Intrinsic ageing and extrinsic ageing are terms used to describe
cutaneous
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different d ...
ageing of the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other animal coverings, such as the arthropod exoskeleton, have different de ...
and other parts of the
integumentary system, which while having
epidermal
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...
concomitants, seems to primarily involve the
dermis. Intrinsic ageing is influenced by internal physiological factors alone, and extrinsic ageing by many external factors. Intrinsic ageing is also called ''chronologic ageing'', and extrinsic ageing is most often referred to as ''photoageing''.
Causes and effects
The effects of ''intrinsic ageing'' are caused primarily by internal factors alone. It is sometimes referred to as chronological ageing and is an inherent degenerative process due to declining physiologic functions and capacities. Such an ageing process may include qualitative and quantitative changes and includes diminished or defective synthesis of
collagen and
elastin in the dermis.
''Extrinsic ageing'' 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 ageing is often referred to as photoageing.
[Uitto J, Fazio MJ, Olsen DR: Cutaneous aging: Molecular alterations in elastic fibers. ''J Cuta Aging & Cos Derm'' 1(1):13-26, 1998.] Photoageing may be defined as skin changes caused by chronic exposure to UV light. ''Photodamage'' implies changes beyond those associated with ageing alone, defined as cutaneous damage caused by chronic exposure to solar radiation and is associated with emergence of neoplastic lesions.
References
Physiology
Senescence