Download How The Skin Works

How The Skin Works
For skin therapists, the skin is the most important organ in the body. The
study of the skin is essential in making a correct diagnosis, thus enabling the
appropriate treatment to be given. Next to the brain, the skin is the most
complex organ of the body.
The skin has 6 functions in the body:
1.Sensation
Because the skin contains so many tactile nerve endings, the brain can
be made aware of the stimuli of pain, heat, and cold in any part of the
body.
2.Heat Regulation
Controls our body temperature so that it maintains our internal heat
regardless of environmental climate. It does this through the excretion
of sweat from the sudoriferous glands, and the dilation of the blood
vessels in the dermis.
3.Absorption
The skin is able to absorb some oil or fat-based substances on a topical
level, but deeper penetration is confined to either medication or
application of a water-based substance by means of galvanic current.
Penetration of cosmetic preparations is restricted to the epidermal
layers only.
4.Protection
Through the fat cells in the subcutaneous tissue, the skin protects the
body against blows and falls. The Stratum Corneum acts as a barrier
against bacterial invasion. The Stratum Germinativum produces melanin
pigment as a natural protection from ultraviolet light.
5.Excretion
The eccrine and apocrine glands excrete perspiration and sweat for
temperature regulation.
6.Secretion
Sebum is secreted by the sebaceous glands and is a complex mixture of lipids and fatty acids.
Adult sebum is fungicidal, germicidal and
inhibits the growth of skin surface bacteria. Sebum plays an important
part in maintaining the surface of the skin intact.
1. The Epidermis consists of keratinized surface layers.
2. The Dermis is made up primarily of collagen (80%) & elastin (3%) (connective tissue)
with sebaceous glands, apocrine glands, eccrine glands and hair follicles; ground
substance, nerves, blood supply -living layer because anything that penetrates the dermis
is absorbed into the blood and lymph supply.
3. The Hypodermis or Subcutaneous Tissue is made up of loose connective tissue
mostly adipose (fat) & blood vessels.
The Epidermis:
Stratum Basal or Germinativum: Produces keratinocyte and melanocyte cells.
Keratinocytes transport cholesterol to the stratum corneum to form a part of the Natural
Moisturizing Factor. 1 in 10 cells is a melanocyte. Skin renews at the rate of 1 million
cells per minute in youth. This is the layer involved in basal cell carcinoma.
Stratum Spinosum: These are cells with 'tonofibrils' extending from the membrane,
hence the layer is referred to as the 'filamentosum.‟ This is the first epidermal layer
involved in allergic response, blistering and squamous cell carcinoma.
Stratum Granulosum: Cells contain granules of 'keratohyalin,‟ which hardens to form
keratin protein. Nuclei is broken down by lamellar bodies within the cell, which then
breaks down to form lipids. Lipids pass through the membrane along with the lamellar
bodies, to form the Natural Moisturizing Factor.
Stratum Lucidum: Translucent and flat cells which are present only in the palms and
soles. Cells are filled with densely packed filaments called 'eleidin' (the horny pads).
Stratum Corneum: Cells are almost devoid of water (6%-9%). Made up of hard
'corneocytes.‟ Lamellar bodies' function to regulate the Natural Moisturizing Factor and
cell thickness, thus regulating absorption in the epidermis.
Stratum Disjunctum: The outer few 'shell' layers of dead epidermal cells. This is the
layer we exfoliate. The journey from the Stratum Germinativum to the Stratum
Corneum during puberty takes between 12-19 days, mid-life 28-35 days, and
up to 90 days at maturity.
Acidic Environment: The pH of the environment is controlled in part by the acid mantle
which is now referred to as the hydrolipid film. The hydrolipid film has a pH of 4.0-6.0
(in healthy people)and supports the formation and maturation of epidermal
lipids; it is often said that it helps maintain the barrier function of the skin. It
also provides indirect protection against invasion by microorganisms and
provides direct protection against alkaline substances with its alkali
neutralizing capacity. If the hydrolipid film becomes disrupted, damaged, or
loses its acidity, the skin is more prone to damage and infection. In
essence, the pH gradient in the Stratum Corneum has a multitude of
benefits that help maintain the epidermis in optimal condition.
The Dermis:
The dermal layer of the skin has been called the "action" layer and is regarded as the
"true" skin. The dermis is made up of connective tissue proteins namely collagen and
elastin, which lend support to the epidermis and give the skin both its moisture retaining
properties and its elastic quality. It is in this layer that the skin’s major aging processes
take place. Being a condensed connective tissue, the dermis is unstable and undergoes
changes, breakdown and renewal. The dermis also contains blood vessels, lymphatics,
nerves, tactile corpuscles, sebaceous glands, sudoriferous glands, and hair follicles. The
dermis has a superficial papillary layer, and a deep reticular layer. For growth, the skin
requires amino acids, vitamins, trace elements, and essential fatty acids. Mitosis (cell
renewal) in the Stratum Germinativum gets the necessary energy from the nutrition
supplied by the blood supply in the dermis. Action in the dermis will ultimately affect the
appearance of the epidermis either obviously, as in a blush due to capillary dilation, or
progressively, such as over or under activity of the primary glands.
The sudoriferous or sweat glands, secrete a weak salt solution that varies in amount
according to our activity and body temperature. They consist of a coiled base and a
tube-like duct which opens on the surface of the skin, forming a pore. There are two
types of sudoriferous glands; apocrine glands, connected with hair follicles and
stimulated by emotions, and eccrine glands, situated all over the body and stimulated by
heat.
The sebaceous glands are sac-like glands attached to hair follicles. These glands are 2-3
times more numerous around vellus hairs (facial area, upper chest and back). The
sebaceous glands manufacture sebum and it travels upward through the hair follicles to
the surface of the skin opening in an ostea (not a pore). Sebum, which is a complex
secretion with a high percentage of fatty acids and lipids, then mixes with the perspiration
from the eccrine glands and forms the skin‟s "acid mantle.” It is this layer of oil and
water, together with the N.M.F., that keeps the epidermis smooth and prevents bacterial
invasion.
The Subcutaneous Tissue:
The subcutaneous tissue is a deeper layer of connective tissue and separates the dermis
from the underlying muscle. An ample supply of blood and lymph vessels, nerve endings,
and fat cells are found here. The fat cells act as a storage depot and helps reduce heat
loss, and also as a shock absorber to protect the bones and internal organs. The adipose
fat cells contain carotene, a yellowish pigment, which lends a "buttery" look to the human
fat cell. It is in the adipose fatty tissue of the subcutaneous layer that we also find the
toxic stubborn cellulite tissue.