Final answer:
Muscles are not affected by exposure to salon products as they are not composed of epithelial tissue, unlike the epidermis, hair, and nails which can absorb harmful substances.
Step-by-step explanation:
Extended exposure to salon products without proper precaution can affect all of the epithelial tissues except muscles. This is because muscles are not made of epithelial tissue but consist mainly of muscle tissue that is structurally and functionally distinct from the epidermis which is the outermost tissue layer of the skin, hair follicles, and nails, which are considered accessory structures of the skin.
The epidermis, hair, and nails are composed of dead keratinized cells, and these tissues can be affected by harmful chemicals found in salon products. In contrast, the muscle tissue does not have the same exposure or absorption properties with respect to salon products, making it the one group of tissues among the options listed that would not be affected.