Fluid balance

Two-thirds of body weight is water.
75 kg of body weight containing approximately 38.4 liters of water in the body, where:
- 23-27 L in the cell
- 7.7 L in the space between cells and
- Less than 3.84 L or approximately 8% of the total water, is in the bloodstream.
The amount of fluid is relatively small in blood flow is essential for body functions and must continue to be kept constant.
Water beyond the blood flow serves as a backup who can fill as well as absorb excess water in the blood as needed.

Water enters the body primarily through the absorption from the digestive tract.
Water leaves the body primarily as urine released from the kidney.
Kidneys can release up to several liters of urine in a day or can be held to dispose of less than 0.5 L of urine a day.

Approximately 1 L of water was also removed every day through evaporation from the skin and lungs.
Excessive perspiration (such as heavy exercise or hot weather), can increase the amount of water lost through evaporation.

In normal circumstances, a little water discharged through the digestive tract.
On prolonged vomiting or diarrhea is severe, as much as 3.84 liters of water can be lost through the digestive tract.

If fluid intake with fluid loss, body fluids will remain in balance.
To maintain fluid balance, healthy people with normal kidney function and no excessive sweating, should drink at least 1 L fluid / day.
To prevent dehydration and the formation of kidney stones, it is recommended to drink fluids as much as 1.5-2 L / day.

When the brain and kidneys function properly, the body can cope with extreme changes in fluid intake.
A person usually can drink enough fluid to replace the excessive water loss and maintain blood volume and concentration of salts dissolved minerals (electrolytes) in the blood.
If someone can not drink enough water to replace the excessive loss of water (as happens in the ongoing vomiting or diarrhea great), it can become dehydrated.

The amount of water in the body is closely related to the amount of body electrolytes.
Blood sodium concentration is a good indicator of the amount of fluid in the body.

Body trying to maintain the total number of body fluids so that the blood sodium levels remained stable.
If sodium levels are too high, the body will retain water to dissolve the excess sodium. Will arise thirst and less urine out.
If sodium levels are too low, the kidney secretes more water to restore sodium levels returned to normal.