Welcome to the hub of skin physiology: a place to learn more about how skin works and how it is structured, so we can take better care of it.
For all the time and money I spend researching new miracle skincare products, I have to have faith that skincare products actually work. But better than faith and hope in skincare matters is science. And to fully understand how products work, you first have to understand a bit more about skin.
So here goes: skin physiology 1-0-1.
The first thing you need to know about skin (and it actually blows my mind away every time) is that it is actually the biggest human organs and its surface covers roughly 2m square. We often think about heart, lungs or intestine as key vital organs; skin hardly ever makes it to the “top-of-mind organ list” (if such list even exists), yet it is the first protective barrier between our bodies and the external world and its breadth of nasty pathogen agents.
Healthy skin is critical to maintaining the integrity of the body. It protects against infections and illnesses, enables our sense of touch and sensations, helps regulate body temperature, takes part in the synthesis of Vitamin D which is in turn key to maintaining a healthy bone structure and to aid cellular communication. My obsession for maintaining a healthy skin does not seem that shallow now, does it ?
Now let’s get technical. Skin is composed of 3 layers – The Epidermis, the Dermis and the Hypodermis (easy): 
- 1) The Epidermis is the thinnest, top layer of the skin (roughly 1mm deep).
- This part of the skin does not have blood-vessel (which comes in handy if you happen to cut yourself with a sheet of paper every so often, at least the epidermis won’t bleed if this stays superficial) and is made up majoritarily of keratinocytes (creating keratin protein, like hair or nails but a softer kind).
- The Epidermis itself is made of different layers of cells – to keep it simpler, lets’ consider 3 sub-layers as low, mid and upper epidermis:
- The lower epidermis, closer to the junction with the Dermis, is made of basal stem cells that divide and multiply to rejuvenate the middle and upper epidermis.
- In the mid-epidermis, you can find 3 other important types of cells like Melanocytes (which are responsible for variations in skin colour and interact with sun light to create a tan), Merkel Cells (providing a sense of light-touch), and Langerhans cells (acting like a detector against external pathogens).
- With time, keratinocytes move up from the lower to middle epidermis as they evolve shape and function, to end up in the upper epidermis, closer to skin surface where they finish their journey and die (these dead cells on the surface of skin are the ones you scrub away (every week, religiously) to reveal newer, more glowing skin underneath).
- The top of the skin is thinly coated by a protective layer of sebum, a natural oil-based liquid which helps defend skin against external aggressions. When sebum production gets ahead of itself, skin pores can become obstructed and prone to blemishes and spots.
- 2) The Dermis which as you guessed sits nicely under the Epidermis, is connected to it by a small membrane.
- The dermis is a thicker layer of skin, made of connective tissues and elastic fibers including collagen, acting a bit like a cushion structure around the body, giving skin its supple appearance.
- It also contains other structures like nerve endings (to provide the sense of touch, cold, heat and pain), hair follicles, sweat and sebaceous glands, and lymphatic and blood vessels.
- 3) The Hypodermis (not technically part of the skin itself), connects the skin to the bones and muscles trough loose connective tissues and elastin.
- It is made of fat, which serves as an other layer of cushion and insulation for the body.
- It contains adipocytes (cells stocking fat as energy reserves for the body and which can cause cellulite appearance when in excess), fibroblasts (cells producing collagen and elastic fibres that are needed in the dermis) and macrophages (soldier cells that attack any nasty pathogens that manage to make it through the skin barrier).
Now you might start to understand that skincare can have different types of effects depending on what level of the skin they target.
Because the hypodermis contains fibroblasts synthesizing collagen and elastic fibres found in the dermis, skincare products with an effect targeting these deeper layers of skin will have a greater, longer-term impact on skin youthful look and suppleness than those with an effect on epidermis only:
- Basic moisturisers containing molecules like glycerin or other basic humectants only act at the surface of the epidermis, a bit like a short-term lubricant coating at the skin surface giving it an instant glow and protection.
- Advanced skincare on the other hand can have a full range of lot more targeted actions at several levels in the skin, whether it is stimulating stem cells, fibroblasts or collagen fibres. However most of the improvement they promise will take longer to materialise, as they will influence skin over time as part of its 28-days renewal cycle, influencing skin’s future appearance.
So it might well be worth paying the extra few pounds on this advanced anti-ageing moisturisers, and also give it a few more days to prove itself (probably 28 if you ask me), before you ditch it in the bin 😉
The skinologist 