1. The skin
A competent therapist needs a good knowledge of the skin in order to
understand treatment effects and recognise disorders.
2. The skin
• Is part of the integumentary system, together with the hair and nails
• Is made up of the epidermis on the outside, and dermis below
• Subcutaneous layer (adipose cells) lies beneath the dermis and is
considered part of the system
• Varies in thickness (1.5-4mm) dependent on the part of the body
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3. The skin
• It is one of the largest organs and covers the whole body
• The epidermis has five layers of epithelial tissue
• The skin weighs about 3.5 kilos
• It has about 640,000 sensory receptors
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4. Epidermis
• Forms the outer portion and is composed of five layers of stratified
squamous epithelium
• In the soles of the feet and palms of the hands the epidermis is
thickest, while in other areas – such as eyelids – the skin is thinner
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5. Layers of the epidermis
From the top down:
• Stratum corneum or horny layer
• Stratum lucidum or clear layer
• Stratum granulosum or granular layer
• Stratum spinosum or prickle cell layer
• Stratum germinativum or basal layer
Stratum means layer, and the second part of the name refers to its
structure or function
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6. Layers of the epidermis
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STRATUM CORNEUM
STRATUM LUCIDUM
STRATUM GRANULOSUM
STRATUM SPINOSUM
STRATUM GERMINATIVUM
7. Stratum corneum
• Most superficial layer
• Consists of hardened, flattened, dead
cells and keratin
• This layer is sloughed off continually as
new cells take its place. The process –
desquamation – slows with age
• Complete cell turnover occurs every 28
to 30 days in young adults, while the
same process takes 45 to 50 days in
elderly adults
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8. Stratum lucidum
• More pronounced in thickened areas of the skin, such as the soles of
the feet and palms of the hands
• A narrow, transparent layer – hence the term clear layer
• Consists of densely packed, flat cells filled with keratin
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9. Stratum granulosum
• Cells have a granular appearance and are flat, and spindle shaped
• As the cells die, they fill with granules of keratin, and keratinisation
(hardening of cells) takes place
• The keratin helps to seal the skin and prevent water loss
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10. Stratum spinosum
• Living cells which are round and filled with fluid
• They have fibrils that interlock, allowing them to attach to other cells
• The main function of this layer is to help prevent bacteria entering
and moisture escaping
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11. Stratum germinativum
The deepest living layer of the epidermis where cell
reproduction – mitosis – takes place.
Receives a rich blood supply from the underlying papillary
layer of the dermis.
Contains cells called melanocytes, which produce the skin
colouring or pigment known as melanin.
Langerhans cells are found in this layer – they absorb and
remove foreign bodies that enter the skin.
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13. Melanocytes
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• Star-shaped cells that produce the skin pigment melanin, to protect it
from the harmful effects of sunlight
• Produced in abundance in dark skins, adding protection, and is totally
absent in albino skins
• UV rays of the sun activate increased production of melanocytes
causing melanin to rise, darkening the skin
• The number of melanocytes is the same for dark and light skins – it is
the melanin synthesis rate that is different
15. Learner activity
• Draw, colour and label a diagram of the epidermis
• Identify how each layer is different, and how the cells change
• State the function for each layer
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