Izvorni znanstveni članak
Skin aging is a multisystem degenerative process that involves the skin and skin support system. Young faces tend to be convex with full lips, sweeping jaw line with full temples and cheeks. Aged face tends to be concave with flat lips, sunken temples and cheeks, scalloped mandible and more shadows. Aging caused by the genes we inherit and depending on the passage of time per se is called chronological or intrinsic aging. Intrinsic akin aging is characterized by atrophy of the skin with loss of elasticity and slowed metabolic activity. The signs of intrinsic aging are fine wrinkles, thin and transparent skin, loss of underlying fat, facial bone loss, dry skin, inability to sweat sufficiently to cool the skin, hair loss and unwanted hair. The other type of aging is known as extrinsic aging and is caused by environmental factors. Among harmful environmental factors that contribute to extrinsic aging, long-term effects of repeated exposure to ultraviolet light are most significant and are referred to as photoaging. It is a cumulative process and depends primarily on the degree of sun exposure and skin pigment. UV irradiation invokes a complex sequence of specific molecular responses that cause damage to the skin connective tissue. Photoaging affects the sun-exposed areas and is characterized clinically by fine and coarse wrinkling, roughness, dryness, laxity, telangiectasias, loss of tensile strength and pigmentary changes. There is also an increase in development of benign and malignant neoplasms on photoaged skin.
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