7 Solutions/Solubility, Diffusion, Tension, & Fluid Physics

Solid, liquid, or gas dissolved in solvent Solute particles must be surrounded by solvent particles

Substance into which a solute is dissolved Dissolving agent Body fluid solvent = water

Homogenous mixture of two or more components Particles include atoms, ions, or molecules Solute dissolved in solvent Ex: Sugar and water (both polar)

Solution where the solute CANNOT be dissolved in the solvent Ex: Oil (non-polar) and water

Particles exist in solution somewhere between a TRUE solution and a TRUE suspension Size of particles - between those found in solutions and suspensions Mixed in way that remain evenly distributed w/out settling out

Polar dissolves in polar ↑ temperature ↑ solubility Heat (↑ temp) & energy (stirring) breaks intermolecular forces H2O dissolves polar substances better than ethanol d/t H2O more polar (dipole-dipole & hydrogen bonding) Solids - dissolution in solvent directly proportional to temp (100g dextrose in 100ml H2O will slightly displace volume d/t dextrose particles take up space b/w H2O molecules) ↑ temp ↑ solubility (solid in liquid) Gases - solubility dependent on solvent nature and temp ↑ temp ↓ solubility (gas in liquid) Endothermic & exothermic reactions

Solute grams per 100mL solvent = % solution Percent = per 100 0.9% NaCl = 0.9g NaCl / 100mL Molar solution - solute moles per 1L solvent NaCl = 23 + 35AMU = 58g/mol 0.9g NaCl / 100mL = 9g / 1L (9g/L) / (58g/mol) = 0.155 moles

Amount gas dissolved in liquid directly proportional to the pressure applied to the gas as it overlies the liquid Temperature also affects gas solubility (inversely proportional) 40mmHg pressure applied therefore 40mmHg pressure from gas molecules w/in the solution

Process by which substance spreads through the space available to it by random molecular motion Molecules more from area of high to low concentration Pressure gradient ∆P P1 - P2 > 0

Describes gas movement from one compartment to another through a porous membrane (diffusion) or small opening such as an orifice (effusion) Diffusion α 1/√Molecular Weight Directly proportional to solubility Larger, more cumbersome molecules = less diffusion

Diffusion coefficient = Gas solubility / √Molecular weight = Gas 1 Diffusion Rate / Gas 2 Diffusion Rate = (Gas 1 Solubility / Gas 2 Solubility) x (√Gas 2 MW /√Gas 1 MW) Given solubility - Gas A 20x more soluble than Gas B Relative rate of diffusion

Describes gas volume that diffuses across membrane per minute Diffusion rate = (Area x Diffusion coefficient x ∆P) / Membrane thickness r/t alveolar capillary membrane ↑ surface area ↑ diffusion ↑ thickness ↓ diffusion

Density more important Influences probability that interactions b/w fluid molecules will occur ↑ density = ↑ molecules per unit area therefore ↑ change molecular collisions ↑ drag (resistance) ↓ flow

Diffusion - porous membrane; gradual gas mixing d/t motion of component particles Effusion - escape of gaseous molecules via small opening (orifice) into evacuated space α 1/√MW α 1/√Density Less dense gas ↑ diffusion/effusion

Gas volume in liquid unit at 0°C and 760mmHg Expressed as numerical value for particular gas in given liquid = mL gas per 1 mL H2O

Defined as ratio of gas volume absorbed to the solvent volume at body temp 37°C and ambient pressure Used to express the blood/gas and tissue/gas ratio “Blood-gas partition coefficient”

Defines the pressure gradient across the wall of sphere (alveoli) or cylinder (blood vessels and airway) which are r/t surface tension and radius

Tension defined as internal force generated by structure Sphere T = (P x r) / 2 Cylinder T = P x r Pressure inversely proportional to the radius P α 1 / r Small vs. large alveoli pressure gradient w/out surfactant

Amphipathic detergent Produced by Type II alveolar cells Equalizes pressures w/in small and large alveoli Surfactant present in alveoli to ↓ surface tension d/t ALI Increased efficacy in smaller radius alveoli (well-organized structure/orientation)

Created at the interface (ALI) b/w liquid and gas where liquid molecules are pulled together by intermolecular (cohesive) forces Air non-polar and H2O polar Pel 2/3 surface tension and 1/3 elastic intrinsic factors (type, number, health of fibers) Know relationship to surfactant

Aggregate of surfactant molecules dispersed in liquid forming a colloidal suspension Hydrophilic (polar) head in contact w/ solvent and hydrophobic (non-polar) tail w/in micelle center

Laminar flow F = (π ⋅ r^4 ⋅ ∆P) / (8 ⋅ η ⋅ L) F = ∆P / R Directly proportional to ∆P and r^4 Inversely proportional to viscosity and length Resistance opposite (inverse to r^4 and direct to viscosity and length) R α 1 / r^4 ↓ viscosity ↑ flow Application: 18G vs. 24G (diameter), increased hydrostatic pressure (∆P), polycythemia/anemia (viscosity) impact on flow

Predicts when flow through tube changes from laminar to turbulent (Inertial Forces)/(Cohesive Forces) < 2,000 Laminar Flow 2,000-4,000 Transitional > 4,000 Turbulent Flow Re = (velocity ⋅ diameter ⋅ density)/viscosity Does not consider or predict resistance

Reynolds number > 4,000 High flow of velocity Tube narrows or kink/bend/angle Roughness on tube wall (mucus, clot, etc.) Fluid flows through an orifice Resistance to flow increases when turbulent Density determines turbulent flow (not viscosity)