This post is the ultimate guide on the skin so that you can become an expert now.
“Healthy skin isn’t a quick fix”, says Susan West Kurz, a holistic skin care expert and president of Dr. Hauschka Skin.
The skin is unpredictable and you should know where you are to achieve where you'd like to be skin wise.
If you want to become an expert on the skin then keep reading!
The skin is the largest external organ and most important one because it provides a barrier between your body and the outside world.
Functions of The Skin
The skin has a lot of different functions, among the most important are:
- Protects you from the outside world.
- Helps you keep a constant body temperature.
- Absorbs the suns energy and converts it into vitamins.
- Stores fat and water.
- Gets rid of waste.
- Sends sensations.
Structure of The Skin
Having an understanding about the structure of the skin and how it works is an important step to mastering skin care.
All the layers of the skin work in harmony and anything that throws its functions off balance affects all skin layers at the same time.
The skin is a very complex organ made up of three layers:
It's the outermost part of the skin, this layer provides protection to the body and to do its job of defence, it has four main cell types each with a role to play.
- Keratinocytes: these are the main cells in the epidermis, responsable of producing and storing the protein keratin which provides the skin, hair and nails with physical protection and waterproofing.
- Melanocytes: these cells produce the pigment known as melanin, which gives our skin its colour and protects us against UV lights from the sun that damage skin cells DNA.
- Langerhans Cells: these cells are part of the immune system, they work to detect and destroy substances and infections that may invade the skin.
- Merkel Cells: these cells are found deep in the epidermis, they are sensorial which means they provide us with the sensation of touch.
The Epidermis is made up of multiple layers of flattened cells, which are:
Basal/Germinal Layer (Stratum Basale/Germinativum): this layer sits on the bottom of the epidermis and on top of the dermis.
The cells in the basal layer bond to the dermis by collagen fibers known as basement membrane.
The dermal papilla, a finger-like projection, strengthes the connection between the epidermis and dermis.
The stratum basale or germinativum is made up of basal cells, which are cuboidal-shaped stem cells where keratinocytes originate.
The keratinocytes produced from this layer are constantly going through mitosis to produce new cells.
When new cells are formed, the cells that already exist are pushed from the stratum basale and into the stratum spinosum.
There are two other types of cells found among the basal cells. The first, the merkel cell which is very abundant on the surface of the hands as well as the feet. The second, the melanocyte which produces the pigment melanin.
Spinous Layer (Stratum Spinosum): its appearance is spiny thanks to the protruding cell processes that join the cells via a structure called a desmosome.
The bond between the cells strengthens because the desmosomes interlock with each other.
This layer consists of 8 to 10 layers of keratinocytes, formed as a results of cellular division within the stratum germinativum.
Interspersed among the keratinocytes are dendritic cell called the Langerhans cell, incharge of engulfing bacteria, foreign particles, and damaged cells that occur in this layer.
The keratinocytes within the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid that helps prevent water loss from the body, making the skin relatively waterproof. Keratinocytes are then pushed into the stratum granulosum.
Granular Layer (Stratum Granulosum): has a grainy appearance due to the changes that happen to the keratinocytes while they are pushed from this layer.
The cells become flatter, their membrane thickens and generate huge amounts of keratin and keratohyalin, which accumulates within the cells as lamellar granules.
These proteins make up the bulk of the keratinocyte mass in the stratum granulosum.
As the cells die, the nuclei and other cell organelles disintegrate and leave behind keratin, keratohyalin and cell membranes that will form the stratum lucidum, the stratum corneum and the accessory structures of hair and nails.
Clear/Translucent Layer (Stratum Lucidum): this layer is only found in the palms of the hands and soles of the feet. The keratinocytes in this layer are dead and flattened and provide a barrier to water.
Cornified Layer (Stratum Corneum): this layer sits on top, it's entirely replaced during a 4 week period, cells are shed periodically and replaced by cells from the startum granulosum; read more about how the life cycle of the skin cells work.
The stratum corneum is waterproof and prevents bacteria, viruses and other foreign substances to enter into the body.
It's the layer following the epidermis, it's where blood and lymph vessels, nerves, hair follicles and sweat glands are found. It's divided into two layers of connective tissue:
- The upper "papillary" dermis: it's made of areolar connective tissue, meaning the collagen and elastin fibers form a loose mesh. The papillary layer contains:
- Adipocytes (fat cells)
- Small blood vessels
- Phagocytes, cells that fight bacteria and infections.
- Lymphatic capillaries
- Nerve fibers
- Touch receptors called the Meissner corpuscles.
- The lower "reticular" dermis: it's made of irregular connective tissue and it provides the skin with structural support. It's rich in:
- Collagen: it's one of the most abundant proteins found in the body and there are at least 16 different types of collagen in the skin. It provides structure, strength, rigidity and support to the skin and it keeps skin hydrated by binding water.
- Hyaluronic Acid: It's a large sugar molecule with a gel-like consistency, it keeps the skin hydrated, soft and plump.
- Elastin: is a connective tissue protein which gives skin elasticity, meaning that even after it has been stretched, pinched or poked it can take its original shape.
Also known as the subcutaneous layer or superficial fascia, it's the layer following the dermis and it consists of adipose tissue, made of fat-storing cells called adipocytes.
This stored fat serves as an energy reserve, insulates the body and acts as a cushion to protect underlying structures.
Hormones and genetic factors determine where the fat is deposited and accumulates within the hypodermis.
As our bodies mature and age, fat distribution changes, men tend to accumulate fat in different areas than where women do.
Healthy skin is critical for ones health because it protects against disease and exposure.
Frequently Asked Questions
Yes, the skin is an organ.
The 3 layers of the skin are: