Principles+Lec+3+2013

Skin dermal route function protect against external

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Unformatted text preview: rier for things to not get through 1. Skin: “Dermal Route” Function: ‘Protect against external environment’ Characteristics of the Epidermis: ‘Thick Lipoidal Barrier’ A. “Stratum corneum” keratinized (1o barrier) Thickness varies less cell layers means more absorption B. No pores since cells are dead, they have no pores tight intercellular junctions, therefore paracellular C. Tight intercellular junction (this adds an additional level of control) D. No transport systems (Diffusion mediated) E. Low blood flow (Low in Epidermis, Higher in Dermis) no nutrients going to top layer • Lower layers contain non-selective aqueous diffusion media • Diffusion mediated but much less effective! 1. Skin: “Dermal Route” Is this a significant route of absorption? YES!! Hydrophobic (fatty) compounds Hydrophilic compounds Can be absorbed (slowly) No not by diffusion Diffusion Mediated! Therefore absorption will be based on the limitations of this method (size, concentration gradient, surface area etc) ALSO: Access through dermal appendages! hair folicles, sweat glands, etc. compounds to this allows some hydrophilic pass through - less than 1% of total S.A - more rapid passage - Hydrophilic substances can use this route hydrophilic compounds CAN get through, but its very difficult Other Access has many glands, blood tissues, etc. high blood flow and favourable concentration gradient Other Access • Dermis has various access points • Glands • Hair follicles • Physical Breaks in continuous outer “shell” a lot of fat stores, lipophilic compounds get stuck here for a while and entre the blood stream late • High blood flow •Take away absorbed toxins: favorable equilibrium • Fat stores •“like dissolves like” Increasing Dermal Absorption • Dermal absorption is increased by: hydrating the surface of your skin increases dermal absorption • Hydration (provide aqueous media, cell swelling), increase 10X • Solvent effects (DMSO can alter lipids in membrane) • Temperature (increase temp, increase blood flow) • Amount of dermal appendages Species % Absorbed of (2,4-D) DMSO can increase rate of dermal absorption by breaking down some of the fats and making skin more pores Rat 20 h...
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