Absorption, Distribution and Excretion of Pollutants Flashcards
Absorption definition
movement of toxins from the environment or site of administration into systematic circulation
primary routes of pollutant absorption
Gills
Gut
Skin/Epidermis
Gill absorption features for efficiency
high surface area
thin epithelial layers
high blood flow
Gut pollutant route
via food chains (contaminated prey, aquaculture feeds)
depends on species anatomy
feeding behaviour
gut chemistry (pH difference between marine and freshwater fish)
Skin pollutant absorption in Fish
variable skin histology including epidermis, dermis and scales
Skin pollutant absorption in Crustacea
absorption depends on the exoskeleton and moult cycle
what type of chemicals penetrate more easily through skin?
Lipophilic and small molecular weight compounds
Physicochemical properties affecting absorption
lipid solubility, molecular weight and pH sensitivity
target organ for Lipophilic compounds
Localise in fatty tissues
target organs for metals
Accumulate in gills, liver and kidney
Target organ for non-polar substances e.g. methyl mercury
Brain
Excretion in Gills
-non-polar, low molecular weight organics excreted via diffusion
-Metals are excreted via active transport or paracellular routes
Excretion in Kidney
removes compounds through filtration, ionization in urine and active secretion
Liver (Biliary) Excretion
processes large, polar or amphipathic substances
compounds are transported as bile or faeces
