Intrinsic and extrinsic aging

Intrinsic aging and Extrinsic aging are terms used to describe cutaneous aging of the skin and other parts of the integumentary system, which while having epidermal concomitants, seems to primarily involve the dermis. Intrinsic aging is influenced by internal physiological factors alone, and extrinsic aging by many external factors. Intrinsic aging is also called chronologic aging, and extrinsic aging is most often referred to as photoaging.

Causes and Effects
The effects of intrinsic aging are caused primarily by internal factors alone. It is sometimes referred to as chronological aging and is an inherent degenerative process due to declining physiologic functions and capacities. Such an aging process may include qualitative and quantitative changes and includes diminished or defective synthesis of collagen and elastin in the dermis.

Extrinsic aging of skin is a distinctive declination process caused by external factors which include ultra-violet radiation, cigarette smoking, air pollution, among others. Of all extrinsic causes, radiation from sunlight has the most widespread documentation of its negative effects on the skin. Because of this, extrinsic aging is often referred to as photoaging. Photoaging may be defined as skin changes caused by chronic exposure to UV light. Photodamage, implies changes beyond those associated with aging alone, defined as cutaneous damage caused by chronic exposure to solar radiation and is associated with emergence of neoplastic lesions.