Body Fluids

Question 1

Homeostasis

Answer 1

The relative constancy of the Milieu Interieur
All functional activities are directed at maintaining homeostasis

Question 2

Milieu Interieur

Answer 2

Internal environment remains relatively constant under conditions of health

Question 3

Body water

Answer 3

-most abundant constituent of the body
- large variance of water content person to person (45-75 %)
-where solutes are dissolved and metabolic reactions take place

Question 4

% of Water in Various Tissues

Answer 4

Skin - 70%
Muscle 0 75 %
Heart, Liver, Brain, Kidney - 70-80 %
Bone - 25 %
Fat - 10 %

Question 5

Body Water proportion of Total body mass

Answer 5

Physiological reference individual: 60% water
More adipose tissue: Less than 60 % (45%)
Less adipose tissue: Over 60 % (75%)

Question 6

If body water content is computed as a fraction of LEAN BODY MASS (excluding FAT) the differences between individuals become…

Answer 6

insignificant

Question 7

Variations in body water with age and sex

Answer 7

-Decreases with age
-Male is greater than female

Infants ~ 75% (same in male and female)
Woman ~ 50% (more adipose tissue)
Man ~ 60%
Elderly ~ Less than 50% / 60%

Question 8

Calculations of Body Water

Answer 8

Weight (kg) * % Water (%) = Water content (L)
For standard male: 42 L

Question 9

Calculations for medication dosing

Answer 9

Water-soluble medications
Weight (kg) * % Water (%) = Water content (L)
mg medication (mg) / Water content (mL) = dose

Question 10

Body water is in “Dynamic Steady State”

Answer 10

Between the individual and external environment and internally between compartments

Question 11

Water Balance Intake

Answer 11

Intake (2.7 L)
-Oral Fluid 1.2 L
-Oral intake in food 1.1 L
-Oxidative water from metabolism 0.4 L

Question 12

Water Balance Output

Answer 12

Output (2.7L)

Insensible (Obligatory)
-Lungs 0.4 L
-Skin (passive evaporation) 0.5 L

Sensible (Obligatory)
-Kidneys 0.5 L
-Stool 0.1 L

Facultative: losses vary with intake
-maintain balance with urine
-1.2 L

Sweat

Question 13

Insensible Perspiration

Answer 13

-pure water
-passive evaporation
-from entire skin surface
-continuous and obligatory

Question 14

Sweating

Answer 14

NEITHER OBLIGATORY NOR FACULTATIVE
(but still an output)
-Electrolyte solution
-Active secretion
-Sweat glands
-Activated by heavy work / high temp

Question 15

Water turnover

Answer 15

Adult: 3-4% a day
Infant: ~10% a day

Infant- greater surface area : volume ratio = more passive evaporation

Question 16

Negative Water Balance

Answer 16

Water loss > Water intake
1. Reduced Intake
2. Excessive Loss from Gut
3. Excessive Sweating
4. Excessive Loss in Expired Air
5. Excessive Loss in Urine

Question 17

Water Intoxication

Answer 17

Water loss < Water intake
1. Excessive intake
2. Renal system failure

Question 18

Body Water Compartment

Answer 18

ICF (Intracellular Fluid):
-2/3
-40% of body mass
~28 L

ECF (Extracellular Fluid)
-1/3
-20% of body mass
~14 L

Question 19

ECF compartment divisions

Answer 19

2 Major subcompartments
- Plasma
- ISF (Interstitial fluid)

2 Minor subcompartments
-Lymph
-Transcellular Fluid

Water moves into capillaries becomes plasma and moves out becomes ISF

Question 20

Plasma

Answer 20

the fluid medium, in which blood cells are suspended
- 1/3 of the ECF
-5% of body mass
~3.5 L

Question 21

Centrifuged Blood

Answer 21

-Plasma ~55%
-Buffy Layer (WBCs and platelets) ~1%
-RBCs ~45%

Question 22

Hematocrit

Answer 22

(height of erythrocyte column / height of whole blood column)

Percent of blood occupied by RBCs
Normal value ~45%

Question 23

Interstitial Fluid (ISF)

Answer 23

The fluid which percolates between individual cells
- 2/3 of the ECF
-15% of the body mass
~10.5 L

Question 24

Lymphatic System

Answer 24

~1-2% of ECF

Question 25

Compartment % of Body Weight

Answer 25

Total H20 - 60% ICF - 40% ECF -20% ISF - 15% Plasma -5%

Question 26

Transcellular fluid

Answer 26

Aggregate of small fluid volumes secreted by specific epithelial cells that line some body cavities Have specialized functions in part of body ~ < 1-2% of ECF Does not contribute to overall water exchange

Question 27

Methods to Determine Compartment Volumes

Answer 27

Direct: volume measurement Indirect: Indicator dilution method

Question 28

Indicator dilution method

Answer 28

V = Q / c 1. Total quantity of test substance introduced (Q) 2. Concentration of substance / unit volume of plasma (c)

Question 29

(IDM): Total Body Water measurement

Answer 29

-Antipyrine, D2O, or T2OQ -Can pass through cell membrane and capillary wall

Question 30

(IDM): ECF measurement

Answer 30

-inulin, sucrose, mannitol -Can pass through capillary wall but not cell membrane -Stays within the ECF (does not pass into cells)

Question 31

(IDM): Plasma measurement

Answer 31

-Evans’ Blue (T1824) or I131-Albumin -Can not pass through capillary wall -Remains within the capillaries

Question 32

(IDM): ICF and ISF calculations

Answer 32

Total Body Water - ECF = ICF ECF - Plasma = ISF

Question 33

Ionic composition

Answer 33

ICF -High in K+ (and Mg++) -Low in Na+and Cl- ECF -High in Na+and Cl- (0.9 % NaCl) -Low in in K+ IN ECF -plasma has proteins anions -ISF has no proteins (GRADIENT)

Question 34

Artificial Physiological Solutions

Answer 34

substitute for ECF fluids (plasma/ISF) Physiological Saline = 0.9% NaCl

Question 35

Barriers” to Transport

Answer 35

Cell membrane : between ICF and ECF Capillary wall: between ECF/ISF and plasma

Question 36

Body Fluid Ionic Composition

Answer 36

ECF approximated by 0.9 % NaCl 300 mOsm = 6.7 atm ~ 5100 mmHg