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CRR > L23 - Fluid compartments of the body and their composition > Flashcards

L23 - Fluid compartments of the body and their composition Flashcards

1
Q

What is 1 litre of water equivalent to in mass?

A

1 litre of water = 1kg of body mass

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2
Q

Which conditions occur when there is an excess of body fluid? (due to an inability to regulate water balance)

A

1) Pulmonary Oedema - swellings in the pulmonary vasculature. This stops you from doing efficient gas exchange.
2) Peripheral Oedema - e.g. swelling of the ankles due to gravity. This reduced your mobility, which means you exercise less which encourages oedema.

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3
Q

What are the conditions which occur when there is too little fluid?

A

1) Dizziness - due to dehydration (because you are not able to perfuse your brain properly)
2) Hypovolemic Shock - not being able to maintain perfusion of organs affects the kidneys and brains.

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4
Q

For the standard male, what is % of body weight which is water?

A

60% of body weight is water. E.g. for a 70kg male = 42 litres is the total body water (0.6 x 70 = 42)

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5
Q

For the standard female, what is the % of body weight which is water?

A

50% of body weight is water for women.

e.g. 70kg women = 35 litres total body water

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6
Q

Why is there a difference in the total body water of men and women?

A

1) Men have more muscle tissue - which contains water.

2) Women have more adipose tissue as a proportion of body weight.

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7
Q

What is the water content of adipose tissue?

A

Adipose water content - 10-15%.

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8
Q

What is adipose tissue responsible for?

A

Adipose content is responsible for TBW (total body weight) variation between individuals.

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9
Q

If the adipose tissue of an individual increase, does the total body weight increase?

A

No, as your weight increases, there is an increase in the adipose tissue which means that the body water doesn’t increase in the same proportion.

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10
Q

How is the total body weight divided?

A

The total body weight is divided into compartments. Compartment = a small space or subdivision for storage.

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11
Q

How is the body fluid divided into compartments?

A

Body fluid is divided into:

a) Extracellular Fluid (35% = 1/3)
b) Intracellular Fluid (65% = 2/3)

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12
Q

What is the extracellular fluid further divided into?

A

a) Interstitial Fluid = 25%
b) Plasma fluid = 8%
c) Transcellular fluid= 2%

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13
Q

What is the intracellular fluid (ICF) compartment?

A

It is virtual compartment that is made up of millions of cells. Fluid contained within cells.

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14
Q

What are the features of the ICF compartment?

A

1) The fluid is contained within the cell membrane of the cells (within the cytoplasm)
2) Potassium is the major cation contained within the ICF (K+ is much higher inside the cell and lower outside the cell)
3) Proteins and phosphates are the major anions contained within the ICF.

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15
Q

What is the extracellular (ECF) compartment?

A

Any non-intracellular fluid = therefore, as it not one single compartment. It consists of the fluid that bathes the cells (outside the cells).

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16
Q

What are the features of the extracellular fluid?

A

1) Na+ ions are the major cation (within the ECF) - so sodium is present in the fluid which surrounds the cells.
2) Chloride and bicarbonate are the major anions (present in fluid outside of the cells).

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17
Q

What is the plasma fluid (of the ECF)? How much of the plasma fluid is composed of proteins and lipid? How much of the plasma fluid is actual fluid?

A

Plasma fluid = a type of (ECF) fluid contained within the vasculature.
70ml per litre of plasma is composed of protein and lipid (1 litre = 930ml)
70ml = of plasma fluid is composed of proteins and lipid.

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18
Q

What is the interstitial fluid? (of ECF)

A

The interstitial is the fluid present in the interstitial space (present outside of the capillaries, bathing the cells).

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19
Q

How is the plasma fluid and the interstitial fluid separated?

A

The ISF is separated from the plasma fluid by the capillary endothelium.

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20
Q

What is the function of the interstitial fluid?

A

ICF acts as a link between the intracellular fluid and the blood plasma (plasma fluid).

E.g. substances diffuse out of the blood plasma into the interstitial fluid and then into the plasma fluid.

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21
Q

Describe the protein content of the ISF

A

ISF is low in protein.

22
Q

How is excess ISF drained/removed?

A

Excess ISF drains into the plasma fluid compartment via lymphatic system (returned back to the venous system & is important in immunology)

23
Q

What is the transcellular fluid (TCF)?

A

The fluid that is separate from the extracellular fluid.

24
Q

How is the TCF separated from the plasma?

A

The TCF is separated from the plasma by an additional epithelial layer.

25
Q

Examples of TCF and where the TCF is present?

A

1) Urine - in the bladder.
2) CSF - clear fluid that bathes meninges and brain/separate.
3) Lymph - drainage of interstitial fluid and mediates immune reactions.
4) GI Tract content and secretion.
5) Synovial Fluid - in the joints.
6) Compartment of the eye and ear.

26
Q

How do you measure the volumes of the fluid compartment?

A

Using the dilution principle to calculate the:

Compartment Volume (V = ml) = Quantity of Dye (mg) / Concentration of Dye (mg/ml)

  • where the mass of the dye is known.
  • the concentration of the solution is calculated.
27
Q

Describes the process of calculating of the compartment volume.

A

1) Add a dye (with a known mass) to an unknown volume of compartment fluid.
2) Use colorimetry to calculate the concentration of the tracer/dye solution (shining light through the dye solution and using the intensity of the solution to find concentration - extrapolation)
3) Compartment Volume = Mass of Dye (mg) / Concentration of Dye (mg/ml)

28
Q

What assumptions are made when calculating the compartment volume?

A

1) Assumes that the distribution of the dye is equal across the whole fluid compartment (e.g. however, for plasma fluid, the dye could bind to the proteins in the fluid = reduced distribution). So you may not get an accurate concentration.
2) Assumes that there is no excretion of the dye.

29
Q

What is osmolality?

A

Number of osmoles (particles) of solute per kilogram of H20.

30
Q

What is the formula for osmolality?

A

Osmolality (mosmol/kg H2O) =
n x molar concentration (mmol/kg H2O)

n = number of ions a substance dissociates into.

31
Q

How do you work out the osmolality of non-dissociating substances?

A

For non-dissociating substances:

n = identical to the number of moles.

E.g. for Glucose
Osmolality = 1x1 = 1

32
Q

How do you work out the osmolality of the dissociating substances?

A

The molar concentration is multiplied by the ions in dissociation (n) .
n = no. of ions in dissociation

E.g. NaCL = dissociates into Na+ and Cl- in solution.

Molar conc = 1
N = 2

So, osmolality = 2

33
Q

What is the body fluid osmolality? Which organ regulates this?

A

The kidneys keep the body fluid osmolality at around 180-300 mosmol/kg H2O.

34
Q

Is there a difference between the osmolality of ICF compared to ECF? Why?

A

No, ICF and ECF osmolalities are identical because H2O can readily cross cell membranes

35
Q

Which protein channels are used to transport water across cell membranes?

A

Aquaporins (membrane bound water channels)

36
Q

What is Hydrostatic Pressure? What does it depend on?

A

The pressure exerted by a fluid on the walls of a compartment. It’s dependent on the size of the compartment and the volume of the fluid.

37
Q

What is osmotic pressure?

A

The pressure required to prevent the net movement of water across a semi-permeable membrane (the pressure required to prevent the movement of water through a semi-permeable membrane via diffusion)

38
Q

What is an isotonic solution?

A

A solution which doesn’t cause changes in cell volume. (a solution which contains an osmole which doesn’t move into a cell). E.g. RBC - don’t undergo haemolytic in isotonic solution.

39
Q

What are isosmotic solutions?

A

Solutions which have the same osmolality.

40
Q

Can a solution be both isotonic and isosmotic?

A

1) Isotonic solutions are always isosmotic (they have the same osmolality = cell doesn’t expand)
2) Isosmotic solutions may not be isotonic (because they could cause changes in cell volume)

41
Q

Give an example of an isosmotic solutions which isn’t isotonic?

A

RBC’s in isosmotic Urea.

Urea readily diffuses and equilibrates across the cell membrane & cancels it’s own osmotic

42
Q

What are effective osmoles?

A

Effective osmoles are impermeant and so encourage net water movement through the membrane by exerting an osmotic pressure (e.g. plasma proteins) - (unable to diffuse so cause an osmotic pressure)

43
Q

What are ineffective osmoles?

A

Ineffective osmoles will diffuse readily across membrane cancelling their own osmotic pressure (e.g. urea).

44
Q

What is plasma protein oncotic (colloid) pressure?

A

Osmotic pressure exerted by plasma proteins (which are large impermeant anions). They are represented by pie.

45
Q

What is the equation for the Gibbs-Donnan effect?

A

Diffusible Cations (side 1) x Diffusible Anions (side 1) = Diffusible Cations (side 2) x Diffusible Anions (side 2)

46
Q

What happens to each side of the membrane if side 1 contains non-diffusible proteins?

A

1) There will be more ions present in side 1 than side 2

2) Side 1 contains non-diffusible ions (which are impermeant) = so side 1 exerts a greater osmotic pressure.

47
Q

What is bulk flow?

A

Passive solute movement which occurs in vessels. It also occurs in the form of filtration (and reabsorption) across capillary membranes.

48
Q

What are starling forces?

A

The forces that determine capillary filtration and reabsorption. i.e. the movement of water and solutes between plasma compartments and ISF compartments.

49
Q

What does starling forces consist of?

A

1) Capillary hydrostatic pressure
2) Plasma protein oncotic pressure
3) Hydrostatic pressure outside the capillary.
-

50
Q

What proportion of movement across the capillary membrane do the Starling forces make up?

A

10% (other 90% is diffusion across membrane)

51
Q

What does hydrostatic pressure depend on?

A

1) Arterial blood pressure
2) Extend of Transmittion (i.e. arteriolar resistance?
3) Venous Pressure (resistance to flow)

52
Q

What is plasma protein oncotic pressure?

A

Pressure exerted by the plasma proteins which are impermeant.
The pressure is at a constant 25mmHg = plasma proteins always impermeant = always exert this pressure.

CRR (3 decks)

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