Water, electrolytes, and an acid-base balance are very important in the proper function of the body, particularly the urinary system.
Between 50% and 70% of a person’s weight is water: 60% for the adult male and 50% in the adult female. An infant is composed of 75% water.
Because adipose tissue contains less water than muscle tissue, the obese have less water than a thin person.
Water and electrolytes are distributed into two major compartments: intracellular and extracellular.
- Intracellular compartments hold the most water in the body – 63%. Intracellular fluid contains high concentrations of potassium, phosphate, and magnesium ions.
- Extracellular water (37%) is found between cells (interstitial fluid), within blood vessels (plasma), and within lymphatic vessels (lymph).
- Transcellularfluid is also extracellular fluid that includes:
- cerebrospinal fluid
- aqueous and vitreous humors in the eyes
- synovial fluids of joints
- serous fluids in body cavities
- glandular secretions
- Interstitial fluids and plasma comprise the largest amounts of extracellular fluids.
- Transcellularfluid is also extracellular fluid that includes:
Water metabolism consists of a daily intake of approximately 2,500 ml of water with 60% coming from drinking, 30% from water in foods, and 10% from the breakdown of foods.
The thirst center is in the hypothalamus of the brain. Water elimination occurs through several routes:
- kidneys (60%),
- skin and lungs (28%)
- feces (6%)
- sweating (6%).
