The skin is the largest organ in the body. It protects the body from physical injury, temperature regulation, sunlight, infections, stores water, fat, and plays a key role in metabolism, including vitamin D, among other functions. The skin is made up of three main layers, epidermis (upper or outer layer), dermis (lower or inner layer) and subcutaneous tissue. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Skin cancer begins in the epidermis, which is composed of three types of cells: keratinocytes, melanocytes, and Langerhans cells. Keratinocyte cells are found in the deepest basal layer of the stratified epithelium that comprises the epidermis. They have the task of producing the protein keratin and making the skin waterproof and resistant. Keratins form the cytoskeleton of keratinocytes and are what make up our hair and nails. Therefore, if defects in the expression of keratin occurred, numerous diseases of the epidermis, hair and nails would occur. As they mature, divide and differentiate, they lose water, flatten and move into the most superficial layer of the epidermis, the stratum corneum, which accumulates mainly dead keratinocytes, keratins and lipids. This is the tough outer layer of the skin. The skin completely renews itself every 3-5 weeks by replacing the accumulated dead keratinocytes with others. Keratinocytes also play a role in the immune system as immunomodulators, activating Langerhans cells in response to injury, preventing the penetration of unwanted substances into the skin, and secreting inhibitory cytokines in the absence of injury. Other significant cells in the epidermis are melanocytes, cells that produce melanin, the pigment responsible for skin tone and color and present in the lower part of the epidermis. The dermis is undoubtedly the most important layer for the maintenance of the skin and hair follicle. It contains cells for the immune system, collagen, elastin, fibronect which keeps it soft and elastic and proteins which allow water absorption to keep the skin hydrated and with a good texture. Please note: this is just a sample. Request an article customization now from our expert writers. Get a Custom Essay The dermis also contains capillaries (tiny blood vessels) and lymph nodes (depots of immune cells) blood vessels carry oxygen and nutrients, and lymph nodes to protect it from microorganisms The dermis receives blood and distributes it to the epidermis, regulates temperature, wounds and eliminates toxins. The subcutaneous tissue is the innermost layer of the skin located under the dermis made up of connective tissue and fat molecules. Together with the connective tissue, it connects the dermis with the muscles and bones. Works Cited Wolff, K., Johnson, R. A., Saavedra, A. P., & Roh, E. K. (2017). Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology (8th ed.). McGraw-Hill Education.Kumar, V., Abbas, A. K., Aster, J. C., & Robbins, S. L. (2019). Robbins Basic Pathology (10th ed.). Elsevier.James, W.D., Berger, T.G., & Elston, D.M. (2020). Andrews Skin Diseases: Clinical Dermatology (13th ed.). Elsevier.Rigel, D.S., Robinson, J.K., & Ross, M.I. (2019). Skin cancer. In K. D. Mann, L. E. Benveniste, J. S. Cooper, A. N. Hata, & S. G. Patel (Eds.), Abeloff's Clinical Oncology (6th ed., pp. 1799-1825). Elsevier.National Cancer Institute. (2021). Skin cancer (including melanoma): patient version. https://www.cancer.gov/types/skinKim, R.H., Armstrong, A.W., & Harpole, D.H. (2016). Cutaneous melanoma. In C. A. Pautler & R. T. Chung (Eds.), Current Diagnosis and Treatment: Gastroenterology, Hepatology, and Endoscopy (3rd ed.,.