国生 Stratum corneum 国上连 Brick and mortar model:the keratinized corneocytes ©Viable epidermis act as protein“bricks”embedded in a lipid“mortar” ·50-100um .May be the barrier of lipid drugs ©Dermis 0.3 to 4 mm in thickness There are numerous structures embedded within the dermis,including blood vessels,lymphatic vessels, nerve endings,hair follicles,sebaceous glands and sweat glands. 图生一 Process of Drug Absorption via Human Skin ④Skin appendages ·Eccrine sweat glands .Apocrine sweat glands et ·Hair follicles ·Sebaceous glands Less important for drug transport,as this route accounts for less than 0.1% of the total surface area of the skin. 国丝生一 国上人梦 neale Factors affecting percutaneous absorption ·Drug concentration ·Application area Semisolid dosage forms ·Aqueous solubility ·Lipophilicity ·Molecular weight ·Water content in skin ·Anatomical site ·Application time 22 Shanghai Jiao Tong University Stratum corneum Brick and mortar model: the keratinized corneocytes act as protein “bricks” embedded in a lipid “mortar” . Shanghai Jiao Tong University Viable epidermis • 50~100μm • May be the barrier of lipid drugs Dermis • 0.3 to 4 mm in thickness • There are numerous structures embedded within the dermis, including blood vessels, lymphatic vessels, nerve endings, hair follicles, sebaceous glands and sweat glands. Shanghai Jiao Tong University Skin appendages • Eccrine sweat glands • Apocrine sweat glands • Hair follicles • Sebaceous glands Less important for drug transport, as this route accounts for less than 0.1% of the total surface area of the skin. Process of Drug Absorption via Human Skin Shanghai Jiao Tong University Factors affecting percutaneous absorption • Drug concentration • Application area • Aqueous solubility • Lipophilicity • Molecular weight • Water content in skin • Anatomical site • Application time Semisolid dosage forms