker must be used pre and post tx

Sodiium space/iulin space defines the marker used to measure

Compartment volume = (amount of X given)-amount of X lost divided by conentrationf X at equibilirum

Question 23

ECV
Plasma volume
Total body water

Answer 23

ECV - radiolableed sodium, sucrose, mannitol, inulin

PV - iodinated albumin, T-1824 (evans blue)

Total body water - tritiated water, heavy water, antipyrine

Question 24

Indirect volume measurements (Interstitial volume and intracellular volume)

Answer 24

Cannot take a sample of fluid from volume of interest

Interstitial volume = ECV-PV

ICV = Total body water-ECF

Question 25

Fluid exhcnage between interstitium and intracellular space

Answer 25

Role of osmotic pressure

Disrupted by ingesiton of water, dehydration, IV infusions, fluid losses

To asses impact of an insult…at equilibirium osmolaritires of extra and intra fluid must be equal…shifts result from H2O movememnt ONLY

Question 26

Addition of water

Answer 26

ECF volume increases and as a consequence the ECF osmolarity decreases…H2O flows from ECF to ICF…ECF volume decreases and ICF volume increases and as a consequence the ECF osmolarity increases and ICF osmolarity decreases

Once ECF/ICF osmolarities equalize, there is NO NET flux of H2O

Question 27

Addition of hypertonic NaCl

Hypotonic NaCl

Loss of water

Answer 27

ICV decrease and ECV increase…both osmolarities increase

Both osmolarities decrease and both volumes increase

Both volumes decrease and both osmolarities increase