Body Fluid and Osmolarity

  1. Describe the body composition of the average male?
    • 60% water
    • 40% solids (carbs, fats, proteins, and minerals)
  2. Compare the body fluid composition in males, females and neonates
    • Males are made up of 60% water
    • Females (52%) have less water content, more subcutaneous fat
    • Neonates are made up of 75% water
  3. Describe the percentage weight of the following
    • Total body water: 60%
    • Intracellular fluid: 40%
    • Extracellular fluid: 20%
    • Plasma: 5%
    • Intercellular: 15%
  4. Calculate the Total Body Water, intracellular fluid, and interstitial fluid of 70kg adult male
    • 70 x 60/100 = 42.0 L
    • 70 x 40/100 = 28.0 L
    • 70 x 15/100 = 10.5 L
  5. What is the internal environment?
    • Intercellular fluid that bathes the cells
    • It is an ultrafiltrate of blood
  6. Name the main cations inside and outside the cell
    • K is inside the cell
    • Na is outside
  7. Name the major anions inside and outside the cell
    • PO4 and plasma proteins are inside the cell
    • Cl- and HCO3- is outside
  8. Define Homeostasis
    The process of maintaining a constant extracellular fluid
  9. What is osmotic pressure?
    The tendency of water to move into a solution based on its concentration of solutes and water
  10. Describe osmolarity
    • number of solutes/volume of water
    • its regulated by two mechanisms: 1. ADH 2. Thirst
  11. What is the hypothalamus
    part of the brain that maintains homeostasis, and it controls osmolarity
  12. How much water is secreted in the following:
    • Skin: 400 ml
    • Lungs: 500 ml
    • Urine: 1600 ml
    • Feces: 200 ml
  13. Name 3 causes of overhydration
    • Athletes who drink only water
    • Ecstasy
    • Syndrome of inappropriate ADH secretion
  14. Discuss the effects of overhydration
    • Excess water distributes in the ECF
    • Osmolarity of ECF decreases
    • Water moves into all cells
    • Osmolarity of ICF decreases
    • Disturbs cellular function
  15. Discuss the symptoms of water retention
    • Neuronal
    • Nausea, lethargy, confusion, convulsions and coma
    • This is mainly because disturbance of brain cell osmolarity
    • Non-neural
    • Weakness
  16. What is the effect of Diabetes Mellitus on ECF sodium?
    Blood glucose is an effective osmole. It draws water out of cells into the ECF. This dilutes sodium concentration in the ECF (pseudohyponatremia)
  17. Name 3 causes of dehydration
    • Insufficient water intake
    • Excessive water loss through sweating, emesis, and cholera
    • Diabetes insipidus
  18. What is diabetes insipidus and what is its treatment?
    • Deficiency in ADH
    • Symptoms include hypernatremia, polyuria, and polydipsia
    • Treated by vasopressin
  19. Discuss the mechanism of maintaining blood osmolarity
    1st with concentrated plasma
    2nd with diluted plasma
    • Concentrated plasma is detected by osmoreceptors in the brain
    • ADH is secreted from the posterior pituitary
    • This increases water reabsorption in distal tubules and collecting ducts
    • Dilute plasma is detected by osmoreceptors in the brain
    • ADH secretion is turned off
    • This inhibits water reabsorption by distal tubules collecting ducts
  20. Discuss the effects of dehydration
    • Water content in ECF decreases
    • ECF osmolarity increases
    • Water is drawn out of cells
    • Osmolarity inside all cells increases
    • Disturbs cellular function
  21. Discuss symptoms of dehydration
    • Neuronal: confusion, irritability, convulsions and coma
    • Non Neuronal: low blood pressure, lethargy, sunken eyes, circulatory shock, death
  22. What is an osmole?
    • its a measure of the amount of moles of electrolytes
    • 1 Osmole = 1 mole of osmotically active molecules
  23. What is the composition of isotonic saline?
    • 0.9% NaCl (0.9 g/100 ml water)
    • *0.9 g/100 ml = 9.0 g/L x 1 mol/58 g x 1000 = 310 mosmol/L
  24. To whom might an intravenous solution of 3% NaCl be administered?
    To people who have low plasma osmolarity as a result of water entering the cell
  25. To whom might an intravenous solution of 0.45% NaCl be administered?
    • To people who have high plasma osmolarity as a result of water leaving the cell
    • To people with renal disease who need rehydration but no additional sodium
  26. How is neurological function altered in SIADH?
    Nausea, lethargy, confusion, convulsions, and coma
  27. Briefly describe how the SIADH affects the osmolarity of the ECF and ICF
    • Excess water is reabsorbed in the distal tubules and collecting ducts
    • Excess water of distributed in ECF
    • ECF osmolarity decreases
    • Water enters all cells
    • ICF osmolarity decreases
    • Disturbs cellular function
  28. What is SIADH secretion?
    • Failure to turn off ADH secretion in response to drop in plasma osmolarity
    • Result in water loading, dilutional hyponatetremia, and concentrated urine without signs of edema
    • Treated by restricting water intake and diuretics
Card Set
Body Fluid and Osmolarity