Body Fluids

Question 1

What is Homeostasis

Answer 1

Keeping constancy of internal environment within cells (human body), even if external environment changes

Question 2

% of water in various tissues

Answer 2

skin = 70%
muscle = 75%
heart, liver, brain, kindey = 70-80%

bone = 25%
Fat (adipose tissue) = 10%

Question 3

Lean body mass water content

what is it

Answer 3

Excludes water content of fat

Question 4

What accounts for the large variation in water content in different individuals

Answer 4

Various fat levels in body create water % differences

Question 5

Body water along the years

Answer 5

age male female
infant 65% 65%
10-18 59% 57%
18-40 61% 51%
40-60 55% 47%
>65 50% 45%

Question 6

What makes body water change in male vs females and in both?

Answer 6

males: Have more testosterone which increases muscle mass (more water)
females: oestrogen during puberty = less water
both: Aging = more adipose tissue and muscles diminish, so water is lost

Question 7

How to find body water

Answer 7

(Mass(kg) x % water)/100 =body water
in kg which can be put in L

Question 8

How to calculate how much water-soluble medication you can administer

Answer 8

dosing = 10mg/7kg

find body water:
(mass x %H2O)/100
ex: (70kg x 60%)/100 = 42L

conversion body water into mL
ex: 42L = 42 000 mL

Find mass of medication:
mass of person x dosing
ex: 70kg x (10mg/7kg) = 100mg

Final concentration:
mass medication/ body water
100mg/42 000 mL
= 0.0024mg/mL

Question 9

Important units prefixes

Answer 9

milli (m) = 10^-3
micro = 10^-6
nano (n) = 10^-9
pico (p) = 10^-12

Question 10

Intakes to maintain water balance (with values)

Answer 10

oral fluid = 1.2L
oral intake as food =1.1L
Oxidative H2O from metabolism = 0.4L

total 2.7L

Question 11

Outputs to maintain water balance (obligatory + facultative) and values

Answer 11

Obligatory: (always happen)
insensible: total 1.0L
lungs = 0.4L
skin = 0.5L (passive evaporation)
sensible:
Kidneys: urine = 0.5L
Stool: feces = 0.1L

Facultative
Urine = 1.2L
if more H2O is taken in, more urine is produced

Sensible loss: sweat (amount varies)

Total around 2.7L

Question 12

Characteristics of insensible perspiration

Answer 12

Insensible perspiration
1. pure water
2. passive evaporation
3. entire skin (no need for sweat glands)
4. continuous and obligatory

Question 13

Characteristics of sweating

Answer 13

1. electrolyte solution
2. active secretion
3. from sweat glands
4. activated by heavy work or high temp (non continuous)

Question 14

Water turnover

Answer 14

over 24 hours

Adults: 3-4% of body weight

Infants: 10%
should only drink baby formula and breast milk because kidneys lose ions
Smaller body volume = water leaves more quickly

Question 15

Types of negative water balance

Answer 15

1. Reduced intake (normal is 1.5L everyday)
2. Excessive loss from Gut (people die from dehydration because of diarrhea)
3. Excessive sweating
4. Excessive loss in expired air (air is dry at high altitudes = need to breath more, so more water lost from lungs)
   5.Excessive loss in urine

Question 16

Types of water intoxications

Answer 16

1. Excessive intake (marathon runners that drink too much)
2. Renal system failure

Question 17

Physiological reference individual

Answer 17

21 years old white male
70kg => 60% body water

Question 18

Body water compartments

Answer 18

total body water = 60%
Intracellular fluid = 2/3 of 60%
Extracellular fluid = 1/3 of 60%

volumes remain constant
dynamic equilibrium

Question 19

Subdivisions of ECF

Answer 19

Major:
Plasma = 1/4 of ECF
Interstitial fluid = 3/4 of ECF

Minor:
Lymph around 1-2% of ECF
Transcellular fluid

Question 20

Hematocrit (Ht)

Answer 20

percentage of blood occupied by RBC (erythrocytes)

Ht = (height of RBC column)/ (height of whole blood column)
ex: Ht = 45/100 = 45%

normally 45%

Question 21

Lymphatic system

Answer 21

network of blind-ended terminal tubules

form larger lymphatic vessels

converge to form large lymphatic duct

drain into large veins in chest

unidirectionnal

Question 22

Transcellular fluid

Answer 22

Minimal amounts of fluid (<1- 2% of ECF) made by epithelial cell in some body cavities.
Have specialized functions (saliva helps digest food)

Does not affect body fluid balance

Question 23

Direct method to determine compartment volume

Answer 23

Weigh compartment with substance inside then dry it out and reweigh

or for simple shapes use volume formulas: V=pi(r)^2 x h

Question 24

Indirect method of determining compartment volume (Indicator dilution method)

Answer 24

Introduce known total quantity (Q) of indicator (died with radioactive material) into vein

allow equilibrium

Remove known volume of blood and centrifuge to get plasma

Measure concentration (c) in unit volume of plasma

Calculate V=Q/c

Question 25

Indicators used

Answer 25

non-toxic
no change in H2O distribution
easy to measure concentration

Total body water: normal 42L
Antipyrine, D2O, T2O
(can cross all membranes)

Total ECF: normal 14L
inulin, sucrose, mannitol
(Cannot cross cell membrane into intercellular fluid)

Total Plasma: normal 3.5L
evans’ Blue
(cannot cross capillary wall)

ICF = Total BW - ECF

ISF = ECF - plasma

cannot measure lymph nor transcellular fluid

Question 26

Ionic composition of body fluids

Answer 26

ICF: high in K+ and Mg++
low in Na+ and Cl-

ECF: high in Na+ and Cl- but low in K+ (0.9% NaCl)

Substitute for plasma: Physiological Saline
= 0.9% NaCl
(9g NaCl + H2O to make up 1L)