Skin Ageing

Intrinsic and extrinsic skin ageing

Skin ages intrinsically (chronologically from within) and extrinsically (due to external factors). Intrinsic skin ageing results from the passage of time and is mainly due to the action of reactive oxygen species (ROS) (Box 1) (Naidoo and Birch-Machin, 2017). It occurs within the skin itself due to reductions in dermal mast cells, fibroblasts and collagen production, and a flattening of the junction between the epidermis and dermis. Intrinsically aged skin is unblemished, smooth, pale, dry and less elastic with fine wrinkles (Landau, 2007).

The fact that it covers the entire body means the skin is the most obvious place to observe signs of ageing. The skin is the body’s largest organ – an average adult’s skin has a surface area of approximately 1.67m² and weighs around 4-5kg (Marieb and Hoehn, 2015). Skin is a malleable but tough structure, serving as a bag holding in all the body’s contents; without it, we would quickly succumb to water and heat loss, and pathogen invasion.

Skin ages intrinsically (chronologically from within) and extrinsically (due to external factors). Intrinsic skin ageing results from the passage of time and is mainly due to the action of reactive oxygen species (ROS) (Box 1) (Naidoo and Birch-Machin, 2017). It occurs within the skin itself due to reductions in dermal mast cells, fibroblasts and collagen production, and a flattening of the junction between the epidermis and dermis. Intrinsically aged skin is unblemished, smooth, pale, dry and less elastic with fine wrinkles (Landau, 2007).

The greatest source of extrinsic ageing is accumulated, unprotected exposure to UV radiation; over 80% of facial skin ageing is due to low-grade chronic UV exposure (Flament et al, 2013). Actinic exposure affects the epidermis, causing irreparable damage to cellular DNA, and induces the generation of ROS. Less than 30 minutes after UV irradiation, the amount of hydrogen peroxide – a potent ROS – has been shown to more than double in human skin (Rigel et al, 2004). UV exposure also disrupts collagen synthesis, leading to acute collagen loss (Rinnerthaler et al, 2015).

Extrinsically aged skin is characterised by coarse and deep wrinkling, rough texture, telangiectasia (spider veins), irregular or mottled pigmentation, a sallow or yellow complexion and a loss of elasticity (Tobin, 2017). The severity of extrinsic ageing depends on skin type – fairer skin is affected more than darker skin.

Wrinkles & Sagging

Several factors contribute to the formation of wrinkles: gravitational force, loss of subcutaneous fat and repeated traction exerted by facial muscles over expression lines, which results in deep creases over the forehead, between the eyebrows, peri-orbitally and in the nasolabial folds. Clinical manifestations include dryness, laxity and slackness; these are most easily observed on the face, which is the most exposed area of skin. In addition, facial muscles show an accumulation of the ‘age pigment’ lipofuscin, a marker of muscle cell damage. This damage, along with diminished neuromuscular control, contributes to wrinkle formation.

Depletion and redistribution of facial fat (which tends to accumulate in pockets such as the nasolabial folds and submandibular region) as well as gravity contribute to the loosening and sagging of the skin.

Changes in hair and nails

Chest, axillary and pubic hair all decrease in density with age, but men may experience increased hair growth in other body sites like the eyebrows, ears and nostrils (Tobin, 2017). Hair becomes drier because sebaceous glands produce less sebum.

Hair greying, which is genetically controlled, appears to be a consequence of a depletion of hair melanocytes, which can no longer provide colour to the developing hair in the follicle. This depletion may occur as a result of signal failing by melanocyte stem cells, which can no longer maintain the production of melanocytes (Nishimura et al, 2005). Wood et al (2009) have shown that hydrogen peroxide, which is produced by hair follicles, builds up over time and leads to a gradual loss of hair colour. Greying occurs at different rates in different hair follicles, either rapidly or slowly over decades. White hair is thicker and grows faster than pigmented hair (Trueb and Tobin, 2010).

Source: www.nursingtimes.net