Human Body Water Quiz

Water and Body Fluids

• About 60% of body weight is water (higher in children)
• Water content varies based on body composition
• Lean tissue is mostly water (about 3/4 of weight)
• Fat tissue contains less water (about 1/4 of weight)
• Water proportion is lower in females, obese individuals, and the elderly
• Water functions:
  • Carries nutrients and waste products
  • Maintains large molecule structure
  • Participates in metabolic reactions
  • Acts as a solvent
  • Acts as a lubricant
  • Aids in body temperature regulation
  • Maintains blood volume

Distribution and Movement of Body Fluids

• Every cell contains and is surrounded by fluid
• Intracellular fluid (inside the cell)
• Extracellular fluid (outside the cell, interstitial fluid)
• Continual turnover of fluids
• Rapid adjustments are needed to maintain homeostasis
• Homeostasis is the maintenance of constant internal conditions (e.g., blood chemistry, temperature)

Osmosis

• Water moves from an area of low solute concentration to high concentration across a semipermeable membrane
• When solute is added to one side of a membrane, water moves to equalize the concentrations.

Water Follows Electrolytes

• Some electrolytes reside inside cells (e.g., P, K, Mg, S)
• Some electrolytes reside outside cells (e.g., Na, Cl)
• Water moves to follow the electrolytes across the cell membranes through osmosis.

Fluid and Electrolyte Balance

• Proteins attract water and regulate fluid movement
• Transport proteins facilitate ion passage across cell membranes
• Sodium-potassium pumps regulate fluid and electrolyte balance
• The gastrointestinal tract (GI tract) and kidneys regulate fluid and electrolyte balance.

Blood Volume and Blood Pressure

• Fluids maintain blood volume, influencing blood pressure
• When blood volume or pressure falls:
  • Antidiuretic hormone (ADH) is released, telling kidneys to retain more water and triggering thirst
  • Renin is released by kidney cells, telling kidneys to reabsorb sodium
  • Water retention then occurs as a result of sodium reabsorption
  • Angiotensin II increases blood pressure and signals adrenal glands to release aldosterone.
  • Aldosterone signals the kidney to conserve sodium and excrete potassium, thus again retaining water

Acid-Base Balance

• Body fluid acidity depends on the concentration of H+ ions produced during metabolism.
• pH needs to be neutralized through buffers in the blood; respiration in lungs; excretion by kidneys.
• The bicarbonate-carbonic acid buffer system regulates pH. Carbon dioxide (CO2) and water (H2O) form carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3−). This system helps to maintain a stable pH within the body's fluids.

Water Intake

• Controlled by the hypothalamus (responsible for thirst)
• Decreased water or increased concentration of blood leads to increased thirst.
• Increased water or distension of stomach leads to decreased thirst.

Water Recommendations

• Adults: 1.0 to 1.5 mL of water per kcal expended
• Infants and athletes: 1.5 mL of water per kcal expended
• Men: 3.7 L/day.
• Women: 2.7 L/day.

Sodium

• Table salt (NaCl) is a source of sodium

• Preserves food and enhances taste

• Roles: fluid balance, acid-base balance, nerve transmission, and muscle contraction

• Readily absorbed in the blood and travels to the kidneys.

• Adequate Intake (AI) for sodium: -19-50 years: 1500 mg/day -51-70 years: 1300 mg/day -70+ years: 1200 mg/day

• CDRR for sodium: 2300 mg/day (to reduce risk of chronic diseases)

Chloride

• Chloride (Cl−) is an essential nutrient
• Involved in fluid and electrolyte balance
• Associated with sodium outside and potassium inside cells
• Moves passively through membrane channels
• Part of hydrochloric acid (HCl), crucial for digestion
• Abundant in foods, often consumed as part of salt.
• Deficiency and toxicity are uncommon

Potassium

• A cation found inside cells
• Roles: fluid and electrolyte balance, nerve transmission, muscle contraction
• Sodium and potassium exchange places rapidly to maintain balance.

Phosphorus

• Important role in various body functions.
• Sources include protein-rich foods (such as milk, meat, and legumes).

Fluid and Electrolyte Imbalance

• Causes: prolonged vomiting, diarrhea, heavy sweating, burns, traumatic wounds, certain medications
• Solutes in lost fluids depend on the reason for fluid loss (e.g., sodium in sweat)
• Replacement of lost fluids and electrolytes is necessary.

Dehydration

• Water loss exceeds intake, resulting in a negative water balance
• Causes include diarrhea, vomiting, fever, excessive sweating, unmanaged diabetes, and diuretic use.

Heat Illnesses

• Heat cramps, exhaustion, and stroke
• Causes: strenuous activity in hot environments, inadequate water intake

Water Intoxication

• Causes hyponatremia (low sodium in blood)