The skin is the largest organ in the body, comprising about 15% of body weight. The total skin surface of an adult ranges from 12-20 square feet. In terms of chemical breakdown, the skin is about 70% water, 25% protein and 2% lipids.
3 Main Layers of The Skin
The skin consists of three main layers – Epidermis, Dermis and Subcutaneous Layer
The epidermis is the topmost layer of the skin. The epidermis has no blood supply, but it’s nourished by the blood vessels in the dermis. The thickness of the epidermis is usually 0.5-1mm but is dependent upon the site (for example, it’s very thick on the soles of feet and palms of hands).
Keratinocytes, the cells that make the protein keratin are the predominant type of cells in the epidermis (makes the skin waterproof & tough). At the lowermost layer of the epidermis are immature, rapidly dividing keratinocytes. As they mature, keratinocytes lose water, flatten out and move upwards, eventually at the end of their life cycle, they reach the uppermost layer of the epidermis called stratum corneum. Stratum corneum consists mainly of dead keratinocytes, hardened protein (keratins) & lipids, forming a protective crust.
Dead cells from stratum corneum continuously slough off and are replaced by new ones coming from below. The skin completely renews itself every 3-5 weeks.
Another significant group of cells in the epidermis are melanocytes, the cells producing melanin, the pigment responsible for skin tone and colour. This darkens the skin and protects you from strong sunlight. The darker the skin the more melanin you have.
Langerhans cells are essentially a fore post of the immune system in the epidermis. They prevent unwanted foreign substances from penetrating the skin. The condition of the epidermis determines how fresh your skin looks and how well your skin absorbs and holds moisture. Wrinkles, however, are formed in lower layers.
The dermis is the middle layer of the skin. It’s the thickest of the skin layers and comprises of a tight, sturdy mesh of collagen & elastic fibres. Both of them are important proteins, as collagen is responsible for structural support and elastin for the resilience of the skin.
The key type of cells in the dermis is fibroblasts, which make collagen, elastin and other structural molecules. The proper function of fibroblasts is highly important for overall skin health.
The dermis also contains capillaries (tiny blood vessels) and lymph nodes (depots of immune cells) the blood vessels carry oxygen and nutrients and lymph nodes for protecting it from micro-organisms. It’s responsible for the skin’s flexibility and mechanical resistance and is also involved in the regulation of the body temperature. The dermis supplies the avascular epidermis with nutrients by means of its vascular network. It contains sense organs for touch, pressure, pain and temperature.
The dermis also contains sebaceous glands, sweat glands, hair follicles and also nerve and muscle cells.
Sebaceous glands, located around hair follicles, are of particular importance for skin health as they produce sebum, an oily protective substance that lubricates and waterproofs the skin and hair. When sebaceous gland produce too little sebum, as is common in older people, the skin becomes excessively dry and more prone to wrinkling. Conversely, over production or improper composition of sebum, as is common in adolescents, often leads to acne.
The dermis is the layer responsible for the skin’s structural integrity, elasticity and resilience. Wrinkles arise and develop in the dermis. The sweat gland is a long, coiled, hollow tube of cells. The coiled part in the dermis is where sweat is produced, and the long portion is a duct that connects the gland to the opening or pore on the skin’s outer surface and some also open into hair follicles.
The Subcutaneous layer
Subcutaneous tissue is the innermost layer of the skin located under the dermis consisting of connective tissue and fat molecules. Subcutaneous fat acts as a shock absorber and heat insulator protecting underlying tissues from cold and mechanical trauma.
The loss of subcutaneous tissue, often occurring with age, leads to facial sagging and wrinkles.
Functions of The Skin:
- Protects the body against physical injury.
- Provides some protection for the body against numerous pathogenic microbes and chemical agents.
- Helps to restrict fluid and water loss.
- Helps to prevent excessive water absorption by imparting water resistance to the skin.
- Is involved in temperature regulation of the body.
- Is the body’s main sensory organ for temperature, pressure, touch and pain.
- Provides protection from UV light.
- Plays a key role in metabolism, including vitamin D synthesis and biotransformation of some chemicals.
- Lack of vitamin D can lead to soft bones and many associated problems.
Any permanent makeup artist has to understand what happens in all the skin layers after pigment has been placed
It is vital to learn about skin layers to prevent excessive pigment fading. The key factor for pigment stability turns out to be the depth of placement. The epidermis cannot retain tattoo pigment since the epidermal cells are prone to migration. As they move towards the surface the residual pigment that they contain will naturally exfoliate with the outer layer of the dead cells. Eventually all epidermal layers will get rid of pigment particles in about 2-3 months, but the speed of pigment turnout will vary in each individual.
The best results are achieved when pigment is placed in the upper third of the dermis. If the needle or blade is injected deeper, the pigment will appear bluish/greenish. The only difficulty is presented by the application technique. It is problematic for the beginner artist to control the depth of pigment placement manually, by the feel of skin’s resistance. skin thickness of epidermis varies in different parts of the body and even alongside the brow. Thus, compared to other parts, eyelids have one of the thinnest epidermises, next come eyebrows and temples.
Pigment injection induces a strong defensive reaction in the body. Some soluble components of the pigment can be quickly absorbed and eliminated by the lymphatic system. This is why brows are a two possibly three-part treatment for a finished result. The skin will naturally try to protect itself and push out the pigment as it is a foreign substance.
- lymphatic system – network of tissues and organs that help rid the body of toxins, waste and other unwanted materials