Body Fluid Composition & Osmolarity

Question 1

What are the percentages of intracellular and extracellular fluid that compose the 60% humans have of total body water?

Answer 1

ICF is 40%, ECF is 20%

Question 2

What does extracellular fluid entail (what other “fluids” are grouped under it)?

Answer 2

It includes the interstitial fluid bathing cells and the blood plasma within the vascular
system. + (as well as transcellular fluid)

Question 3

What is fluid balance?

Answer 3

The distribution of water in the body

Question 4

How is fluid balance maintained?

Answer 4

It is maintanted throuhg a balance between the intake and the output of water. It can only be maintaned it intake equals output

Question 5

Which is the primary body system where humans intake water?

Answer 5

Gastrointestinal

Question 6

Through which body systems humans have water output?

Answer 6

Intergumentary (skin), Urinary system, Gastrointestinal, Respiratory (lungs - watre vapour)

Question 7

What are the two vital functions of extracellular body fluid?

Answer 7

Maintains a constant environment for cells and allows the transportation of materials to and from cells

Question 8

Which has a higher clinical relevance, intracellular or extracellular body fluid? Why?

Answer 8

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.

Question 9

How is ICF (intracellular) and ECF (extracellular) kept separated in the body? What about interstitial fluid and plasma?

Answer 9

ICF is separated from ECF by the cell membranes. Interstitial fluid is separated
from plasma by capillary endothelia

Question 10

What is transcellular fluid? Example

Answer 10

It is extrecellular fluid, which is separated from the interstitial compartment by cell membranes of specialized tissue. Some examples are cerebrospinal and extraocular fluids

Question 11

How do the concentration of Na+ and K+ concentrations vary in ICF and ECF?

Answer 11

ICF has low Na+ and high K+. ECF has high Na+ and low K+. Think about the sodium potassium pump –> 3Na+ out 2K+ in

Question 12

What is fluid homeostasis?

Answer 12

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.

Question 13

What is osmolality and osmolarity? What is the difference?

Answer 13

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.

Question 14

What cells are particularly at risk when alterations in fluid homeostasis occur?

Answer 14

Neurons

Question 15

Is osmolarity always reliable?

Answer 15

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.

Question 16

What solutes are taken into account when calculating osmolarity?

Answer 16

It is derived from the measured Na+, K+, urea and
glucose concentrations.

Question 17

How is osmolality measured in clinical laboratories?

Answer 17

Using an osmometer

Question 18

What is osmosis?

Answer 18

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.

Question 19

What are isotonic hypertonic and hypotonic solutions?

Answer 19

Isnotonic has the same concentration as the cytoplasm, hypertonic is more concnetrated, hypotonic is less concentrated

Question 20

What are the respective effects on cells on isotonic, hypertonic and hypotonic solutions?

Answer 20

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)

Question 21

What is an osmole?

Answer 21

1 mole of any fully dissociated substance in water

Question 22

What is an electrolyte?

Answer 22

Is a compund that will dissoacite into charged ions when placed in a solution

Question 23

Name four important cations and four important anions that partake in nutrient or regulatory roles.

Answer 23

Cations: Na+ (sodium), K+ (potassium), Ca++ (calcium), Mg++ (magnesium)
Anions: Cl- (chloride), HCO3- (bicarbonate), HPO4- (phospahte) and negatively charged proteins

Question 24

Name six factors that can cause ECF volumes to change markedly

Answer 24

Ingestion of water, dehydration, intravenous infusion (f many different solution), diarrhea, vomiting, lsing abnormal amounts of fluid from the gastrointenstinal tract, sweating, exessive urination

Question 25

What is volume contraction?

Answer 25

Decrease in ECF

Question 26

What is volume expansion?

Answer 26

Increase in ECF

Question 27

What do terms such as isosmotic, hyperosmotic and hyposmotic refer to?

Answer 27

Refer to the osmolarity of the ECF

Question 28

Why is plasma sodium concentration a reasonable indicator of plasma osmolarity under many conditions?

Answer 28

Because sodium and its associated ions (mainly chloride) account for 90% of the solutes in the ECF

Question 29

What is hyponatremia?

Answer 29

Lower than normal plasma sodium concentration

Question 30

What is hypernatremia?

Answer 30

HIgher than normal plasma sodium concentration

Question 31

What is the normal plasma sodium concentration?

Answer 31

Around 142 mEq/L

Question 32

What are two things that can result in hyponatremia?

Answer 32

Loss of sodium from the ECF or gain of excess water to the ECF

Question 33

What does a primary loss of sodium usually result in? What two conditions can lead to the loss of sodium?

Answer 33

Hyponaetremia and dehydration. Vomiting and diarrhea can lead to it.

Question 34

How does the overuse of diuretics may end in hyponatremia?

Answer 34

It can inhibit the ability of the kidneys to conserve sodium leading to hyponaetremia

Question 35

What is Addison disease? How can it lead to a modest degree of hyponatremia?

Answer 35

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

Question 36

What occurs with brain tissue during acute hyponatremia? Why?

Answer 36

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.

Question 37

What is the difference in regards to ECF and ICFwhen a patient presents with hyponatremia and dehydration vs hyponatremia and overhydration?

Answer 37

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.

Question 38

What are two causes of hyponatremia+overhydration? Explain one

Answer 38

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.

Question 39

Why are hypokalemia and hyperkalemia particularly dangerous?

Answer 39

Because potassium affects the contractility of the heart muscle

Question 40

What is hypokalemia and hyperkalemia?

Answer 40

Hypokalemia is a lower than normal serum potassium concentration, Hyperkalemia is a higher han normal serum potassium concentration