The skin is the largest organ of the body and is made up of multiple layers of cells that are constantly going through self shedding and regeneration once every 30 days. The skin is made up of 3 main layers: Epidermis, Dermis and Subcutaneous or hypodermis. These layers are held together by the protein, collagen and elastin fibres. Collagen provides durability and strength. Time taken for deepest layer to come to the top is 45-75 days.
- Top layer – Epidermis
It is made up of 5 layers: Stratum Corneum – horny layer, Stratum lucidum – clear layer, Stratum granulosum – granular layer, Stratum spinosum – spiny layer – prickle cell, melanin production, and Stratum Germinativum – basal Layer- where the cells divide and grow upwards.
Each of these layers has their own layers. The Stratum spinosum gives skin its color.
- Middle layer – Dermis
It is made up of: Blood vessels (supply nutrients to the skin), Lymph vessels (defence mechanism for the immune system), Hair follicles (protection and sebum production), Sweat glands (regulators of heat), and Pain and touch receptors (carry impulses to the brain).
- Bottom layer – Subcutaneous or hypodermis
These are fat cells that conserve body heat while protecting other organs from injury. They provide a cushioning effect and are a source of energy in lean times.
Thickness of layer varies – the thinnest layer is on our eyelids making them light and flexible, the thickest is on our hands and feet for gripping.
Functions of Skin
This skin provides a protective layer for organs and tissues from pathogens, heat and light. It regulates body temperature. It stores water, fat and Vitamin D and has touch receptors that sense pain or pleasure. Skin is an excretory and absorption organ.
Skin has a natural moisturising factor (NMF). Teen skin is prone to oiliness as hormones are regulating. At 20-30 years skin cell turnover provides optimum condition. At 30-40 years cell turnover starts to decrease and fine lines start to appear. At 40-50 years skin becomes more dry. Over 50 years of age, cell turnover drops by 50% resulting in flaky patches and deeper lines.
The skin may be sensitive. Sensitive skin reddens easily due to environmental changes or cosmetic products. Skin can become permanently sensitive due to allergy, shaving, and use of skin care productscontaining alpha hydroxy and retinoic acid skin.