Body Fluids

Body Fluids 

Body compositions

• In the average young adult male:

1. Water      60% ( TBW)
2. Protein    18%.
3. Fat           15%.
4. Minerals    7 %
5. carbohydrates < 1 %

• The cells of the body live in a fluid environment.Th e interstitial fluid which represents the internal environment.
• The function of all organ system is to ensure that the physical characteristics of the tissue fluids remain constant within narrow limits.
• So pH, temp, the concentration of chemical components of the internal environment are precisely regulated

Body fluids :

• Represent 60% of body weight = 40 liters
• Factors affect body fluids

1. age: amount varies with age newborn  73-82%, adult 60 %, old age 45-50%.
2. loss of body water is a common cause of death in children
3.  body fats: lean subject more water than obese
4. sex: women more fat and less water 

Body fluid compartment :

• Body fluids are distributed into two compartments:

1. intracellular fluid compartment.
2. Extracellular fluid compartment.

• Intracellular fluid :

•  2/3 of body water

•  40% of body weight = 25 liters

• Extracellular fluid :

•  1/3 of body water

•   20% of body weight=15 liters

•   Further divided into 3 compartment:

1. interstitial fluids:

• surround the cells

• comprises ¾ of  ECF = 15% of Body Weight =12 liters

• include lymph which cannot be measured separately

1. Plasma:

• intravascular fluids

• comprises ¼ of ECF = 5% of BW =   3liters

1. Transcellular fluid:

• Fluid which are found out side normal compartment

• Secreted by epithelium lining eg cerebrospinal fluid, GIT and urinary fluids, fluids in potential spaces eg joint cavities, and in pleural and peritoneal spaces

• Total amount is small (.5 L) but large volumes can be formed in disease state eg ascites.

 VOLUME OF BODY FLUIDS IN 70 kg MAN TOTAL VOLUME 40 L.

• ECF:  ICF 

• Is  larger in infants and children than in adults but the absolute  ECF volume is smaller in children than in  adults. 

• That’s why children tend to dehydrate more  rapidly  and  more  sever.

• TBW : BW

• The  ratio varies with  the  amount  of fat  present.   this variable   leads   to the   variation  due to age   and  gender

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Many functions of body fluid :

1. Lubrication
2. Medium for cellular activities
3. Transport of nutrients
4. Temperature regulation
5. Elimination/excretion of waste

Measurement of body fluids :

• Volumes in various compartments measured using dilution method

V (Volume) = Q (Quantity) - E (excreted) /C (Concentration)

Ficks Principle :

• Amount = vol. X conc.
• Vol. = A/C  (in plasma)

Measurement of body fluid compartment:

• Using indicator (dye)dilution method.
• A known quantity of a substance(e.g. a dye) Is injected and allowed to distribute in the compartment of interest.
• measure the final concentration of the dye from the compartment then the volume of the compartment(=volume of distribution of the dye).Calculated using the formula: volume of distribution =Q-e /c

Characteristic of substance :

1. Not Toxic
2. Distribute itself in a certain compartment to be measured
3. Should distribute itself uniformly in all part of the fluid to be measured
4. No effect of its own on the distribution of water or other substances in the body
5. Must be unchanged  by the body during mixing or amount changed must be known
6. Easy to measure