Water serves vital functions in the body, including transporting nutrients and waste, regulating temperature, and facilitating metabolism. Body composition varies by factors such as fat, age, and sex, with water content being approximately 60% in adults. Electrolyte balance is crucial, with sodium and potassium being key players; imbalances can lead to severe health issues.

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2. Functions of water in the body
• Transporting nutrients to cells and wastes from cells
• Transporting hormones, enzymes, blood cells
• Facilitating metabolism and cellular chemical functioning
• Acting as a solvent for electrolytes and nonelectrolytes
• Helping maintain normal body temperature
• Facilitating digestion and promoting elimination
• Acting as a tissue lubricant
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3. 3
Body Water Content
• Almost 60% of the body consists of water.
• Depends on
Body fat
 lean body mass →  water
 body fat (obesity) → water
Age
• Old age →  muscle mass + body fat → body water
Sex
• Male= muscle →  water
• Female = body fat → body water

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Body Fluid Compartments
• 2/3 of TBW is intracellular (ICF)
• 1/3 extracellular water
25 % interstitial fluid (ISF)
 8 % in plasma (IVF intravascular fluid)
2 % in transcellular fluids (third space)
• Synovial fluid, peritoneal fluid, pericardial fluid, intraocular
spaces fluid, cerebrospinal fluid, secretions of the digestive tract

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For 70kg adult male

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• Fluid compartments are separated by membranes that are
freely permeable to water.
• Movement of fluids due to:
Hydrostatic pressure
Osmotic pressure
 Hydrostatic pressure is the "pushing" force on water due to
the presence of more fluid in one region than another.
 Osmotic pressure is the "pulling" force on water due to the
presence of solutes in solution.

7. • Plasma-colloid osmotic (oncotic) pressure
Refers to the magnitude of the osmotic pressure exerted by
large molecules in solution.
Plasma proteins are of particular significance.
Normally ~ 26–28 mmHg.

8. Water Homeostasis
Daily intake of water:
• Water is added to the body by:
Ingested in the form of liquids or water in the food.
Synthesized in the body as a result of oxidation of
carbohydrates .
• Is highly variable among individuals depending on climate,
habits, and level of physical activity.

9. Daily loss of body water
• Water lost from the body by:
Insensible water loss
• Evaporation from the respiratory tract
• Diffusion through the skin
Fluid loss in sweat (physical activity, temperature).
Water loss in urine
Water loss in Feces

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Daily water
gain and loss

11. • Neutral water balance:- input = out put
• Negative water balance:- input < out put
 Dehydration
• Positive water balance:- input > out put
 Intoxication
Reading:
•Measurement of body fluid volume.
Water balance / homeostasis

12. • Body fluids are:
Electrically neutral
Osmotically maintained
• Specific number of particles per volume of fluid
• Homeostasis of fluid & electrolyte maintained by:
Ion transport
Water movement
Kidney function
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13. Composition of Body Fluids
• Body fluids contain
Electrolytes – charged ions
Non electrolytes – glucose
Colloid – protein
NB: Ionic composition of plasma and interstitial fluid is similar
(but higher concentration of protein in the plasma).

14. Regulation of body water
Sensors
•Hypothalamic osmoreceptors
Effectors
•ADH
•Thirst
Affecting
•Urine osmolality
•Water intake

15. Factors affecting ADH release
• Increase ADH
↑Osmolarity
↓ Blood volume
↓ Blood pressure
Drugs:
Morphine, nicotine,
cyclophosphamide
• Decrease ADH
↓Osmolarity
↑ Blood volume
↑ Blood pressure
Drugs:
• Alcohol, clonidine,
haloperidol

16. • Factors affecting thirst
Osmolarity
Blood volume
Blood pressure
Angiotensin
Dryness of mouth
Gastric distention

17. Fluid and electrolyte movement
• Osmosis – Fluid passes from areas of low solute concentration
to areas of high solute concentration
• Diffusion – tendency of solutes to move freely from areas of
high concentration to low concentration (down hill)
• Active Transport – requires energy to move through a cell
membrane from area of lesser concentration to one of greater
concentration
• Filtration – passage of fluid through a permeable membrane.
movement is from high to low pressure

18. Tonicity
• Refers to the osmotic pressure generated by impermeant solutes.
• Affect the fluid volume and pressure in a cell.
I. Hypotonic: Solution has a lower concentration of
nonpermeating solutes than the intracellular fluid (ICF).
II.Hypertonic: Solution has higher concentration of
nonpermeating solutes than the ICF.
III.Isotonic: Total concentration of nonpermeating solutes is the
same as in the ICF.

19. Effect of adding isotonic, hypertonic, and hypotonic solutions to the
ECF:

20. RBC in different media?

21. Edema
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• Edema is the accumulation of fluid within the interstitial spaces.
• Causes
 Increased hydrostatic pressure
 Lowered plasma osmotic pressure
 Increased capillary membrane permeability
 Lymphatic channel obstruction

22. • Hydrostatic pressure increases due to:
 Venous obstruction:
Thrombophlebitis (inflammation of veins)
Hepatic obstruction
Tight clothing on extremities
Prolonged standing
 Salt or water retention
Congestive heart failure
Renal failure
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• Decreased plasma osmotic pressure:
 ↓ Plasma albumin (liver disease or protein
malnutrition)
• Plasma proteins lost in :
 Glomerular diseases of kidney
 Hemorrhage, burns, open wounds and
cirrhosis of liver

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• Increased capillary permeability:
Inflammation
Immune responses
• Lymphatic channels blocked:
Surgical removal
Infection involving lymphatics
Lymphedema
Elephantiasis

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• Fluid accumulation: complications
 Increases distance for diffusion may impair blood flow
• Slower healing
• Increased risk of infection
• Pressure sores over bony prominences
 Edema of specific organs can be life threatening (larynx,
brain, lung)
 Water is trapped, unavailable for metabolic processes. Can
result in dehydration and shock.
 Psychological effect

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Electrolyte balance
• Na +
(Sodium)
90 % of total ECF cations
 ECF conc 135 -145 mEq / L
Pairs with Cl-
, HCO3
-
to neutralize charge
Low in ICF
Most important ion in regulating water balance
Important in nerve and muscle function

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Regulation of Sodium
• Renal tubule reabsorption affected by hormones:
Aldosterone: increase Na+
reabsorption.
Angiotensin II: increases Na+
& HCO3-
reabsorption.
ANP: increase Na+
excretion.

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Sodium imbalances
• Hypernatremia (high levels of sodium)
Plasma Na+ > 145 mEq / L
Due to ↑ Na + or ↓ water
Water moves from ICF → ECF
Cells dehydrate

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• Causes of hypernatremia:
Hypertonic IV solution.
Oversecretion of aldosterone
Loss of pure water
• Long term sweating with chronic fever
• Respiratory infection → water vapor loss
• Diabetes – polyuria
Insufficient intake of water (hypodipsia)

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Hyponatremia
• Overall decrease in Na+ in ECF
Plasma Na+ < 135 mEq / L
• Two types: depletional and dilutional
• Depletional Hyponatremia (Na+ loss):
Diuretics, chronic vomiting
Chronic diarrhea
Decreased aldosterone
Decreased Na+ intake

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• Dilutional Hyponatremia:
Renal dysfunction with ↑intake of hypotonic fluids
Excessive sweating→ increased thirst → intake of
excessive amounts of pure water
Syndrome of Inappropriate ADH (SIADH)
• Impaired renal excretion of water
Hyperglycemia – attracts water

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Potassium
• Major intracellular cation
• ICF conc. = 140-150 mEq/ L
• Functions
Regulates cellular enzyme activity and water content
Transmission of nerve and muscle impulses
Metabolism of proteins and carbohydrates
Regulation of acid-base balance by cellular exchange with H+

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Potassium imbalances
Hypokalemia
•Serum K+
< 3.5 mEq /L
•Causes:-
Decreased intake of K+
Increased K+
loss
• Chronic diuretics
• Acid/base imbalance
• Trauma and stress
• Increased aldosterone

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Hyperkalemia
• Serum K+ > 5.5 mEq / L
• Causes:-
 Renal disease
Massive cellular trauma
Insulin deficiency
Addison’s disease
Potassium sparing diuretics
Decreased blood pH

36. Calcium
• Calcium distribution
99% is found in the bones
0.7% located in ECF
0.1%-0.3% in side the cells
• Extracellular calcium exists in three forms
Potein bound (40%)
Complexed with citate, phosphate, sulfate (10%)
Ionized (50%)

37. Functions of Calcium:
•Neuronal excitability
•Muscle contractions
•Releases of hormones, enzymes and neurotransmitters.
•Blood clotting
•Bone formation
•Second messengers.

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Regulation of calcium:
•Parathyroid hormone
↑Blood Ca++
by stimulating osteoclasts
↑GI absorption and renal retention
•Calcitonin from the thyroid gland
Promotes bone formation
↑Renal excretion

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Calcium imbalances
Hypercalcemia
•Results from:
Hyperparathyroidism
Hypothyroid states
Renal disease
Excessive intake of vitamin D
Hypercalcemia of malignancy
• Tumor products promote bone breakdown
• Tumor growth in bone causing Ca++
release

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Hypercalcemia
• Usually also see hypophosphatemia
• Effects:
– Many nonspecific – fatigue, weakness, lethargy
– Increases formation of kidney stones and pancreatic stones
– Muscle cramps
– Bradycardia, cardiac arrest
– Pain
– GI activity also common
• Nausea, abdominal cramps
• Diarrhea / constipation
– Metastatic calcification

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Hypocalcemia
• Caused by:
Renal failure
Lack of vitamin D
Suppression of parathyroid function
Hypersecretion of calcitonin
Malabsorption

42. Hypocalcemia
• Diagnosis:
– Chvostek’s sign
– Trousseau’s sign
• Treatment
– IV calcium for acute
– Oral calcium and vitamin-D for chronic
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