Body Fluid Composition & Osmolarity Flashcards
What are the percentages of intracellular and extracellular fluid that compose the 60% humans have of total body water?
ICF is 40%, ECF is 20%
What does extracellular fluid entail (what other “fluids” are grouped under it)?
It includes the interstitial fluid bathing cells and the blood plasma within the vascular
system. + (as well as transcellular fluid)
What is fluid balance?
The distribution of water in the body
How is fluid balance maintained?
It is maintanted throuhg a balance between the intake and the output of water. It can only be maintaned it intake equals output
Which is the primary body system where humans intake water?
Gastrointestinal
Through which body systems humans have water output?
Intergumentary (skin), Urinary system, Gastrointestinal, Respiratory (lungs - watre vapour)
What are the two vital functions of extracellular body fluid?
Maintains a constant environment for cells and allows the transportation of materials to and from cells
Which has a higher clinical relevance, intracellular or extracellular body fluid? Why?
Extracellular, because it is the one which is measured clinically, through blood samples. The electrolyte levels from ECF in the blood or in the blood serum are what is measured.
How is ICF (intracellular) and ECF (extracellular) kept separated in the body? What about interstitial fluid and plasma?
ICF is separated from ECF by the cell membranes. Interstitial fluid is separated
from plasma by capillary endothelia
What is transcellular fluid? Example
It is extrecellular fluid, which is separated from the interstitial compartment by cell membranes of specialized tissue. Some examples are cerebrospinal and extraocular fluids
How do the concentration of Na+ and K+ concentrations vary in ICF and ECF?
ICF has low Na+ and high K+. ECF has high Na+ and low K+. Think about the sodium potassium pump –> 3Na+ out 2K+ in
What is fluid homeostasis?
Maintaining stable total body water and total salt content. A decrese/ increase in water and salt intake results in a equivalent change in renal water and salt excretion to maintain the balance.
What is osmolality and osmolarity? What is the difference?
Both are measures os solute per quantity of solution. Osmolarity is number of particles per liter of the solution, whereas osmolality is number f particles per kilogram of solvent.
What cells are particularly at risk when alterations in fluid homeostasis occur?
Neurons
Is osmolarity always reliable?
No. SInce it is measured based on gluscose, urea, Na+ and K+ concentrations, when looking at conditions such as hyperlipedemia (where lipids are the issue) osmolarty is not always reliable.
What solutes are taken into account when calculating osmolarity?
It is derived from the measured Na+, K+, urea and
glucose concentrations.
How is osmolality measured in clinical laboratories?
Using an osmometer
What is osmosis?
Is the net diffusion of water across a selectively permeable mebrane from a region of high water potential to a region of low water potential.
What are isotonic hypertonic and hypotonic solutions?
Isnotonic has the same concentration as the cytoplasm, hypertonic is more concnetrated, hypotonic is less concentrated
What are the respective effects on cells on isotonic, hypertonic and hypotonic solutions?
Isotonic (normal), hypertonic (more water leave th ecell and go into the hypertonic solution - cell will lose water), hypotonic (more water will go from the hypotonic solution into the cell, causing it to expand)
What is an osmole?
1 mole of any fully dissociated substance in water
What is an electrolyte?
Is a compund that will dissoacite into charged ions when placed in a solution
Name four important cations and four important anions that partake in nutrient or regulatory roles.
Cations: Na+ (sodium), K+ (potassium), Ca++ (calcium), Mg++ (magnesium)
Anions: Cl- (chloride), HCO3- (bicarbonate), HPO4- (phospahte) and negatively charged proteins
Name six factors that can cause ECF volumes to change markedly
Ingestion of water, dehydration, intravenous infusion (f many different solution), diarrhea, vomiting, lsing abnormal amounts of fluid from the gastrointenstinal tract, sweating, exessive urination
What is volume contraction?
Decrease in ECF
What is volume expansion?
Increase in ECF
What do terms such as isosmotic, hyperosmotic and hyposmotic refer to?
Refer to the osmolarity of the ECF
Why is plasma sodium concentration a reasonable indicator of plasma osmolarity under many conditions?
Because sodium and its associated ions (mainly chloride) account for 90% of the solutes in the ECF
What is hyponatremia?
Lower than normal plasma sodium concentration
What is hypernatremia?
HIgher than normal plasma sodium concentration
What is the normal plasma sodium concentration?
Around 142 mEq/L
What are two things that can result in hyponatremia?
Loss of sodium from the ECF or gain of excess water to the ECF
What does a primary loss of sodium usually result in? What two conditions can lead to the loss of sodium?
Hyponaetremia and dehydration. Vomiting and diarrhea can lead to it.
How does the overuse of diuretics may end in hyponatremia?
It can inhibit the ability of the kidneys to conserve sodium leading to hyponaetremia
What is Addison disease? How can it lead to a modest degree of hyponatremia?
Addison disease is a disease that results from a decrease in the secretion of adolsterone. The diease impairs the kidneys ability to reabsorb sodium thus being able to lead to modest hyponaetremia
What occurs with brain tissue during acute hyponatremia? Why?
The brain tissues swells, because hyponaetremia is caused either by loss of Na+ or gain of water, either way the solutions around the brain become hypotonic, causing water to move into the brain cells through osmosis, leading to the swelling.
What is the difference in regards to ECF and ICFwhen a patient presents with hyponatremia and dehydration vs hyponatremia and overhydration?
ECF if a patient with hyponaetremia + dehydration will have a reduced volume, while the one of a patient with hyponaetremia,but overhydration, will have an increased volume. In the case of the ICF, in both cases ICF volume will increase, as the ECF will become less concentrated (hypotonic) leading to more water going into the cells.
What are two causes of hyponatremia+overhydration? Explain one
Excess ADH and bronchogenic tumors. IN regards to ADH, more ADH, will lead to a more concentrated urine, thus more water is reabsorbed into the body, causing overhydration. The excess water in the ECF then impacts the ECFs concentration (more water for the same amount of sodium, means sodium is less concentrated), leading to hyponaetremia.
Why are hypokalemia and hyperkalemia particularly dangerous?
Because potassium affects the contractility of the heart muscle
What is hypokalemia and hyperkalemia?
Hypokalemia is a lower than normal serum potassium concentration, Hyperkalemia is a higher han normal serum potassium concentration
