Skin cells undergo mitosis constantly to maintain a layer of protection against infection, states UCSB ScienceLine. The outermost layer of skin is made up of dead skin cells that regularly fall off and need to be replaced.
People shed an average of 30,000 to 40,000 dead skin cells per minute, notes KidsHealth. Cells on the innermost layer of the epidermis replicate and slowly move toward the top layer of skin. This process results in a completely new epidermis every 35 to 45 days, explains Penn Medicine.
Skin forms an effective barrier against the outside world because the cells produce keratin, a tough protein also found in hair and calluses, according to UCSB ScienceLine. In addition to protecting against infection, skin also protects the body from ultraviolet rays from the sun, regulates temperature and produces vitamin D, states Penn Medicine.
Underneath the epidermis is a layer called the dermis. It is primarily made up of collagen and other fibers that provide support and flexibility to the skin system, according to Penn Medicine. The dermis contains nerve endings that allow people to feel temperature, texture and pain, states KidsHealth. It contains sweat glands, oil glands and blood vessels that supply oxygen and nutrients to the skin. Hair follicles are also found in the dermal layer, notes Penn Medicine.