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96 Cards in this Set
- Front
- Back
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What does the kidney excrete?
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Metabolic waste products and foreign chemicals.
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4 things the kidney regulates:
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1. Water and electrolyte balance
2. Body fluid osmolality and electrolyte concentrations 3. Arterial pressure 4. Acid-base balance |
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What does the kidney do with hormones?
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-Secretion
-Metabolism -Excretion |
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In what important way does the kidney function in metabolism?
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Gluconeogenesis
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What is the central physiologic role of the kidneys?
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Control of the volume and composition of the body fluids.
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What is the nature of normal fluid intake?
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Highly variable
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How does the body keep its fluid volume levels constant?
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By carefully matching the highly variable fluid intake with EQUAL OUTPUT.
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2 major sources from which water is added to the body everyday:
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1. Ingestion via liquids or food
2. Metabolism of carbohydrates |
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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 |
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What is "insensible" water loss?
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Loss through the lungs and skin
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How much is daily insensible water loss normally?
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700 ml/day
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How much do we normally sweat per day?
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100 ml/day
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How much water is normally lost in the feces daily?
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100 ml/day
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How much is daily urine output daily?
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1400 ml/day
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What is the normaly daily output of water?
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2300 - same as normal intake
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How much can daily water output increase during prolonged heavy exercise?
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Up to 6600 ml/day
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Why does water output increase so much during prolonged heavy exercise?
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Because sweating goes up from 100 to 5000 ml
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How much of the body % by weight is water?
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60% - we contain a lot of water.
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How many liters of water are in a 70 kg man if he is 60% water?
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42 L
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Where is the total body water distributed?
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In cells and outside cells
(ICF and ECF) |
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How much of the total body water is inside cells (ICF)? Outside?
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2/3 --> 28 L = ICF
1/2 --> 14 L = ECF |
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What % of body weight by volume is in ECF? ICF?
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ECF = 20%
ICF = 40% |
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What is the barrier between ECF and ICF?
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The cell plasma membrane.
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What are the 2 compartments of the ECF? What fraction is each?
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Interstitial fluid = 3/4
Plasma = 1/4 |
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How much of the ECF is in
-ISF -Plasma |
Total ECF = 14
ISF = 11 Plasma = 3 |
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What is the barrier between the ISF and plasma?
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Capillary walls
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How do you calculate the normal blood volume?
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Plasma vol (3)
------------- = 5 L (1-Hct) (.6) |
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Formula for calculating normal blood volume:
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Plasma volume / 1-Hct
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Can we directly or indirectly measure the different body fluid compartment volumes? How?
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Yes - via the Indicator-dilution method
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What is the basis of the Indicator-dilution method for measuring body fluid volumes?
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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) |
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What body fluid compartments can be measured via the indicator dilution method?
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-Total body water
-Extracellular fluid -Plasma volume |
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What are 3 markers used for measuring total body water?
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-Radioactive water (3H2O)
-Heavy water (2H2O) -Antipyrine |
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What are 5 markers used for measuring ECF?
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-Inulin
-Sucrose -Mannitol -22Na -Thiosulfate |
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What are 2 markers used for measuring Plasma volume?
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-Radiolabeled Albumin
-Evans blue dye |
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What 2 volumes can't be measured directly, but must be calculated?
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-Intracellular volume
-Interstitial volume |
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How is ICF volume calculated?
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TBW - ECF
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How is ISF volume calculated?
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ECF - Plasma
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How is plasma primarily different from ISF?
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Plasma has more proteins
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What are capillary walls permeable to?
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Highly Permeable to: water, electrolytes, and small molecules
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What are capillary walls NOT permeable to?
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Protein
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What are cell membranes permeable to?
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Water
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What are cell membranes not permeable to?
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Proteins and most electrolytes
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What electrolytes are higher in conc in ECF?
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Na, Ca, Cl, and HCO3
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What electrolytes are higher in conc in ICF?
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KPOMP
-K+ -Phosphate -organic anions -Magnesium -protein |
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What is the main important regulator that keeps the ICF and ECF sodium and potassium levels constant?
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Na/K ATPase
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What does Na/K ATPase do?
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Pumps 3 sodiums out per 2 K in for every ATP made.
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To what compartment is water intake added and water output taken from?
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The plasma
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What is the barrier to the distribution of water between the ECF and ICF?
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The cell membrane
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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 |
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5 important concepts that relate to osmotic forces:
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1. Osmolarity
2. Osmotic pressure 3. Osmosis 4. Tonicity 5. Osmotic equilibrium |
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What is the donnan effect?
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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.
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What is osmolarity?
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The total concentration of osmotically active particles in solution
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How are dissolved particles in biological solutions expressed?
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In terms of milliosmoles/L
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What is the osmolarity of 1 L of solution that contains one mole of glucose, urea, or inulin?
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1 Osm/L
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What is the osmolarity of a solution that contains one mole of NaCl?
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2 Osm/L
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What is the average osmolarity of the ECF and ICF in the body?
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280-300 mOsm/L
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How does osmolarity vary within various body compartments?
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It is nearly identical throughout all compartments.
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What is osmolality?
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mOsm/kg water
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Is water osmotically active?
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No; cell membranes are freely permeable to it.
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What is osmotic pressure?
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The force exerted by dissolved osmotically active particles which tends to pull water across semi-permeable membranes.
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What is a semipermeable membrane?
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One that is permeable to water but not to solutes
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What makes a molecule osmotically active?
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It cannot permeate the cell membrane.
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Formula for calculating osmotic pressure:
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osmotic pressure = CRT
C = concentration R = constant T = 37 degrees |
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How do you calculate osmotic pressure at 37 degrees?
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Osmotic pressure = 19.3 x Osmolarity
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If plasma's normal osmolarity is 282 mOsm/L, what is the osmotic pressure of plasma?
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5443 mm Hg
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Define osmosis:
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The movement of water across a semi-permeable membrane due to differences in osmolarity
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What is tonicity?
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A term that describes how a solution influences a cell's volume.
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What is an isotonic solution?
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One that does not change cell volume
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What is a hypertonic solution?
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One that will cause a cell volume to shrink
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What is a hypotonic solution?
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One that will cause a cell volume to swell
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What is the goal of the body and renal regulation of ECF?
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To maintain an isotonic solution that is in equilibrium with the cell.
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Whereas osmotic pressure governs fluid movement across cell membranes, what governs that at capillaries?
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Starling's forces
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What are Starling's forces?
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-Capillary hydrostatic pressure
-Capillary oncotic pressure -ISF hydrostatic pressure -ISF oncotic pressure |
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Equation for flux across a capillary membrane:
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Flux = Kf (Forces out - F in)
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What are the forces directed out of the capillary?
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Phydrostatic + IF oncotic pressure
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What are the forces directed in at the capillary?
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IF hydrostatic pressure + capillary oncotic pressure
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What is the net force generally at capillaries?
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Slightly favoring outward filtration.
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What happens to the net fluid filtered at capillaries?
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It is collected as lymph and returned to the circulation.
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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 |
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Why won't ICF change when you give isotonic salt water?
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Because all the salt stays in the plasma but there's no force to pull it into cells.
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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 |
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Why does ICF volume decrease when you give hypertonic NaCl solution?
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Because water goes out of cells to where the more solute is.
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What will giving Hypotonic NaCL do to the following:
-Total body water -Extracellular fluid water -Intracellular fluid water |
TBW: Increase
ECF: Increase ICF: Increase |
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Define hypernatremia
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Elevated plasma NA concentration about 150 mEq/L
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Define hyponatremia
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Decreased plasma Na concentration below 135 mEq/L
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Define Hyperkalemia
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Elevated plasma K above 5
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Define Hypokalemia
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Decreased plasma K below 3.5
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Define hypercalcemia
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Elevated plasma Ca above 10 mg/dl
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Define hypocalcemia
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Decreased plasma Ca below 8 mg/dl
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Define Acidosis
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REduced plasma pH below 7.3
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Define Alkalosis
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Elevated plasma pH above 7.5
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What is Edema?
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Excess fluid in the tissues
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What are 2 types of edema?
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-intrcellular
-extracellular |
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what causes intracellular edema?
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Insufficient Na/K atpase so that swelling of cells occurs
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What causes extracellular edema?
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Increased capillary filtration
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3 causes of extracellular edema:
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1. Elevated venous pressure (heart failure)
2. Loss of plasma protein (cirrhosis of liver, nephrotic syndrome) 3. Lymphatic blockage |
