= mvmt of a fluid through a semipermeable membrane from HIGH pressure area LOW pressure Hydrostatic Force = the mechanical force of water pushing against cellular membranes In vascular system hydrostatic pressure = the blood pressure pushing against vascular walls. Colloid Osmotic Pressure = tendency of plasma proteins to hold water in the intravascular spaces (maintains water in ECF) Albumin is the plasma protein which exerts the greatest osmotic pressure o Albumin is formed in the liver o Most abundant plasma protein o Binds to hormones and transports them o Acid-base balance Globulin o Antibodies (IgG) o Humoral immunity o Transport of iron and fats Fibrinogen o Blood coagulation/clotting cascade Osmolality = a measure of the concentration of molecules per kilogram of water ( mOsm/kg – weight measurement) *PREFERRED measure of osmotic activity in clinical assessment Indicates hydration status, body fluid concentrations Can measure serum or urine osmolality Normal osmolality = 285-295 mOsm/kg Osmolality = 2 (Na) + K + BUN + Glucose 3 18 Osmolarity = a measure of the concentration of molecules per liter of solution ( mOsm/L ) NOTE: Difference btwn osmolality and osmolarity matters what types of solutes you are measuring o Na & K vs. proteins, glucose lipids present also Tonicity = describes the “effective” osmolality of a solution (term interchangeable with osmolality !!) ISOtonic Solutions – has the SAME osmolality as the ECF 2
Patho Wk 5: Ch. 3 Examples o D5W Distributes evenly in the body compartments Used to replace deficits of total body water o Normal Saline (0.9% NS) NOTE: Each liter adds ¼ liter to ECF & adds ¾ liter to interstitial fluid HYPERtonic Solutions – have a HIGHER concentration of solute and are MORE CONCENTRATED than ECF Examples o 3% saline o 5% saline Net movement (PIC) = ICF ECF HYPOtonic Solutions – have a LOWER concentration of solute and are MORE DILUTE than ECF Examples o 1/2 NS o 1/4 NS Net movement (PIC): ECF ICF THIRST = A desire for water Regulated by osmoreceptors in the hypothalamus Angiotensin II plays a role Symptom: Dryness of the mouth CAUSES: O d OSMOLARITY Hypertonicity occurs (Na+ higher) Water is drawn from the cell ( crenation ) Water is ingested Cell returns to normal O d FLUID VOLUME Loss of fluid (ex – hemorrhage) d circulation (CHF: H2O moves from ICF to ECF – look swollen but actually depleted) Dryness of the mouth Thirst triggered replace fluids resolves ALTERED THIRST MECHANISMS: o Coma – don’t know they’re thirsty o Senility (dementia), Psychosis, Confusion – can’t comprehend thirst o Psycogenic Polydipsia – drink way too much water water intoxication, hypoNa+ REGULATION OF BODY FLUID KIDNEYS!! (review in book) Filtration – r/t hydrostatic pressure Secretion – Mvmt from blood to renal tubules Reabsorption – Mvmt from renal tubules to the blood Excretion - Mvmt from kidney to the environment KIDNEYS how well are they working?
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- Fall '17
- Regina Urban
- ECF, Diuretic, Calcium metabolism