Lecture 1: Body Fluid Compartments Flashcards
Extracellular fluid makes up what % of body water?
42 L of body water in average person.
14 L = Extracellular fluid (~40% of body water)
-Interstitial fluid= 11 L (75% of extracellular fluid)
-Blood plasma= 3 L (25% of extracellular fluid)
Intracellular fluid makes up what % of body water?
42L of body water in average person.
28 L = Intracellular fluid (~60% of body water)
What makes up the transcellular fluid compartment?
synovial, peritoneal, pericardial, and intraocular spaces, CSF. (combined = 1-2 liters)
All considered aspecialized type of extrcellular fluid.
Plasma and interstitial (both extracellular fluids) are similar in what ways?
- Highly permeable capillary membrane
- Protein level > in plasma because of low membrane permeability.
Intracellular fluid is different from extracellular fluid in what ways?
- Intracellular fluid is separated by a cell membrane
- Highly permeable to water, not electrolytes (semi-permeable to electrolytes)
Which ions are predominently found in extracellular fluid (plasma and interstitial fluids)?
Proteins HCO3 Cl- CA++ Na+
Which ions are predominently found in intracellular fluid?
K+
Mg++
Phosphate
Cells contain large amounts of protein, almost 4 times as much as in the plasma Guyton Hall p. 287
What is the Donnan effect?
Effects the Extracellular fluids.
The concentration of + ions is slightly greater in he plasma than the interstitial fluid because the protein in the plasma has a net negative charge and attracts cations (Na and K).
Negatively charge ions tend to be slightly greater in the interstitial fluid due to repelling of - charged ions from the negatively charged plasma proteins.
For practical purposes, the concentration of ions in the interstitial fluid and plasma are considered about equal.
Osmol
1 osmole (osm)= 1 mol (6.02 x 10*23) Total number of particles in a solution
mole= specific quantity of molecules.
Molecules (mols) which contain more than 1 particle dissociate into separate inos when dissolved in solution (osmol)
1 mol of NaCl=>dissolve into solvent (1 L)=> concentration of 2 osmol/L solution (Na<=>Cl)
osmolality:
osmoles/Kg of water
osmolarity:
osmoles/Liter of solution
Normal body osmolarity:
285 mol/L
Osmosis:
-the net diffusion of water across a selective membrane
(High water concentration to low water concentration)
Water follows sodium
Osmotic Pressure:
the amount of pressure required to prevent osmosis
pressure applied in opposite direction of osmosis
1 mOsm gradient change=
19.3 mmHg osmotic pressure
Osmotic pressure of a solution is proportional to the concentration of osmotically active particles
80% of interstitial fluid and plasma osmolarity is due to :
Sodium & Chloride ions
Plasma is 1 mOsm/L >interstitial fluid
(plasma proteins maintain 20mmHg greater pressure in capillaries than surrounding tissues.)
50% of Intracellular osmolarity is due to :
Potassium ions
The total osmotic pressure at 37*C in plasma, interstitial, and intracellular fluids differ how?
Plasma osmotic pressue (5443) is 20mmHg greater than the osmotic pressue of interstitial and intracellular which are equal (5423).
What happens to a red blood cell placed in hypotonic solution?
Swells; takes in water
What happens to a red blood cell placed in hypertonic solution?
Shrinks; gives up water
Causes of hyponatremia:
- excessive water
- loss of sodium
Conditions: Diarrhea and vomiting diuretic abuse Addison's disease excessive water retention (ADH)
Causes of Hypernatremia:
- Loss of water
- Excess sodium
Conditions: Lack of ADH Diabetes insipidus Dehydration Aldosterone secretion
edema
Excess tissue fluids
Occurs mostly in extracellular fluid compartment
Intracellular edema can occur in certain conditions:
- Inflammation has a direct effect on increasing cell membrane permeability
- depression of cellular metabolic function
- lack of nutrition to the cells: decreased blood flow and reduced oxygen & nutrient supply
- ionic pumps of cell membrane require oxidative metabolism (ATP) to remove intracellular sodium
