The document summarizes the different layers of the epidermis: The stratum corneum is the outermost layer and contains fatty material that keeps the skin waterproof and prevents cracking. The stratum lucidum is only a few cells deep and may control water transmission. The stratum granulosum contains flat, keratinizing cells and represents the first stage of transformation into horny material. The deeper layers of the epidermis contain dividing cells that push older cells upwards. The epidermis generates new cells and provides defense against infection through its layers, oils and immune cells.

2. Stratum Corneum
 The cells contain an epidermal fatty material which
keeps them waterproof and helps the skin from
cracking and becoming open to infection.
 This layer is the outer layer of the skin and forms the
thickest part of the epidermis in many parts of the
body.

3. Stratum Lucidum
 This layer derives its name from its clear/translucent,
almost transparent appearance. Only a few cells deep
in the stratum lucidum lie between the outer horny
layer and the inner granular layer.
 It is thought that this layer is the site of the barrier
zone controlling the transmission of water through the
skin.

4. Stratum Granulosum
 The thickness of this layer may vary from one to
several cells deep and is thickest on the palms of the
hands and the soles of the feet.
 The cells are flat and becoming keratinised. These
cells reflect light and give the skin a white appearance.
 Keratinisation is the change of living cells into dead
horny flat cells. Loss of fluid is an essential process in
the stages of keratinisation and the stratum
granulosum cells are believed to represent the first
stage in the transformation of the epidermal cells into
the horny keratin material.

5. Stratum Spinosum
 The prickle cell layer is often classed with the stratum
germinativum to form the malpighian layer.
 The Malpighian layer of the skin is a term that is
generally defined as both the stratum basil and
stratum spinosum as a unit

6. Stratum Germinativum or Basil
layer
 This is the deepest section of the epidermis and is in
contact with the dermis from which it derives its nutrient
fluids via the capillary blood vessels. The process of cell
division known as mitosis takes place in this basal layer as
the development of new cells leads to a gradual
displacement of the older cells towards the surface.
 The epidermis is a reproductively self-sufficient system.
For example, it generates entirely from the cells resident
within it. The basal layer is at its most productive between
midnight and four am. This could explain the term 'beauty
sleep'.

7. Preventing Infection
 The natural layer of oil-in-water emulsion on the skin
is the first barrier against invasion by micro-organisms
such as bacteria, fungi and yeasts. The stratum
corneum provides the next level of defence.
 The epidermis also contains special defence cells
(Langerhans cells) which are spread out amongst the
keratinocytes. These cells mop up invading substances
found in the body and take them to special white
blood cells called lymphocytes, which are found in
lymph glands. Here they are then neutralised.

8. Preventing Infection
 An important element of defence concerns chemicals.
If a chemical such as nickel is constantly absorbed
through the skin, say from a button on one's jeans, it is
first taken up by the Langerhans cells. However later
special lymphocytes called T-cells make antibodies to
that chemical. This can in time lead to an allergic skin
reaction at the site of the button as the T-cells rush to
meet the invading chemical.