L3 Water, Fluids, Spaces and Compartments

Question 1

Only regulated route for the excretion of fluid from the body?

Answer 1

The only regulated route for excretion of water from the body is the kidneys; urine volume can vary from 0.5 to 18L/day.

Question 2

Estimation of fluid volumes in various body compartments based on weight?

Answer 2

Question 3

What is the blood volume of an individual with 3.5L plasma and 40% Hct?

Answer 3

Question 4

How does the kidney regulate water
excretion?

Answer 4

Late distal tubules and collecting tubules of kidney nephrons express numerous aquaporins that can be increased or decreased in number depending on the total body water content (Regulated by ADH)

Dehydration: High expression of aquaporins in tubules (water reabsorbed to blood)

Overhydration: Low expression of aquaporins in tubules (excess water excreted in urine)

Question 5

Main drivers of solute movement between the intracellular and interstitial fluid compartments?

Answer 5

OSMOTIC PRESSURE and ELECTROCHEMICAL GRADIENTS

Question 6

The pressure that must be applied to a solution to prevent the net flow of water into it?

Answer 6

Osmotic Pressure (π)

Question 7

It is more _________ inside cell, more _______ in the interstitial space

Answer 7

It is more NEGATIVE inside cell, more POSITIVE in the interstitial space

Question 8

Main drivers of solute movement between the interstitial and the plasma compartments?

Answer 8

HYDROSTATIC PRESSURE and ONCOTIC PRESSURE

Question 9

Pressure exerted by a fluid at equilibrium due to the force of gravity, pumping of the heart causing fluid to leak out of capilaries?

Answer 9

Hydrostatic Pressue

Question 10

Type of osmotic pressure, generated by impermeable proteins in solution?

Answer 10

Oncotic Pressure
(Gibbs-Donnan effect)

Question 11

Water distribution in body compartments depends primarily on ________ in the body compartments

Answer 11

Water distribution in body compartments depends primarily on the concentration of electrolytes in the body compartments

Question 12

Normal Osmolality of fluid compartments in a human?

Answer 12

290mOsm

Osmolality of fluid compartments at equilibrium is approximately the same

Question 13

Intercellular Fluid has ________ K+ and ________Na+ relative to Interstitial Fluid

Answer 13

Intercellular Fluid has HIGH K+ and LOW Na+ relative to Interstitial Fluid

Question 14

Ineffective vs. Effective Osmoles?

Answer 14

Ineffective osmole: is a substance that, although osmotically active, can easily distribute across body compartments and so does not cause fluid shifts (ie. Urea)

Effective Osmole: solute contained in compartment (can’t leave) thus attracts water

Question 15

Can a hyperosmotic solution also be an isotonic solution?

Answer 15

Initially cells placed in a hyperosmotic solution would shrink as water moved out into the ECF

Both the ICF and ECF eventually reach the same osmolality, thus no change in cell volume

Question 16

Causes of Isosmotic Dehydration?

Answer 16

Causes:

• Blood loss (hemorrhage)
• Diarrhea & vomiting
• Burns

Question 17

Tonicity of Gastrointestinal fluids (i.e. faeces and vomit)?

Answer 17

Gastrointestinal fluids (i.e. faeces and vomit) are isotonic

Question 18

Tonicity of sweat?

Answer 18

Sweat is hypotonic (Sweating => loss of water in excess of salt)

Question 19

Causes of Hyperosmotic Dehydration?

Answer 19

• Decreased Water intake
• Diabetes insipidus
• Diabetes mellitus
• Alcoholism
• Fever (Excessive Sweat)

Question 20

Causes of Hypoosmotic Dehydration?

Answer 20

Renal loss of NaCl due to adrenal insufficiency (Addison’s disease)

Question 21

Hyperosmotic Dehydration:
Volume of ECF _______
Osmolality of ECF ______
Fluid moves from the ______ to the _______
Volume of both compartments _______
Osmolalities of ECF/ICF equalize at a ________ level

Answer 21

Hyperosmotic Dehydration:
Volume of ECF decreases
Osmolality of ECF increases
Fluid moves from the ICF to the ECF
Volume of both compartments decreases
Osmolalities of ECF/ICF equalize at a higher level

Question 22

Hypoosmotic Dehydration
Osmolality of ECF ________
Fluid moves from the ____ to the _____
Volume of ICF _______
Osmolalities of ECF and ICF equalize at a _______ level

Answer 22

Hypoosmotic Dehydration
Osmolality of ECF decreases
Fluid moves from the ECF to the ICF
Volume of ICF increases
Osmolalities of ECF and ICF equalize at a lower level

Question 23

Solutes and water that enter or leave the body do so via the _______

Answer 23

Solutes and water that enter or leave the body do so via the ECF

Question 24

Equilibration of ICF and ECF osmolality occurs primarily by shifts in ___________

Answer 24

Equilibration of ICF and ECF osmolality occurs primarily by shifts in water (Not shifts in solute)

Question 25

Water loss in excess of solute?

Answer 25

Hyperosmotic Dehydration => contraction of ICF

Question 26

Loss of solute in excess of water?

Answer 26

Hypoosmotic Dehydration => Swelling of ICF