Study Unit 1 Flashcards
4 Ways that the body loses water daily
- Insensible Water loss
- Fluid loss in sweat
- Water loss in Feces
- Water loss in Kidneys
Transcellular fluid
the portion of total body water contained within the epithelial-lined spaces and forms part of the extracellular fluid
Hematocrit
The fraction of the blood composed of red blood cells determined by a centrifuge
Normal ranges:
Men ~ 0.40
Women ~ 0.36
Extracellular fluid constituents
Cations:
- Sodium (Na+)
Anions:
- Chlorine (Cl-)
- Bicarbonate (HCO3)
Intracellular constituents
Cations:
- Potassium (K+)
- Magnesium (Mg2+) and Calcium
Anions:
- Organic Phosphates (PO4) like ATP and ADP
- Protein
Cation concentrations inside and outside the cell
Extracellular:
- Na+ = 140 mEq/L
- Mg++ and Ca++ = 7 mEq/L
- K+ = 10 mEq/L
Intracellular:
- Na+ = 15 mEq/L
- Mg++ and Ca++ = 18 mEq/L
- K+ = 145 mEq/L
Osmosis
- Netto diffusion of water from an area with a high water concentration to an area with a lower water concentration across a selectively permeable membrane
- Netto diffusion of water from an area with a low solute concentration to an area with a high solute concentration across a selectively permeable membrane
Osmolality
Osmolal concentration expressed as osmoles per kilogram of water
Osmolarity
- Osmolal concentration of a solution expressed as osmoles per liter of solution
- every molecule dissolved in the TBW contributes, regardless of size, weight, charge or composition
Moles
A unit of measurement that represents the amount of a substance, typically a solute, in a solution
n= m/M
Osmoles
- A unit of measurement that that represents the amount of a substance that dissociates in water to create an osmotic pressure
- the osmosis caused by a mole
Moles vs Osmoles
A “mole” is a unit measuring the amount of a substance, representing a specific number of particles (Avogadro’s number), while an “osmole” is a unit that represents the number of particles that contribute to the osmotic pressure of a solution, meaning it takes into account the dissociation of a compound when dissolved in water; essentially, one mole of a fully dissociated compound would equal the same number of osmoles as the number of particles it breaks into when dissolved.
Osmotic pressure
- the precise amount of pressure necessary to prevent osmosis
- high osmotic pressure = lower [H2O] and higher [solute]
- directly proportional to the [osmotically active particles] regardless of size
Tonicity of solution
depends on [solute] in relation to the ICF
Hyponatremia-dehydration causes
- diarrhea
- vomiting
- overuse of diuretics
- Addison’s disease (insufficient aldosterone)
Hyponatremia-overhydration causes
- Syndrome of Inappropriate ADH (SIADH)
- bronchogenic tumors
Hypernatremia-dehydration
- diabetes insipidus (lack of ADH)
- excessive sweating
- renal disease (kidneys are unresponsive to ADH) called “nephrogenic” diabetes insipidus
Hypernatremia-overhydration
- excessive secretion of the sodium-retaining hormone aldosterone
- primary aldosteronism
- Cushing’s disease (cortisol causes the kidneys to retain sodium and excrete potassium)
Consequences of Hyponatremia
Rapid hyponatremia:-
cell swelling, especially in the brain cells
- brain cell edema
Symptoms:
- headache
- nausea
- lethargy
- disorientation
[sodium] < 115-120mmol/L: seizure, coma, herniation, permanent brain damage, death
Chronic hyponatremia:
- cannot be treated with hypertonic solution, as this may lead to demyelination
Intracellular edema
- hyponatremia
- depression of the metabolic systems of the tissues
- lack of adequate nutrition to the cells
- Inflammation
Extracellular edema
- abnormal leakage of fluid from the plasma into the interstitial fluid
- failure of the lymphatic system to return fluid from the interstitial fluid back into the plasma (lymphedema)
This is primarily caused by excessive capillary fluid filtration
Edema caused by Heart failure
- Increased venous and capillary pressure: increased capillary filtration
- decreased arterial pressure: decreased excretion of salt and water by the kidneys, increasing edema
- decreased blood flow to the kidneys: increased renin secretion, angiotensin II formation, and aldosterone secretion. This leads to increased water retention by the kidneys
Edema caused by decreased kidney excretion of salt and water
- NaCl remains in the ECF
- High volumes NaCl & H2O in ECF
- leaks from blood into the interstitial fluid
- widespread increases in interstitial fluid volume (extracellular edema)
- Hypertension because of the increase volume
Edema caused by decreased plasma proteins
- decreased plasma colloid osmotic pressure
- capillary filtration and extracellular edema
- nephrotic syndrome:
- damage to the membranes of the renal glomeruli
- plasma proteins leak into the urine
- loss exceeds the body’s ability to synthesise new plasma proteins - cirrhosis of the liver:
- large amounts of fibrous tissue along the liver parenchymal cells
- failure of cells to produce sufficient plasma proteins - ascites:
- liver fibrosis compresses the abdominal portal venous drainage vessels
- raises capillary hydrostatic pressure in the gastrointestinal area
- increased filtration of fluid out of the plasma
