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96 Cards in this Set

  • Front
  • Back
What does the kidney excrete?
Metabolic waste products and foreign chemicals.
4 things the kidney regulates:
1. Water and electrolyte balance
2. Body fluid osmolality and electrolyte concentrations
3. Arterial pressure
4. Acid-base balance
What does the kidney do with hormones?
In what important way does the kidney function in metabolism?
What is the central physiologic role of the kidneys?
Control of the volume and composition of the body fluids.
What is the nature of normal fluid intake?
Highly variable
How does the body keep its fluid volume levels constant?
By carefully matching the highly variable fluid intake with EQUAL OUTPUT.
2 major sources from which water is added to the body everyday:
1. Ingestion via liquids or food
2. Metabolism of carbohydrates
How much H2O do we ingest daily?
How much do we make w/ metabsm? What is daily normal water intake?
-Ingest 2100
-Make 200
Total water intake ~2300 ml/day
What is "insensible" water loss?
Loss through the lungs and skin
How much is daily insensible water loss normally?
700 ml/day
How much do we normally sweat per day?
100 ml/day
How much water is normally lost in the feces daily?
100 ml/day
How much is daily urine output daily?
1400 ml/day
What is the normaly daily output of water?
2300 - same as normal intake
How much can daily water output increase during prolonged heavy exercise?
Up to 6600 ml/day
Why does water output increase so much during prolonged heavy exercise?
Because sweating goes up from 100 to 5000 ml
How much of the body % by weight is water?
60% - we contain a lot of water.
How many liters of water are in a 70 kg man if he is 60% water?
42 L
Where is the total body water distributed?
In cells and outside cells
(ICF and ECF)
How much of the total body water is inside cells (ICF)? Outside?
2/3 --> 28 L = ICF
1/2 --> 14 L = ECF
What % of body weight by volume is in ECF? ICF?
ECF = 20%
ICF = 40%
What is the barrier between ECF and ICF?
The cell plasma membrane.
What are the 2 compartments of the ECF? What fraction is each?
Interstitial fluid = 3/4
Plasma = 1/4
How much of the ECF is in
Total ECF = 14
ISF = 11
Plasma = 3
What is the barrier between the ISF and plasma?
Capillary walls
How do you calculate the normal blood volume?
Plasma vol (3)
------------- = 5 L
(1-Hct) (.6)
Formula for calculating normal blood volume:
Plasma volume / 1-Hct
Can we directly or indirectly measure the different body fluid compartment volumes? How?
Yes - via the Indicator-dilution method
What is the basis of the Indicator-dilution method for measuring body fluid volumes?
C1V1 = C2V2
-you know the concentration and volume that you inject, then you measure the final concentration after equilibrium. Allows you to then calculate volume (subtract the vol added)
What body fluid compartments can be measured via the indicator dilution method?
-Total body water
-Extracellular fluid
-Plasma volume
What are 3 markers used for measuring total body water?
-Radioactive water (3H2O)
-Heavy water (2H2O)
What are 5 markers used for measuring ECF?
What are 2 markers used for measuring Plasma volume?
-Radiolabeled Albumin
-Evans blue dye
What 2 volumes can't be measured directly, but must be calculated?
-Intracellular volume
-Interstitial volume
How is ICF volume calculated?
How is ISF volume calculated?
ECF - Plasma
How is plasma primarily different from ISF?
Plasma has more proteins
What are capillary walls permeable to?
Highly Permeable to: water, electrolytes, and small molecules
What are capillary walls NOT permeable to?
What are cell membranes permeable to?
What are cell membranes not permeable to?
Proteins and most electrolytes
What electrolytes are higher in conc in ECF?
Na, Ca, Cl, and HCO3
What electrolytes are higher in conc in ICF?
-organic anions
What is the main important regulator that keeps the ICF and ECF sodium and potassium levels constant?
Na/K ATPase
What does Na/K ATPase do?
Pumps 3 sodiums out per 2 K in for every ATP made.
To what compartment is water intake added and water output taken from?
The plasma
What is the barrier to the distribution of water between the ECF and ICF?
The cell membrane
What governs the distribution of water between the ECF and ICF?
What governs the distribution of water between the plasma and ISF?
-Osmotic forces

-Starling forces
5 important concepts that relate to osmotic forces:
1. Osmolarity
2. Osmotic pressure
3. Osmosis
4. Tonicity
5. Osmotic equilibrium
What is the donnan effect?
The effect of having more negatively charged proteins in plasma which attract Na and K so the cation concentrations are slightly higher in plasma than in ISF.
What is osmolarity?
The total concentration of osmotically active particles in solution
How are dissolved particles in biological solutions expressed?
In terms of milliosmoles/L
What is the osmolarity of 1 L of solution that contains one mole of glucose, urea, or inulin?
1 Osm/L
What is the osmolarity of a solution that contains one mole of NaCl?
2 Osm/L
What is the average osmolarity of the ECF and ICF in the body?
280-300 mOsm/L
How does osmolarity vary within various body compartments?
It is nearly identical throughout all compartments.
What is osmolality?
mOsm/kg water
Is water osmotically active?
No; cell membranes are freely permeable to it.
What is osmotic pressure?
The force exerted by dissolved osmotically active particles which tends to pull water across semi-permeable membranes.
What is a semipermeable membrane?
One that is permeable to water but not to solutes
What makes a molecule osmotically active?
It cannot permeate the cell membrane.
Formula for calculating osmotic pressure:
osmotic pressure = CRT

C = concentration
R = constant
T = 37 degrees
How do you calculate osmotic pressure at 37 degrees?
Osmotic pressure = 19.3 x Osmolarity
If plasma's normal osmolarity is 282 mOsm/L, what is the osmotic pressure of plasma?
5443 mm Hg
Define osmosis:
The movement of water across a semi-permeable membrane due to differences in osmolarity
What is tonicity?
A term that describes how a solution influences a cell's volume.
What is an isotonic solution?
One that does not change cell volume
What is a hypertonic solution?
One that will cause a cell volume to shrink
What is a hypotonic solution?
One that will cause a cell volume to swell
What is the goal of the body and renal regulation of ECF?
To maintain an isotonic solution that is in equilibrium with the cell.
Whereas osmotic pressure governs fluid movement across cell membranes, what governs that at capillaries?
Starling's forces
What are Starling's forces?
-Capillary hydrostatic pressure
-Capillary oncotic pressure
-ISF hydrostatic pressure
-ISF oncotic pressure
Equation for flux across a capillary membrane:
Flux = Kf (Forces out - F in)
What are the forces directed out of the capillary?
Phydrostatic + IF oncotic pressure
What are the forces directed in at the capillary?
IF hydrostatic pressure + capillary oncotic pressure
What is the net force generally at capillaries?
Slightly favoring outward filtration.
What happens to the net fluid filtered at capillaries?
It is collected as lymph and returned to the circulation.
What will giving Isotonic NaCL do to the following:
-Total body water
-Extracellular fluid water
-Intracellular fluid water
TBW: increased
ECF: increased
ICF: no change
Why won't ICF change when you give isotonic salt water?
Because all the salt stays in the plasma but there's no force to pull it into cells.
What will giving Hypertonic NaCL do to the following:
-Total body water
-Extracellular fluid water
-Intracellular fluid water
-TBW will increase
-ECF will increase
-ICF will decrease
Why does ICF volume decrease when you give hypertonic NaCl solution?
Because water goes out of cells to where the more solute is.
What will giving Hypotonic NaCL do to the following:
-Total body water
-Extracellular fluid water
-Intracellular fluid water
TBW: Increase
ECF: Increase
ICF: Increase
Define hypernatremia
Elevated plasma NA concentration about 150 mEq/L
Define hyponatremia
Decreased plasma Na concentration below 135 mEq/L
Define Hyperkalemia
Elevated plasma K above 5
Define Hypokalemia
Decreased plasma K below 3.5
Define hypercalcemia
Elevated plasma Ca above 10 mg/dl
Define hypocalcemia
Decreased plasma Ca below 8 mg/dl
Define Acidosis
REduced plasma pH below 7.3
Define Alkalosis
Elevated plasma pH above 7.5
What is Edema?
Excess fluid in the tissues
What are 2 types of edema?
what causes intracellular edema?
Insufficient Na/K atpase so that swelling of cells occurs
What causes extracellular edema?
Increased capillary filtration
3 causes of extracellular edema:
1. Elevated venous pressure (heart failure)
2. Loss of plasma protein (cirrhosis of liver, nephrotic syndrome)
3. Lymphatic blockage