L16: Fluid and Solute balance

Question 1

Focus: What is meant by fluid and solute balance?

Answer 1

maintain homeostasis, what comes in the body must eventually be used or excreted

Question 2

Focus: Describe water balance in the body? What is it and how it is regulated?

Answer 2

Water balance is when the input of water = the output of water
Water input sources are:
1. h20 ingested (2.2L)
2. cellular metabolism byproduct (0.3L)
TOTAL INPUT: 2.5 L

Water output sources are:
1. feces (0.1L)
2. insensible loss + sweating (0.9L)
3. urine (1.5L)
TOTAL OUTPUT: 2.5L

It is regulated by the kidneys

Question 3

Focus: How much of the body is made up of water?

Answer 3

~60% of body weight is water Range: 50% obese to 70% child

70kg adult: total body water = 42 L

Question 4

Focus: How is total body water distributed?

Answer 4

Total body water is everywhere including in blood butttt other than in lumen of GI tract, kidneys, tubules and airways since these are considered outside of the body

Question 5

Focus: How does water move between extracellular and intracellular compartments?

Answer 5

1. osmosis
2. starling forces

Question 6

Equation for fluid and solute balance?

Answer 6

input + produced = used + excreted

-> Input + production = utilization + output

Question 7

The ways we bring h20 into our body and how much h20 is brought in?

Answer 7

1. Ingestion- ~ 2.2L / day
2. Cellular metabolism- 0.3L / day

Question 8

Total water input in a day?

Answer 8

2.5L / DAY

Question 9

Ways h20 is lost in the body?

Answer 9

1.Digestive tract- Feces, 0.1L / day
2. Renal tubles - Urine, 1.5L / day
3. Other losses - 0.9L /day
- insensible loss like respiration we lose h20, ex. cold day.
- sweating

Question 10

What is insensible loss?

Answer 10

h20 loss from surfaces of our body that we don’t detect

Question 11

Total water loss/output in a day?

Answer 11

2.5L / day

Question 12

How much is the total body water in an average 70 Kg adult?

Answer 12

42 L / day

Question 13

Total body water (TBW)

Answer 13

• Everywhere other than in lumen and airways
• 42L =60% of body weight

Question 14

Intracellular fluid (ICF)

Answer 14

• Water in all tissue cells and in RBC’s
• Make up 2/3 of TBW
• 28L

Question 15

Extracellular fluid (ECF)

Answer 15

• Water inside of body but outside of cells
• Plasma included
• 1/3 of TBW
• 14L

2 sections:
- interstitial fluid
- plasma

Question 16

Plasma

Answer 16

• Part of ECF
• in blood vessels plasma but NOT including RBC
• 3L

Question 17

Interstitial fluid (ISF)

Answer 17

• Part of ECF
• outside cells and RBC’s
• outside plasma
• 11L

Question 18

Organize the body water distribution from highest to lowest:

Answer 18

TBW, ICF, ECF, ISF, Plasma

Question 19

What does body water contain and why is it important?

Answer 19

Contains ions, proteins and other molecules
- contribute to osm of ICF/ECF
- influence water movement b/w compartments

Question 20

What comes into cells? what comes out of cells? why is it important for this exchange to happen?

Answer 20

In: Nutrients, electrolytes, water, oxygen, etc

Out: Wastes and unneeded material (including excess water)

Need to have a balance of things coming in and leaving

Question 21

Osmosis, what is it, how water moves

Answer 21

Diffusion of water through a semipermeable membrane
-Always passive
-Unaffected by membrane potentials
-Water moves from area of low osm to high osm

Question 22

Describe the properties of the plasma membrane and water transport occurs

Answer 22

• membrane is hydrophobic
• hydrophobic molecules like lipid soluble molecules can cross, h20 can cross too but only very little
• hydrophilic molecules like ions, glucose, amino acids and water use membrane proteins for transport

H20;
1. can move freely; only a little h20 can move like this
2. most h20 moves through aquaporins which are water channels

Question 23

Molarity

Answer 23

of moles of a substance in a L of solution

Ex. Glucose in powder, weight of glucose x 6x10 to 23 = 180g , calculated by atomic weight of glucose and multiply by Avogadro’s number

examples:
180g of glucose + 1 l of water = 1 M solution of glucose
58.5g + 1 L of water – 1M solution of NaCl

Question 24

Osmolarity

Answer 24

Concentration of particles in 1L solution
- knowing molarity you can find osm

e.g. glucose, stay intact in h20
1 Molar solution of glucose = 1 Osmolar solution of glucose

e.g. NaCl, salts dissociate in h20
1 Molar solution of NaCl = 2 Osmolar solution of NaCl

Question 25

1 osm = ? mOsm

Answer 25

1 osm = 1000 mOsm

Question 26

300mOsm cell placed in pure water that has 0 mOsm, where does the water move?

Answer 26

water moves into cell
- low osm to high osm

Question 27

300mOsm cell placed in 1000mOsm solution, where does the water move?

Answer 27

water moves out of cell
- low to high osm

Question 28

If a cell with an osmolarity of 300 mOsM were placed in a solution of 150 mM NaCl what would happen?

a. It would swell
b. t would shrink
c. No change

Answer 28

c. No change since both osm are the same

Question gave:
- osm of inside cell
- Osm of outside not given, only given molarity
- Using molarity can find osm of outside solution
- Found NaCl osm by x2 since 1M=2osm with NaCl

so… 150mM NaCl = 300mOsm NaCl
- this happens since NaCl dissociate in h20
- 1M NaCl = 2 Osm NaCl

Question 29

What are the 4 starling forces

Answer 29

1. Capillary hydrostatic pressure
2. Tissue oncotic pressure
3. Tissue hydrostatic pressure
4. Capillary oncotic pressure

Question 30

What do the 4 starling forces determine?

Answer 30

• Determine the directionality of net water movement between two different compartments but also determines the rate at which water exchange occurs
  The forces that drive the movement of fluid into and out of capillaries

Question 31

Capillary Hydrostatic Pressure

Answer 31

Hydrostatic pressure exerted by the presence of
fluid inside the capillary
- H2O goes out to tissues
- Filtration

Question 32

Tissue Oncotic Pressure

Answer 32

Force due to presence of proteins in tissues
- H2O goes out to tissues
- Filtration

Question 33

Capillary Oncotic Pressure

Answer 33

Force due to presence of proteins in plasma
- Proteins draw H2O into capillary
- Absorption

Question 34

Tissue Hydrostatic pressure

Answer 34

Hydrostatic pressure exerted by the presence of
fluid outside the capillary
- H2O moves back into capillary
- Absorption

Question 35

Net filtration pressure

Answer 35

Difference between forces for filtration and absorption

Question 36

Pathways for movement of substances into/out of the body