The structure and function of the skin
Skin is one of the 10 clearly identifiable systems of the human body ( the integumentary system) and its the largest organ, covering up to 3000 square inches.
Its primary function is to protect the body from injury, infection and other damage, while regulating body temperature and detecting outside forces such as touch or pain.
The structure of the skin
There are two layers to skin: the epidermis and the dermis.
'Epi' means higher or upon. In this case the Epidermis is the outer layer of the skin, which includes five layers but is actually the thinner layer:
- Basal or germinal layer – the deepest layer, containing melanocytes, which absorb UV radiation by producing melanin and changing the colour of your skin
- Prickle cell - called this because of how they look
- Granular – containing granules of keratohyalin that help bind keratin together
- Clear – only found covering some parts of the body that need thicker skin, such as the soles of the feet
- Horny – top layer of skin with dying cells filling with keratin protein and waterproofing the skin’s surface before sloughing off and being replaced
The epidermis is also characterised by an absence of blood or lymphatic vessels.
The inner layer of the skin has three thick and tough divisions, largely formed of elastin and collagen fibres. This is the thicker and deeper part of the skin.
The dermis comprises:
- Blood vessels supplying the skin’s glands, muscles and other structures
- Insulating and energy providing subcutaneous fat cells
- Hair follicles that puncture the skin and offer insulation and protection
- Sebaceous glands, which produce sebum to moisturise and protect the skin
- Lymphatic vessels that assist in the movement of lymph around the body
- Sensory nerve endings, which allow us to recognise warmth and cold, touch, pain and pressure
- Sweat glands, comprising eccrine glands rising from the dermis to the skin surface, and apocrine glands, which secrete a thicker and stickier discharge from areas such as the armpits and genitals
'Sub' means under. In this case the sub-dermis is the bottom layer of the skin. It is primarily a fine layer of subcutaneous tissue (fat) under the epidermis / dermis that provides insulation, protection and energy.
The function of the skin
It’s easy to take for granted the protection provided by the skin, which includes the following:
- Temperature regulation through sweating and the vasodilation or vasoconstriction of superficial vessels, depending on whether we need to keep warm or cool down
- Protection from harmful effects of the sun and UV radiation, through the production of vitamin D and melanin
- Shielding the body from injury and infection
- Lubrication and protection from the secretion of sebum
As the largest and the outermost organ of the body, the skin also provides mechanical support for the body, prevents the loss of body fluids and is able to detect changes in temperature, pressure, touch and pain.
The protection provided by the skin can vary depending on age, with babies and children more at risk. Hydrated skin provides less protection than dry skin, and damaged skin is also more vulnerable to penetration by outside substances.
Anyone studying for a Level 3 Diploma in Sports Massage (soft tissue therapy) will learn about the structure and function of skin as part of the anatomy and physiology elements of the course, as well as the principles of soft tissue dysfunction.