body fluids lectures

60% water

in the human body

83% water

in human blood

Electrocyte concentrations & Pressure gradients

Water distribution maintained by

gradient pressure

presence of albumin + electrolytes define the

intracellular fluid (ICF) compartment

67% of total body water

extracellular fluid (ECF) compartment

33% of the total body water

25 % of ECF

intravascular compartment (blood vessel + lymph)

75% of ECF

extravascular compartment

interstitial and transcellular fluid

Extravascular compartment of ECF is further divided into

Interstitial fluid

appproximately 95% of the extravascular compartment; directly bathes the cells and tissues in the body

transcellular fluid

appproximately 5% of the extravascular compartment; separated from the plasma by an additional epithelial layer + capillary endothelium

=

Water loss rate ____ water intake rate

Cations (+)

sodium and potassium

Anions (-)

chloride and bicarbonate

Electrolytes functions

Regulates water distribution, osmotic pressure, nerve transmission to muscles, cell permeability, oxidation-reduction rxns, maintenance of blood pH

sodium, chloride, & bicarbonate

Plasma and interstitial fluid have high levels of

potassium

Intracellular fluid has high levels of

Osmosis

diffusion of solvent molecules from high to low CG

Osmotic pressure

physical force exerted during osmosis

isotonic

solute concentration = water concentration (both in/out of cell; equilibrium)

hypotonic

lower solute concentration outside cell OR water concentration larger w/in cell (swell)

hypertonic

higher solute concentration outside cell OR water concentration smaller w/in cell (shrink)

Anion Gap

Test to examine electrolyte balance in relation to acid-base status

[Na+ + K+] – [Cl- + HCO3-]

equation for anion gap

4 to 12 mEq/L

normal range of anion gap

High level of anion gap

patients with ACIDOSIS due to kidney disease, diabetes mellitus (ketoacidosis), or aspirin and methanol poisoning

Low level of anion gap

instrument error and must be investigated by the instrument operator

hypoalbuminemia

if low level of anion gap is true

sodium

90% of plasma cations

Absorption of sodium

causes a temporary increase in extracellular fluid volume

ATP pump

exchange sodium for potassium

3

_ Na+ per efflux

2

_ K+ per influx

10 times

sodium concentration outside is _________ that inside the cell

Aldosterone

influences sodium reabsorption in kidneys + accelerates exchange of sodium & potassium

Atrial natriuretic peptide (ANP)

hormone secreted by heart to excrete sodium = decrease BP

heart

releases ANP to decrease pressure on itself; water will follow wherever sodium is excreted to

Hyponatremia

common; decreased sodium (Low sodium intake, diarrhea, prolonged vomiting, sweating due to fever, or renal disease)

Hypernatremia

less commmon; increased sodium (severe dehydration, Cushing syndrome, inappropriate saline solution therapy, and ingestion of high- sodium foods w/ low water intake (super excretion of H2O compared to sodium)

diarrhea

super excretion of sodium compared to water

Ion-selective electrodes (ISEs)

Sodium electrodes have a glass membrane that allows Na+ ions to flow into tip of the electrode, where they interact w/ the measuring & reference electrode wires

source of error for ISEs

diluted samples are sensitive to high lipid/protein content, which displace fluid to read sodium

Potassium (K+)

Most abundant cation and mostly (98%) in intracellular fluid

equals

Daily potassium intake __ daily potassium excretion

aldosterone

what controls K+

Hypokalemia

Decreased level of potassium; Caused by low intake (of potassium), vomiting, diarrhea, gastrointestinal problems, diuretic use, and irregular heartbeat palpitations

Hyperkalemia

Elevated blood potassium level that results when potassium leaves cells faster than it can be excreted by the kidneys (Paralyzes heart muscles along with blocking of aldosterone activity)

Chloride

Anion of highest extracellular concentration; moves passively with sodium

inverse

Chloride has an _____ relationship with bicarbonate, ensuring electrical neutrality

Chloride shift

when blood contains O2, chloride shfits from RBCs to plasma + bicarbonate shifts from plasma to RBCs; opposite when CO2 is present in blood

carbonic acid

CO2 is converted into __________ and can also be picked up by hemoglobin

H+ and bicarbonate

Carbonic acid is a weak acid that can easily dissociate into ________

chloride

Because charged anions cannot cross membranes (polar molecules), H+ is picked up by hemoglobin and bicarbonate is exchanged with ___________

reversed

for CO2 to exit the body, process/chloride shift is

Chloride function

Determines osmotic pressure, acid-base balance, O2 and CO2 exchange in RBCs

Chloride location

Extracellular fluids (serum, plasma, cerebrospinal fluid, tissue fluid, and urine); Does not enter cells, except for RBCs

Hypocholermia

Decreased level of chloride in plasma (Caused by many metabolic acidosis syndromes, diabetic ketoacidosis, renal disease, vomiting or intestinal blockages)

Hypercholermia

Increased level of chloride in plasma (Caused by dehydration, renal tubular acidosis, prolonged diarrhea, and diabetes insipidus)

Bicarbonate

Anion of highest extracellular concentration; Makes up 90% of the CO2 dissolved in blood

Forms of bicarbonate

dissolved CO2, CO2 bound to amine groups in protein, ionic form, and carbonic acid (4 FORMS)

increased bicarbonate values

Metabolic alkalosis, compensated respiratory acidosis, and a large potassium deficiency accompanied by alkalosis

decreased bicarbonate values

Metabolic acidosis and compensated respiratory alkalosis

Colligative properties

solute particles:solvent molecules in solution ratio (Not based on the identity if the solute or solvent)

Osmolality

number of solute particles per unit of solvent (concentrated samples have high osmolality & diluted samples have low osmolality)

Influence of ADH

When blood osmolality increases, the hypothalamus stimulates ADH secretion to cause thirst and increases water resorption through the kidney

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Excessive ADH secretion leads to resorption of body water, diluting the blood, making it hypo-osmotic

Diabetes insipidus

ADH deficiency; kidneys cannot resorb water, tremendously diluting urine, and blood contains little water, making it hyperosmotic

freezing point depression

easiest & cheapest way to measure osmolality

arteries & veins

most fluid is carried through

Lymph fluid

capillaries with leaky endothelial cells give blood contained with protein, bacteria, and cancer cells

Edema

excess fluid in lymphatics system (imbalance of hydrostatic pressure vs. colloidal osmatitc pressure)

Transudate edema

low amounts of protein, few cells, and high-water content (high hydrostatic pressure and low osmatic pressure)

Exudate edema

Fluids that contain a high-protein, high cells (inflammatory reaction or lymph system blockage (i.e., lymphedema)

transudate

Increased hydrostatic pressure in vessels + Decreased plasma osmotic pressure

exudate

Increased vascular permeability + Decreased lymphatic effectiveness