3.1 Anatomy of the skin 101

Did you know that the skin is actually the largest organ of the body? In fact, our skin equates to about 16% of our total body weight! It can be a bit weird to think about our skin as an organ, because usually when we think of organs, we usually think of our internal organs such as lungs, heart, and brain. Our skin has a really important role to play as it serves as a protective, waterproof layer to protect our internal organs and also helps us to regulate temperatures, permits sensations (like touch, heat and cold) and helps with our immune defence. Given your role as an MUA is to work with so many different skin types, having a solid understanding of all things skin-related is a must!

In this lesson, we will start by looking at the anatomy of the skin. Anatomy is the study of the structure or internal workings of something, so essentially it is focussed on how stuff works! Once you have a general understanding of the skin, you will then learn more about the face, the eyes, the brows, the mouth in the next lesson. Unfortunately, a lot of training out there skips past anatomical considerations, which means there are many MUAs that don’t really understand how and why things work. We have included this in our training because the ‘how and why’ is so important when it comes to selecting the most appropriate products and application techniques for your clients. In addition to this, knowing the scientific names for the anatomy is not essential, but it furthers your learning, and it’s good to use the correct terminology!

The layers of the skin

The skin across different parts of our body changes; some surfaces can have thin layers, thick layers and another part can be hairy. Regardless of which part of the body, our skin is divided into three layers called the epidermis, the dermis and the subcutis. The table below outlines each layer in more detail:

Skin layerOverviewMain roles
EpidermisThe epidermis is the outermost layer of skin and provides a waterproof barrier. The epidermis is subdivided into five layers:
1. Stratum corneum
2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum germinativum (basal layer)
Makes new skin cells
Creates our skin tone
Protects the body
DermisThe dermis is the second layer and is beneath the epidermis. The dermis contains tough connective tissue, hair follicles, and sweat glands. The dermis is further split into two layers:
1. Papillary region
2. Reticular region
Makes sweat and oil
Provides sensations and blood to the skin
Grows hair
Subcutis (subcutaneous or hypodermis)The subcutis is a deeper subcutaneous tissue (hypodermis) that is not technically skin as it is made of fat and connective tissue.Attaches dermis to the body
Controls body temperature
Stores fat
Cushions the internal organs against shocks
Separates the skin from underlying muscles

To put this into perspective, the graphic below shows each of the three skin layers on the right, and on the left, you can see the five layers of the epidermis:

As an MUA, you are working predominantly with the client’s epidermis – the outermost layer. For your own understanding, the table below outlines each layer of the epidermis in more detail:

Epidermis layerOverview
1. Stratum corneumThe stratum corneum is also known as the surface/horny layer and is the outermost layer of the epidermis. This layer is made up of many microscopic parts, including the microbiome, the acid mantle, the lipid barrier, and layers of dead skin cells. This layer is made up of 10 to 30 thin layers which continually shed dead skin cells. Complete cell turnover occurs every 28 to 30 days in young adults, while the same process takes 45 to 50 days in elderly adults.
2. Stratum lucidumStratum Lucidum is a translucent layer and lies directly underneath the corneum but not present all the time. This layer is found only on the palms of the hands, fingertips, and the soles of the feet.
3. Stratum granulosumStratum Granulosum is also known as the granular layer and lies underneath the lucidum. Skin cells break down in this layer, and keratin is impregnated into the cells. There is a process known as ‘keratinisation’ whereby cells begin to lose their structure and eventually dies.
4. Stratum spinosumStratum Spinosum is also known as the prickle cell layer or squamous cell layer and lies under the Granulosum. This layer rapidly divides as keratin is pushed into them, making their cells tough and waterproof. This is the thickest layer of the epidermis. This layer gives the skin strength as well as flexibility.
5. Stratum germinativum (basal layer)Stratum Germinativum, also known as the basal layer, is the innermost layer of the epidermis. This is where the skins most important cells, called keratinocytes, are formed before moving up to the surface of the epidermis. This is a living layer that receives its blood supply from the dermis. It produces new cells which reproduce by mitosis (each cell divides into two), which are pushed up through the overlying layers of the epidermis where they eventually lose their nuclei and die, which aids in continually repairing the skin. Melanocytes (pigment-producing cells) are found in this layer, and they are responsible for our skin colour and help protect us from UV.

If you would like to learn more about the layers of the skin and layers of the epidermis, you may like to access the resources linked:

Another important factor that will impact your makeup applications is the pH levels of your client’s skin. Put simply, pH is a measurement figure expressing the acidity or alkalinity of a solution. You may have seen pH scales before:

As you can see on the scale above, a battery is very acidic, and solutions such as bleach are alkaline, with water being neutral. In terms of the pH level of our skin, it is said that the optimal level is between 4.5 and 5.5 for women. All of us have something known as the ‘acid mantle’ layer of the skin, and this essentially describes how acidic our skin is.

Key phrase | Acid Mantle: Your acid mantle is a balanced microflora ecosystem made up of sebum (an oily, waxy substance produced by your body’s sebaceous glands), fatty acids, lactic acid, amino acids and sweat, which keeps out viruses, bacteria, and other harmful microbes. It’s essentially a thin, protective film that covers your skin and also slightly acidic with a pH between 4.5 and 5.5 (which is why it’s called the acid mantle).

Dermatologists suggest that oily skin will usually have a pH range from 4 to 5.2, with dry skin having a pH above 5.5. Now, you won’t be doing any dermatological tests to determine your client’s pH level, but it is important to know what to look out for because you will need to use different products depending on the client’s skin. As a starting point, see you can determine the pH level of your own skin. The table below outlines what you can look out for to determine whether or not your acid mantle is too acidic or too alkaline:

Acid mantle might be too acidic because:Acid mantle might be too alkaline because:
You rarely need to use moisturiser
Your skin is reactive and sensitive to products
Your skin is oily and prone to blackheads, pimples and acne
Your skin often feels irritated or red
Your skin looks greasy
You wake up with an oily face
Your skin feels tight and dry after cleansing
You need to apply moisturiser throughout the day because your skin gets too dry
You sometimes get dry or rough patches or flaky bits on your skin
Your skin looks dull and in the morning shows more lines and wrinkles
Your skin rarely appears plump and dewy

So, if you tend to have oilier skin, your acid mantle may be too acidic, and if your skin is dry or flaky, your skin may be too alkaline. Our pH levels also change continually based on what we eat, how much sleep we get, our stress levels and the environment we live in. Other factors which can impact our skin pH include, but are not limited to:

  • Change in seasons, with different humidity levels and pollution
  • Ingredients in cosmetics, detergents, antibacterial soaps and gels
  • Sebum, skin moisture and sweat
  • Overexposure to the sun
  • Too frequent washing of your skin or skincare routine is too harsh

When trying to determine a clients pH levels on face value, it is useful to think about the four common skin types: normal, oily, dry and combination. The table below outlines each of these in more detail:

Skin typeOverviewWhat to look for
NormalA normal skin type is where the skin is well balanced and healthy. This means that it is neither oily nor dry, and normal skin will usually have balanced sebum and good blood circulation.Fine pores
Good blood circulation
Soft and smooth texture
No blemishes
No sensitivities
OilyAn oily skin type is where there are higher levels of sebum production. Clients with this skin type will likely have a glossy shine to the skin, visible pores and may be prone to acne breakouts.Enlarged and clearly visible pores 
Blackhead and whiteheads
A glossy shineAcne
DryA dry skin type is where there is not enough sebum produced in contrast to the ‘normal’ skin type. Usually, dry skin will lack the lipids needed to retain moisture. This skin type can feel tight, rough, flaky and may look dull.Mild scaling or flakiness in patches 
A rough and blotchy appearance
A feeling of tightness Possible itchiness
CombinationAs the name suggests, a combination skin type is a mix of skin types. If your client has an oily T-zone but dry cheeks, this would indicate a combination skin type.An oily T-zone (forehead, chin and nose) 
Enlarged pores in this area, perhaps with some impurities
Normal to dry cheeks

In addition to the four skin types above, we also need to consider sensitive skin and mature age skin. A client with a sensitive skin type will usually be prone to inflammation and reactions to certain products. Clients with sensitive skin may have strong reactions to chemicals, dyes and fragrances, so you will need to be very careful with the sorts of products you use. As we get older, our skin begins to change, and it will usually become thinner lack hydration, and we will begin to form wrinkles.

The ageing process happens to all of us, and it will usually start from age 35 onwards, although premature aging can occur depending on a person’s overall health, wellbeing, level of sun exposure and genetics. We will learn more about considerations for applying makeup to clients with mature skin later in this module, but for now, key signs of mature age skin include, but are not limited to:


A common sign of ageing is the thinning of the skin. This occurs when the basal cell layer of the epidermis slows its rate of cell production and thins the epidermis. In addition to the skin thinning, our blood vessel walls also thin when we age, so mature clients might also notice that they bruise more easily.


Our sebaceous glands produce less oil as we age, and women experience more of a decrease in comparison to men. Women gradually produce less oil beginning after menopause which can make it challenging to keep the skin hydrated. This can result in dry spots on their skin, often on their lower legs, elbows, and lower arms. Dry skin patches feel rough and scaly.


Wrinkles occur due to reduced elastin and collagen and the thinning of the skin. This means that parts of the face that move frequently (like the eyes, mouth and forehead) are especially prone to lines and wrinkles.

Age spots and skin tags

Age spots are caused by pigment cells (melanocytes) which increase in number and cluster in certain areas. These ‘clusters’ form what is known as age or liver spots. Areas that have been exposed to the sun, such as the backs of the hands, are particularly prone to age spots. Skin tags are small; usually flesh-coloured growths of skin that have a raised surface and are often found on the eyelids, neck, and body folds such as the armpit, chest, and groin. They become common as people age, especially for women.

To put this into perspective, let’s look at the layers of the skin again with the age-related changes happening in the epidermis and dermis. The figure below outlines these changes:

As you can see, aging skin will usually be thinner, dryer, have paler skin and fewer active follicles, meaning sparser eyebrow hairs. With the right techniques and products, as MUAs, we can apply beautiful makeup applications to our mature with no fuss!

If you are interested in learning more about skin types, access the resources linked:

Once you have a better understanding of the type of skin your client, you can then make some assumptions about the pH levels you are working with. If you remember from earlier, clients who have oily skin will usually be more acidic, and clients with dry skin will tend to be more alkaline! In addition to your client’s natural pH levels, you also need to consider the pH levels of your products. Any products with pH values above 7 should be avoided as they can cause undesirable reactions. You will learn more about matching products to skin types and common product ingredients later in this module.

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