The largest organ of the body in terms of surface area and weight, covers
all the external surface of the body. Acts as protective barrier to the environment,
allowing and limiting the inward and outward passage of water, electrolytes and various
Skin aging is a biochemical process that principally takes place in the lower epidermis and in the dermis. It can be intrinsic or chronological aging and extrinsic or environmental aging.
Various environmental factors ,UV-irradiation, air pollution, smoking, poor diet, alcohol, dry weather and stress are responsible for extrinsic aging. Among them UV-irradiation is the most fundamental one, as it can damage skin to such an extent, that makes it seem prematurely aged (photoaging). Photoaging is the main cause of wrinkles.
Aging is the consequence of lower production and increased breakdown of the proteins, collagen and elastin, that impart firmness and elasticity to the skin. Protein glycation, a non-enzymatic reaction of proteins( collagen and elastin), results in cross-linked proteins called AGE (Advanced Glycation End-products), responsible for deterioration of the existing collagen and elastin .UV radiations accelerates normal aging by promoting glycation through oxidative stress.
Major contributing mechanism in aging is the Reactive oxygen species(ROS), initiating and activating a complex cascade of biochemical reactions in human skin, thus interfering with the synthesis of dermal collagen. Also have direct damaging effects on membrane lipids like ceramides
Ceramides constitute about 40% of stratum corneum. The amount of ceramides present in the stratum corneum decreases drastically with age because keratinocytes have a reduced ability to synthesize ceramides over time. Reduced production of ceramides is compensated by the thicker SC, consisting of larger corneocytes covering the aged skin surface due to the retardation of the desquamating process which reduces the water-binding capacity of skin leading to drier skin and more wrinkles. Also oil secreation from sebaceous glands decreases with age leaving skin more dry. Dehydrated and dry skin is more prone to premature aging due to the lack of ceramides.