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WATER IN THE BODY

WATER IN THE BODY. WATER IN THE BODY. The body contains two fluid “compartments.” Intracellular compartment, refers to fluid inside cells Extracellular compartment includes (1) blood plasma (_20% of total extracellular fluid)

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WATER IN THE BODY

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  1. WATER IN THE BODY

  2. WATER IN THE BODY The body contains two fluid “compartments.” • Intracellular compartment, refers to fluid inside cells • Extracellular compartment includes • (1) blood plasma (_20% of total extracellular fluid) • (2) interstitial fluids, which primarily comprise fluid flowing in microscopic spaces between cells.

  3. Sources of interstitial fluid include: • 1. Lymph • 2. Saliva • 3. Fluids in the eyes • 4. Fluids secreted by glands and the digestive tract • 5. Fluids that bathe the nerves of the spinal cord • 6. Fluids excreted from the skin and kidneys • Much of the fluid lost through sweating comes from extracellular fluid, predominantly blood plasma

  4. Functions of Body Water • 1. Provides the body’s transport and reactive medium. • 2. Diffusion of gases occurs across moist body surfaces. • 3. Waste products leave the body through the water in urine and feces. • 4. Absorbs considerable heat with only minimal changes in temperature from its heat stabilizing qualities. • 5. Watery fluids lubricate joints, keeping bon surfaces from grinding against each other. • 6. Being non compressible, water provides structure and form through the turgor it imparts to the body’s tissues.

  5. Water Balance: Intake Versus Output The water content of the body remains relatively stable over time. Appropriate fluid intake rapidly restores an imbalance

  6. Water Intake • In a normal environment, a sedentary adult requires about 2.5 L of water daily. • For an active person in a warm environment, the water requirement often increases to between 5 and 10 L daily.

  7. The sources of water intake: • 1. Liquids • 2. Foods • 3. Metabolic processes

  8. Metabolizing food molecules for energy forms carbon dioxide and water. • For a sedentary person, metabolic water provides about 25% of the daily water requirement. • Additionally, each gram of glycogen joins with 2.7 g of water as the glucose units link together thus making glycogen a heavy energy fuel. • Glycogen subsequently releases this water during its catabolism for energy.

  9. Water Output • The body loses water in four ways: • 1. In urine • 2. Through the skin • 3. As water vapor in expired air • 4. In feces

  10. WATER REQUIREMENT DURING EXERCISE • The factors determine water loss through sweating: 1. Severity of physical activity : The evaporative loss of 1 L of sweat releases about 600 kCal of heat energy from the body to the environment. 2. Environmental temperature

  11. 3. Humidity: • Relative humidity, which refers to the water content of the ambient air, impacts the efficiency of the sweating mechanism in temperature regulation. • At 100% relative humidity, the ambient air is completely saturated with water vapor. • This blocks evaporation of fluid from the skin surface to the air, thus minimizing this important avenue for body cooling. • When this happens, sweat beads on the skin and eventually rolls off without generating a cooling effect.

  12. The major physiologic defense against overheating comes from evaporation of sweat from the skin’s surface. • sweat loss equal to 2% to 3% of body mass decreases plasma volume. This amount of fluid loss strains circulatory functions and ultimately impairs exercise capacity and diminishes thermoregulatory control.

  13. Practical Recommendations for Fluid Replacement in Exercise: Pre-exercise hyperhydration • (1) delays dehydration. • (2) increases sweating during exercise. • (3) blunts the increase in body temperature compared with exercising without prior fluids. • As a practical step, a person should consume 400 to 600 mL (13–20 oz) of cold water 10 to 20 minutes before exercising.

  14. How to Distinguish Among Heat Cramps, Heat Exhaustion, and Heat Stroke

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