Completed notes of the course Part 2

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TECHNOLOGIES FOR REGENERATIVE MEDICINE 2 Integumentary experience The integumentary system is the largest organ in our body. It accounts for 15-20% of the total body mass. It is formed by: skin layers, glands (sebaceous, sweat, mammary), blood vessels and nerves, the cornea, hair and nails. The skin interfaces our body with external environment. The vital functions played by the skin are: • barrier to physical (mechanical, radiation), chemical and biological (pathogens) agents; • homeostatic: prevents dehydration and regulates body temperature, • sensory: touch (position), pain and pleasure sensitivity; • metabolic: converts precursors molecules to vitamin D within the metabolism of calcium; • secretory: lubricant for hair, communication hormones (pheromones), sweat. The main cell populations present in the skin are: keratinocytes in the epidermis, which are highly immunogenic, fibroblasts in the dermis which are moderately immunogenic, dendritic cells (DCs) which are antigen-presenting cells of the immune system, their main function is to process antigen material and present it on the cell surface to the T cells of the immune system, they act as messengers between the innate and the adaptive immune system. Following skin injury, a process called epidermal cross-talk takes place: 1. the platelets adhere to the collagen of the ECM; the fibrinogen secreted by the liver cells binds to the thrombin present on the platelets to form fibrin, which aggregates the blood clot; the clot serves as a scaffold for infiltration of the other cells in the area (macrophages, neutrophils, T lymphocytes and platelets). 2. Petri-lesional keratinocytes release interleukine-1 (IK-1) and tumor necrosis factor 𝛂 (TNF- 𝛂) that recall cells of the immune system and fibroblasts that form the…