Chronological Occurrences of Wrinkles
The skin is made up of 3 layers: the epidermis, dermis and subcutaneous tissue.
- The epidermis is the outer layer and functions as a barrier to the external environment.
The cells of the epidermis, named keratinocytes, are constantly moving from the bottom to the top layer, and then flake off. If this process becomes abnormal, the skin can look scaly.
- The dermis is the second layer, and contains the structural elements of the skin: the connective tissue. It is constituted by various elements: collagen, giving the skin its strength; glycosaminoglycans bringing to the skin its turgor, and elastin fibers giving the skin its elasticity.
Between epidermis and dermis is laying the dermal-epidermal junction (DEJ), interlocking forming fingerlike projections called rete ridges. Epidermal cells are fed from the blood vessels in the dermis, and the rete ridges increase the surface area of the epidermis in contact with the blood vessels.
- The subcutaneous tissue is the bottom layer of the skin, containing fat cells which make the skin plump and full.
When aging, the epidermal cells become thinner and less sticky, making the skin look thinner, and decreasing the effectiveness of the barrier function, increasing water loss and thus reducing skin hydration, causing dryness.
There are also significant effects of aging on dermis. The production of collagen is decreased, and collagen fibers gather in bundles, losing their effectiveness. Elastin fibers also wear out. Taken together, these changes cause the skin to wrinkle and sag.
The rete ridges of the dermal-epidermal junction flatten out, inhibiting the correct process of bringing nutriments to the epidermis.
In the subcutaneous tissue, fat cells get smaller, leading to more noticeable wrinkles and sagging.