Body Fluids

Question 1

What is the function of water?

Answer 1

• medium for all metabolic processes
• diffusion of nutrients and waste products
• solvent
• homeostasis

Question 2

What is the consequence of having too little water in the body?

Answer 2

Diarrhoea and very low blood pressure - 90/40mmHg

Question 3

What is the consequence of having too much water in the body?

Answer 3

Kidney failure and very high blood pressure- 200/100mmHg

Question 4

If there was an intake of 2300ml of water, what would it be used for?

Answer 4

Ingested= 2100ml
Metabolism= 200ml

Question 5

If there was an output of 2300ml of water, what would it be used for?

Answer 5

Urine= 1400ml
Loss from skin= 350ml
Loss from lungs= 350ml
Faeces= 100ml
Sweat= 100ml

Question 6

Where can fluid be found inside the body?

Answer 6

Inside cells, interstitial fluid or blood plasma

Question 7

The body is 60% water, how much of that forms the intracellular and extracellular fluid?

Answer 7

Intracellular= 40%
Extracellular= 20%

Question 8

Why is the composition of body fluids in each compartment different?

Answer 8

As each compartment has different ions

Question 9

Which ions does the intracellular compartment contain?

Answer 9

Potassium and phosphate ions

Question 10

Which ions does the interstitium contain?

Answer 10

Sodium and chloride ions

Question 11

Which ions does the blood plasma contain?

Answer 11

Sodium and chloride ions

Question 12

What is the difference between the permeability of the capillary membrane and the plasma membrane?

Answer 12

Capillary membrane is more permeable than the plasma membrane. Plasma membrane only allows specific molecules to pass through

Question 13

Which molecules does the plasma membrane allow through?

Answer 13

Sodium, chloride, potassium and phosphate ions

Question 14

Which ions are found inside and which are found outside of the cell?

Answer 14

Inside= potassium and phosphate ions
Outside= sodium and chloride ions

Question 15

What regulates the concentration of sodium and potassium ions and how?

Answer 15

Na+/K+ pump, 3 sodium ions pumped out, 2 potassium ions pumped in

Question 16

What do fluid movements depend on?

Answer 16

Ionic and osmotic pressure and the nature of the barrier

Question 17

What drives the movement of water in and out of the cell membrane?

Answer 17

Osmotic pressure

Question 18

What is the structure of the capillary wall barrier?

Answer 18

It has endothelial cells and are separated by semi-permeable pores

Question 19

What drives the movement of water in and out of the capillary wall barrier?

Answer 19

Hydrostatic pressure

Question 20

What is the definition of osmosis?

Answer 20

The net diffusion of water across a selectively permeable membrane from a region of high water potential to a region of low water potential

Question 21

What is the unit of measurement of osmosis?

Answer 21

An osmole

Question 22

What does an osmole describe?

Answer 22

The concentration of solute particles in a solution

Question 23

What is 1 osmole equal to?

Answer 23

1 osmole= 1 mole= 6x10^23 osmotically active particles

Question 24

What is osmolality?

Answer 24

Osmole/kg of solvent

Question 25

What is osmolarity?

Answer 25

Osmole/L of solution

Question 26

How can osmolarity be changed?

Answer 26

By changing temperature

Question 27

What is the osmolarity of the different fluid compartments and what does this mean?

Answer 27

The osmolarity is very similar across the 3 fluid compartments This means water can move freely across both types of wall

Question 28

How is osmotic pressure balanced and when does this change?

Answer 28

Osmotic pressure is balanced between intracellular and extracellular fluid This changes when we drink

Question 29

What is the definition of tonicity?

Answer 29

The effect of a solution on the osmotic movement of water

Question 30

What can a solution's osmolality affect?

Answer 30

Cell size

Question 31

What happens when there are rapid changes in serum sodium concentration?

Answer 31

Causes swelling of brain fits resulting in confusion and fits

Question 32

What is a hypotonic soloution and what does it result in?

Answer 32

A hypotonic solution is when there is a higher water potential outside than inside, so water moves into the cell Causes cells to become swollen and eventually start lysing

Question 33

What is a hypertonic soloution and what does it result in?

Answer 33

A hypertonic solution is when there is a higher water potential inside than outside so water moves out of the cell Causes cells to become crenated

Question 34

How is the volume of total body water measured?

Answer 34

Using radioactive water that is distributed in all the compartments

Question 35

How is the volume of extracellular water measured?

Answer 35

Using radioactive insulin that doesn't enter the cells

Question 36

How is the volume of plasma measured?

Answer 36

Using radioactive albumin that stays in the plasma only

Question 37

How is intracellular volume measured?

Answer 37

Total body water - extracellular volume

Question 38

How is interstitial volume measured?

Answer 38

Extracellular volume - plasma volume

Question 39

What does fluid accumulation in the lungs cause?

Answer 39

Shortness of breath

Question 40

What does fluid accumulation in the lower limb cause?

Answer 40

Discomfort

Question 41

What are the causes of oedema?

Answer 41

Increased capillary fluid pressure Decrease in capillary osmotic pressure Leaky membrane which affects the coefficient Blocked lymphatics