Normal fluid physiology

Question 1

What percentage of total lean body weight is made up of water?

Answer 1

About 60%

This percentage reflects the total body water distribution across different compartments.

Question 2

What are the two major body fluid compartments?

Answer 2

• Intracellular
• Extracellular

Question 3

What percentage of total body weight is intracellular fluid?

Answer 3

40%

Question 4

What percentage of total body water is accounted for by extracellular fluid?

Answer 4

33%

Question 5

What are the two sub-compartments of extracellular fluid?

Answer 5

• Interstitial (outside blood vessels)
• Intravascular (inside blood vessels)

Question 6

What is the percentage of interstitial fluid within the extracellular fluid?

Answer 6

75%

Question 7

What is the percentage of intravascular fluid within the extracellular fluid?

Answer 7

25%

Question 8

What regulates the movement of water between compartments?

Answer 8

Permeability of barriers and solute concentration differences

Question 9

What type of membrane separates intracellular and extracellular compartments?

Answer 9

Semi-permeable cell membrane

Question 10

What can freely cross the cell membrane?

Answer 10

Water

Question 11

What are the main colloid particles within plasma?

Answer 11

• Albumin
• Globulins
• Fibrinogen

Question 12

What does osmotic pressure (‘tonicity’) mean?

Answer 12

The ability of particles in a compartment to cause water movement

Question 13

What is total fluid osmolality?

Answer 13

A measure of all particles dissolved within a fluid compartment

Question 14

How is osmolality calculated?

Answer 14

2(Na+ + K+) + glucose + BUN

Question 15

What is the normal serum osmolality for dogs?

Answer 15

Around 300 mOsm/kg

Question 16

What is colloid osmotic pressure (COP)?

Answer 16

The contribution of colloid particles to plasma osmotic pressure

Question 17

What is the normal COP in dogs?

Answer 17

21-25 mmHg

Question 18

What is the classical theory of fluid flux across capillaries based on?

Answer 18

Oncotic and hydrostatic pressure gradients

Question 19

What does Starling’s equation describe?

Answer 19

Net fluid filtration across capillaries

Question 20

What is the revised Starling principle?

Answer 20

Fluid flux is determined by oncotic pressure difference between plasma and subglycocalyx space

Question 21

What is the glycocalyx?

Answer 21

A gel-like matrix on the luminal surface of endothelial cells

Question 22

What role does the glycocalyx play in vascular physiology?

Answer 22

• Vascular permeability
• Mechanotransduction
• Blood cell interactions
• Control of microenvironment

Question 23

What has shedding of the glycocalyx been associated with?

Answer 23

Poorer outcomes in various disease processes

Question 24

What is the primary electrolyte difference between extracellular and intracellular fluid?

Answer 24

High extracellular sodium and high intracellular potassium

Question 25

What pump maintains the sodium and potassium concentration differences across cell membranes?

Answer 25

Na/K ATPase pump

Question 26

What ion concentration is measured in standard biochemical tests?

Answer 26

Solutes within the extracellular fluid (ECF) only

Question 27

What is the concentration of sodium in intravascular fluid?

Answer 27

145 mEq/L

Question 28

What is the concentration of potassium in intracellular fluid?

Answer 28

120 mEq/L

Question 29

Fill in the blank: The only difference between intravascular and interstitial fluid is the concentration of _______.

Answer 29

Proteins

Question 30

True or False: The concentration of chloride in intracellular fluid is higher than in intravascular fluid.

Answer 30

False