Lecture 14: Body fluids- Exam 3 Flashcards
Osmolarity and Osmolality
Osmolarity: Osmole/Liter
Osmolality: Osmole/Kg
What is an effective osmole?
Refers to substances that does not easily cross membrane
Offers an osmotic force for water.
Daily intake of water
Ingestion (Fluids and food): 2100 mL/day
Metabolism: 200 mL/day
Total: 2300 mL/day
Daily outtake of water
Insensible evaporation:Skin-350 mL/day ( 3-5L/day for severe burns), Lungs-350 mL/day
Feces-100 mL/day
Sweat- 100 mL/day (5000 mL/day during exercise)
Urine-1400 mL/day
Total- 2300 mL/day
Distribution of body fluids in body
Total body water: 42 L (50% weight in female, 70-75% weight in premature and newborn)
Intracellular:28.0L
Extracellular: 14.0L (Plasma:3.0,interstitial fluid: 11.0)
BMP (Basic Metabolic Profile)
Level of cations, and anions in extracellular
Does not reveal disease
Necessary for osmolar gap
Osmolar gap
Helps to narrow differential diagnosis
Difference between measured osmolality and estimated osmolality
Normal
Substances than elevate osmolar gap
Methanol ethanol ethylene glycol Mannitol acetone
Plasma and Interstitial fluid
capillaries separates both compartments
Capillaries highly permeable to ions causes similar ionic composition
Capillaries have a low permeability to proteins which causes higher concentrations of proteins in plasma
Intracellular fluid composition
Almost no calcium ions
Small amounts of sodium and chloride
Moderate amounts of magnesium and sulphate ions
Large amounts of potassium and phosphate ions
Indicator dilution principle
Applies to measurement of fluid volume in body fluid compartments
Requirements for an indicator
Disperses evenly throughout membrane
Disperses only in compartment being measured
Not metabolized or excreted
Not toxic
Volume B= Volume A X Concentration A/ Concentration B
Fluid distribution and amounts
Amounts of extracellular fluid in interstitial spaces and plasma determined by balance of hydrostatic and colloid forces across capillary
Distribution of fluid between intracellular and extracellular compartments determined by osmotic effects primarily sodium and chloride ions.
Potential osmotic pressure of a solution
1 mosm–>19.3 mm Hg
80% of total osmolarity of the interstitial fluid and plasma is due to sodium and chloride ions
For intracellular fluid half of the osmolarity is due to potassium ions
Addition of isotonic saline o extracellular fluid
Increases volume of extracellular fluid
osmolarity remains the same
Addition of hypotonic saline to extracellular fluid
Increases volume of both compartments
Decreases osmolarity in both compartments
Addition of hypertonic saline to extracellular fluid
Increases volume of extracellular fluid
Decreases volume of intracellular fluid
Increases osmolarity of both compartments
Anatomical organization of kidney
Capsule Renal cortex (Bowman's capsule, Proximal and distal convoluted tubules) Renal medulla (renal pyramids) Renal pelvis (minor and major calyces)
Structure of nephron
8,00.000-1 million nephrons/kidney
Decrease by 10% every year after the age of 40
Each large collecting duct(250/kidney) receive urine from about 4000 nephrons
Cortical nephrons have glomeruli in outer renal cortex and possess short loop of Henle
Juxtaglomerular nephrons have glomeruli deep in renal cortex and possess long loop of Henle
Percentage of blood received by kidney
Kidney receives 22% of total cardiac output (1100mL/min)
Regulation of hydrostatic pressure in capillaries
Efferents arterioles help regulation in both set of capillaries
High hydrostatic pressure in glomerular capillaries(=60 mm Hg) causes rapid fluid filtration
Low hydrostatic pressure in peritubular capillaries (=30 mm Hg) causes rapid fluid reabsorption
Blood flow to and from kidney
renal artery->interlobar arteries->arcuate arteries->interlobular arteries->afferent arterioles->glomerular capillaries->efferent arterioles-peritubular capillaries->interlobular veins->arcuate veins->interlobar veins->renal veins
