Comprehensive Guide to the layers of your skin

Our skin is the largest organ in the body, and the most visible. Yet, few of us really understand how it works. When searching the internet for causes and treatments of our skin conditions, for example, we often come across terms like ‘epidermis’ and ‘dermis’ that are literally Greek and hard to understand.

As a result, it’s difficult to know exactly how to care for the largest organ in our body. As our outer layer endures harsh external conditions such as environmental pollutants, UV rays, pressure, temperature, and others, how can we best protect and keep it in good health?

To answer this question, let’s start with a skin 101 primer.

Our epidermis

The outermost layer of the skin is known as the epidermis. It consists of four layers of closely packed cells. Cells found in these layers are called keratinocytes. They manufacture and store keratin which is the protein that makes up the main structure of our hair, skin and nails.

From deep to superficial, the four layers in the epidermis are stratum basale (deepest), stratum spinosum, stratum granulosum and stratum corneum (outermost).

In the epidermis of certain body parts with larger thickness, such as palms, soles and digits, there is an additional layer of cells called stratum lucidum. It is found wedged between the stratum corneum and the stratum granulosum.

The dermis

The dermis refers to the inner layer found between the epidermis and subcutaneous (= under the skin) fat. The dermis layers are made of connective tissues, linked by interwoven fibres of collagen and elastin, packed in bundles.

Collagen takes up 70% of the weight of the dermis. Collagen fibers provides the skin with structural support and tensile strength. Collagen proteins also bind to water, keeping the entire organ well hydrated. Accounting for 2% of the weight of the dermis, elastin fibers allow movement and are responsible for elasticity of the layer.

Caring for the skin we see

In the outermost layer, known as the stratum corneum, the keratinocytes are actually dead cells pushed up from deeper layers. As these cells travel to the surface, they undergo keratinization, the process whereby the contents of the cell develop tough keratin proteins. Other components such as cholesterol, ceramides and free fatty acids in the stratum corneum also work together to give a toughness to the skin that can withstand all sorts of chemical and mechanical insults.

In this way, the stratum corneum becomes a barrier that prevents dehydration of underlying tissues and serves as a mechanical protection for the more delicate layers below. It is also the layer most crucial in maintaining moisture.

The stratum corneum layer is usually replaced with cell division and renewal in a cycle of 4 weeks.

Ageing and exposure to ultraviolet radiation can stress the skin, leading to poor barrier function and an increase in water loss. The barrier function can also be affected by other factors such as a deficiency in fatty acids and lipids, detergents (usually from harsh cleansers) or dehydration.

Caring for your skin then should involve a regimen of protecting it from the sun with UV protection, using cleaners and other products that do not dehydrate, and maintaining the moisture in skin through moisturizers. Cleansers, in particular, can contain harsh surfactants that emulsify to remove grease and dirt. These however can irritate the skin. Use a gentle cleanser with a natural emulsifier instead. For example, Dr TWL’s  Miel Honey™ Cleanser uses medical-grade honey as a natural emulsifier, leaving the epidermis both clean and gently moisturized.

Many cosmetic treatments work by causing a change in the epidermal layer, thereby encouraging it to renew itself faster. Procedures targeting the epidermis include some forms of chemical peels, lasers, intense pulse light (IPL), microneedling or topical drugs.

Caring for the skin beneath

The dermis, the layer beneath the epidermis, gets thinner and loses its elasticity over time.

Various cosmetic treatments available often aim to restore the amount of collagen lost during the ageing process, such as medium and deep chemical peels, microneedling, microfocused ultrasound and ablative lasers. Fillers can also restore the volume of collagen in the dermis layer, correcting fine lines and wrinkles.

Lasers, IPL or resurfacing treatments can differ according to the skin layer that it targets – the epidermis or dermis layer. Non-ablative treatments focus on the dermis while leaving the epidermis intact. Ablative lasers treat both dermis and epidermis layers.

Chemical peels can reach different levels depending on the frequency, the peeling substance (typically an acid), the concentration of the substance, and dermal condition of the patient. In a controlled manner, skin cells are destroyed in a chemical peel to stimulate regeneration of a smoother epidermis and new collagen in the dermis.

© 2018 TWL Specialist Skin and Laser Centre. All rights reserved.

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Meet with Dr. Teo Wan Lin, an accredited dermatologist at TWL Specialist Skin & Laser Centre, for a thorough consultation to determine the most suitable treatment for your skin.

To book an appointment with Dr. Teo, call us at +65 6355 0522, or email appt@twlskin.com. Alternatively, you may fill up our contact form here.