The Skin Structure and Functions
The skin is the largest organ of the body and it is made up of three layers:
Epidermis – the outer surface of the skin composed of epithelial tissue.
Dermis – provides support for the epidermis and composed of dense connective tissue.
Subcutaneous layer – lies under the skin, rather than being part of it and is composed of areolar connective tissue and adipose tissue.
To completely understand skincare and what is right for you, I thought it would be useful to break down these layers so that you understand what each layer is, its function and what you will find in each layer.
The epidermis is the outer layer of the skin. Its main job is to protect the skin from day to day issues. It consists of five layers:
1. Stratum Corneum
2. Stratum Lucidum
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Germinativum
Stratum Corneum: this is what you can see when you look in a mirror and what you can feel. This is made up of 25-30 rows of flat, dead keratinized cells. These cells usually shed naturally after 14 days. This is where you will also find the natural moisturizing factor (NMF) which moisturizes the skin and waterproofs the skin.
The skins natural moisturizing factor which contains water-soluble substances is made up of:
Mineral salts and other minerals.
Stratum Lucidum and the Stratum Granulosum: this is where the final stages of keratinization take place. The cells become flatter and harder and act as a barrier.
Stratum Spinosum: this layer sits above the germinativum layer. This is where the cells become flatter and less regular in shape. Formed from two to six rows of cells, these cells receive nourishment from the tissue fluid. Each cell has a living nucleus. Towards the upper part of the layer is where keratinization takes place. This is when the cell changes from living cell containing a nucleus, into layers of flat, hard durable cells of protein called keratin. This layer is very important as it is our production and also makes the skin waterproof. Langerhan cells are also present here, they are part of the immune system and act as a defense.
Keratin can be soft or hard depending on its location.
- Hard Keratin – nails
- Soft Keratin – Stratum corneum
- Soft Keratin – Hair
Stratum Germinativum: this is the living layer, each cell has a large, living nucleus. These cells are constantly dividing and producing new cells, a process called mitosis. When a new cell forms, the older cells are pushed upwards through the epidermal layers. You will also find the Merkel cell present here, these sensory cells give us the sense of touch.
Skin usually takes up to 28 days for a cell to move from the germinativum to the corneum.
The cell receives nutrient fluid from blood vessels in the papillary layer of the dermis.
In this layer is where you will find melanocytes, they are large branched cells which produce the pigment melanin.
Melanin is produced by a chemical reaction between tyrosine (an amino acid) and ultraviolet light. Melanin is the skin’s natural protection against harmful U.V light.
The dermis supports and provides nourishment for the epidermis, it sits below the epidermis.
It is divided into two separate layers:
- Papillary layer – upper layer
- Reticular layer – lies below the papillary layer
In these layers is where our nerve endings are – touch and pain nerve endings. It also provides the skin with its structure, collagen, fibers and elasticity. There are also fine capillaries which bring oxygen and nourishment to the skin, fine veins and arteries and lymph vessels. Lymph remove waste and excess tissue fluid and transport lymphocytes which help fight infection.
Structures found in the dermis:
- Collagen fibers
- Elastin fibers
- Blood vessels
- Lymphatic vessels
- Nerve endings
- Hair follicles
Elastin is yellow elastic tissue - a protein which allows the skin to stretch and return to normal.
Collagen is a white fibrous tissue – a protein which gives strength and tension.
The dermis has the highest water content over any part of the skin.
The Subcutaneous layer or hypodermis
The lower layer found under the dermis composed of fat cells and fine fibers. This is where fat is stored, and the muscle tissue lies under this layer. It is a combination of adipose tissue – containing fat cells and areolar tissue which contains elastic fibers which gives it flexibility and elasticity.
Subcutaneous tissue, which is also known as the hypodermis, is the innermost layer of skin. It's made up of fat and connective tissues that house larger blood vessels and nerves, and it acts as an insulator to help regulate body temperature.
Structure found in this layer:
- Fat cells and fine fibers
- Arteries and veins
- Sweat glands
- Nerve endings
This layer protects the underlying organs and it also keeps the body warm as fat is a poor conductor of heat.
Lucy, CIBTAC accredited beauty therapist.
About Lucy Bee Limited
Any information provided by us is not intended to diagnose, treat, cure or prevent disease. We always recommend referring your health queries to a qualified medical practitioner. Members of the Lucy Bee team can only offer their best advice.
Lucy Bee is a lifestyle brand selling skincare and soap products all completely free from palm oil and with minimal use of plastic. Lucy Bee is concerned with Fair Trade, organic, ethical and sustainable living, recycling and empowering people to make informed choices and select quality, natural products for their skin.
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