Q&A Flashcards
What is the skin composed of
Dermis and epidermis
How thick is the dermis
3-5mm
How thick is the epidermis
0.06-0.8mm
What does the dermis contain
Blood vessels, hair follicles , sweat glands
What does the epidermis contain
4 layers of densely packed keratinocytes
Examples of skin functions
Barrier
Protects
Prevents water loss
Regulates body temp
Nerve fibres - sensory
Production of vitamin D
Role of epidermis
Skin barrier function , physical - thermal protection/chemical - keep pollutants out and biological barrier - protect against microbes
What are the layers of the epidermis
The basal cell layer (stratum basale),
The spinous cell layer (stratum spinosum),
The granular cell layer (stratum granulosum),
The stratum corneum (SC)
What 4 cells does the epidermis contain
Keratinocytes
Melanocytes
Langerhans
Merkel cell
What is the structure of cells in basal cell layer
cells are cuboidal to columnar in shape and adhere to the basement membrane via hemidesmosomes, and with their neighbouring
cell with desmosomes
How do cells divide in basal cell layer
Mitosis
How many days til skin completely renews itself
28 days
How do consumers affect desquamation
Mechanical exfoliators or chemical exfoliators
What factors affect desquamation in older skin
Environmental factors - UV light
Hormonal influences - Oestrogens
Deficiencies - vitamin A
What occurs to skin in psoriasis
Increased production of corneocytes
Function of stratum corneum
Prevents water loss and protects the skin from UV light, oxidants, antigens and toxic agents
What is stratum corneum composed of
Corneocytes and intercorneocyte ( intercellular lipids)
What is bricks and mortar model
Stratum corneum is composed of flat cells (bricks) and lipid matrix (mortar)
What is the acid mantle & its pH
The very outermost layers of stratum corneum 4.5-6.5
What is the function of acid mantle
Inhibit growth of harmful bacteria / fungi , acidity helps maintain hardness of keratin proteins
What happens if acid mantle is disrupted
If it becomes alkaline then can lead to infection, dehydration, roughness and irritation
What is the basement membrane
Below the epidermis , specialised structure that lies between dermis and epidermis
Function of basement membrane
Adhesion complex of dermis and epidermis , providing support for the basal cells to allow growth , multiplication and migration allowing nutrients and cells to cross from dermis
What is the dermis
The deep layer that forms bulk of the skin
Function of dermis
Structural integrity, elasticity and resilience
Cells found in dermis
Fibroblasts
Blood vessels
Specialised nerves
What is the skin immune system composed off
Physical barrier
Innate immune system
Adaptive immune system
Physical barrier role as defence
to invaders; the morphological nature of the skin prevents easy access for many
foreign pathogens. Further, secretions from the skin, including sebum and sweat, make the pH of the skin surface between 3 and 5, thus preventing microbial colonization
Innate immune system
represents the body’s initial immune response to pathogen invasion. When tissues are invaded by foreign substances (pathogens), such as bacteria, viruses, fungi, or parasites, the infected cells can communicate their distress through cellular signalling. This leads to mobilization of phagocytic cells, which circulate in the blood stream, and migrate to areas of tissue injury where they seek pathogens and destroy them. Typically, phagocytes are white blood cells (leukocytes), which function by engulfing the pathogen.
Adaptive immun system
in many cases the immune system is not familiar with a pathogen
and therefore relies on a more complex immune slower response called adaptive immunity. The
pathogen antigen first must be processed and recognised by Langerhans cells. After capturing
antigens in the epidermis, Langerhans cells migrate to lymph tissue where they present antigen to
lymphocytes (T cells and B cells).
* T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for
humoral immunity (relating to antibodies).
* B cells respond to pathogens by producing large quantities of antibodies which then neutralise
pathogens
* T cells, called T helper cells, produce cytokines that direct immune response, while other T cells,
called cytotoxic T cells, produce toxic granules that contain powerful enzymes which induce the
death of pathogen infected cells.
What are skin appendages
Hair, nails and sebaceous glands
What is the pilosebaceous unit
Structures consisting of hair , hair follicles, arrector pilli muscle and sebaceous glands
Function of nail unit
Protect the sensitive tips of fingers and tops of toes from injury
Where are sweat glands concentrated
Axilla, forehead , palms and soles
Why do we sweat
When the body needs to loose heat
What do sweat glands respond to
Environmental temperatures, UV light, emotional stress, increase in body temperature
What is sweat
Ultrafiltrate of plasma containing water, inorganic ions - nacl, proteins, latic acid and urea
Hypodermis what is it
Innermost layer of the skin of subcutaneous fat and its thickness varies in different regions of body
What cells are in hypodermis and what is the function
Adipocytes , act as a shock absorber and heat insulator , protecting underlying tissues from cold and mechanical trauma
What does the microbiota include
Bacteria, fungi , mites and viruses
What does the microbiota do
Protect against pathogens, modulate immune systems
What happens if microbiome
Skin conditions such as eczema, dandruff, acne or dermatits
What influences the skin microbiome
pH , sebum content, barrier function, hydration , climate , uv pollution, antibiotics, lifestyle factors - diet/hygiene/alcohol
What bacteria can be found in/on skin
Corynebacteria, Propionibacteria (acidic areas), and
Staphylococci (moist areas)
What is melanogenesis
physiological process of producing melanin, the light-absorbing pigment that is
responsible for the human skin and hair colouration.
How do melanocytes work to produce melanin
Melanocytes use a three-step “manufacturing” process to synthesise and disperse melanin throughout the
skin:
* Step 1: Activation; chemical signals coming from other cells in the skin cause the melanocyte to
“activate tyrosinase and begin melanin synthesis.
* Step 2: Synthesis; melanin is manufactured, “packaged” into containers called melanosomes, and
relocated to the outer regions of tentacle-like projections of melanocytes called dendrites.
* Step 3: Expression; melanin filled melanosomes are transferred from the ends of dendrites to
keratinocytes for shipment to the surface of the skin.
* Melanin accumulates in keratinocytes, where it ensures its photocarcinogenesis (cancer related to light)
preventive role.
* Melanin biosynthesis plays a crucial role in skin protection by shielding it from the effect of sunlight
(particularly UV, but other wavelengths in the electromagnetic spectrum are also linked to skin damage)
and ion accumulation, as well as by reactive oxygen species (ROS) trapping, where melanin acts as an
anti-oxidant.
What is the difference in skin colour due to
How active melanocytes are
How much melanin is synthesised
How efficiently melanin filled melanosomes are transported to keratinocytes
What are the two types of melanin
Eumelanin provides the brown tones in the skin and is found more abundantly in darker complexions.
It provides excellent protection from the sun by positioning itself at the top of the cell covering the
nucleus, which is where the DNA is found. The melanin protects the DNA by absorbing oxygen
radicals produced by UV radiation and prevents DNA damage that may lead to skin cancer. In blackskinned individuals, the abundant eumelanin protects the DNA and skin cancer is rare.
* In persons with red hair and fair skin, the main melanin that is produced is phaeomelanin which is
more reddish in colour than the brown eumelanin and accounts for the pink/orange skin colour and red
hair. Phaeomelanin is less effective at protecting the DNA from sun damage and consequently persons
with very fair complexions are more prone to skin cancers.
Difference between hypopigmentation and hyperpigmntation
Hyperpigmentation phenomenon such as lentigo, melasma, pigmented freckles, and acne scars are
characterised by the darkening of a skin area caused by the overproduction of melanin.
* Hypopigmentation, on the contrary, corresponds to the loss of skin colour, caused by melanocyte or
melanin depletion, or a decrease in L-Tyrosine.
* Manifestations of photoageing appear to be greatly i
Characteristics of baby skin
delicate and fragile, prone to inflammatory conditions like nappy/diaper rash.
Structure of baby skin
Baby skin has a 30% thinner stratum corneum and 20-30% thinner epidermis, higher cell turnover rate in the epidermis, and lower water barrier function. The amount of lipids in baby skin is less than in adult skin, requiring careful formulation rules for baby skin care products. Harsh cleansers can easily affect the delicate skin barrier, allowing easy penetration of irritants and microbial infections.
Characteristics of teenage skin
Some of the same hormones that cause the body to change also cause the body to begin producing
more sebum in the skin.
* This increase in sebum is a contributing factor to oily skin and the development of acne.
What is the principal function of stratum corneum
Restrict the loss of water to external environment
What does an alteration of the barrier
Cause an increase in transepidermal water loss (TEWL) in that water is lost faster than it can be replaced from the underlying tissues
What are the symptoms of dry skin
Flaking, chapping and a feeling of roughness over skin surface and itchy
What happens if moisture of content of skin is very low
The skin cracks and becomes red and inflamed making it susceptible to infection from microorganisms
What does the water content of the stratum corneum control
softness and pliability; a hydrated stratum
corneum is flexible and pliable, while a dehydrated stratum corneum is rigid, dry and cracked
What is the optimal water content of the stratum corneum
15% and 20% by weight. When the moisture content of the skin drops below 10%, it begins to feel “dry”.
What are the causes of low humidity
Air conditioning
Heat systems
High winds
Excessive sun exposure
What two major components of the stratum corneum that allow it to control TEWL
Natural moisturising factor (NMF)
Lipids
What is the natural moisturising factor made up
Amino acids
Urea
Pyrrolidone carboxylic acid
Lactic acid
Sugars
Peptides
What are amphoteric surfactants known for
Mildness on skin
What is oily skin a result of
Increase activity of sebaceous glands, which overproduce excessive quantities of sebum
What does sebum consist of
Triglycerides
Free fatty acids
Wax esters
Squalene
Cholesterol
Esters
What factors contribute to oily skin
Genetic inheritance
Hormonal change
Diet
Stress
External agents - chemicals , U.V
Puberty
Menstrual cycle
Oral contraceptives
Pregnancy
Why does acne occur
Sebaceous filaments are target sites for acne. The pathophysiology of acne centres on interplay of follicular hyperkeratinisation, increased sebum production, action of Propionibacterium acnes
Formation of comedones
Acne begins when the sebaceous ducts become plugged with keratinocytes. Just as skin cells on
the skin surface are constantly being sloughed off and renewed by the process of desquamation,
corneocytes are sloughed off the skin inside the pore as well. When sebum and corneocytes get
trapped in the narrow opening of the pore, this can cause cells to clump and form a comedone.
* Comedones may be microscopic or evident to the eye as blackheads or whiteheads.
* Sebum can build up and distend the follicle, and P. acnes proliferates in the sebum. The body responds
by sending lymphocytes and phagocytic cells to fight P. acnes and consequently the skin becomes
inflamed with pustules, papules, nodules, and/or cysts
Potential causes of sensitive skin
Hereditary factors
External factors - climate, U.V exposure, water, alkalis , solvents, skin peels
Symptoms of sensitive skin
Redness , swelling, scaling , tight, itch
What is dandruff
Scalp condition where visibly excessive scalp scaling
What is the process of dandruff
skin shedding is abnormal, and more regular than usual
skin on the scalp can produce excess sebum, which causes the growth of a fungus known as
Malassezia (previously known as Pityosporum)
This fungal species feeds on sebum and secretes certain lipids that affect the stratum corneum, causing
the cells to be irritated and shed off more rapidly than it can regenerate.
* Dead skin cells build up on the scalp, stick together, and then break off into larger, more visible flakes
How can dandruff be controlled / eliminated
using anti-fungal active ingredients such as Zinc Pyrithione, Coal Tar and Selenium Sulfide
What is an inflammatory reaction
physiological answer of the body to exogenous (external, such as UV light, heat, cold, acids, or bacterial attack) or endogenous (internal, such as an immune reaction)
stimuli.
Four clinical symptoms that characterise inflammation
Redness
Odema
Heat
Pain
What steps do inflammatory reactions occur
initiation phase, amplification phase, and
repairing phase
Cytokines in inflammatory responses
Cytokines play a key role in inflammatory processes. Cytokines are chemical mediators secreted by
activated cells that affect other cells, usually by binding to cell-surface receptors to modulate activity, including stimulation or inhibition of cell secretion, division and migration
Morphological changes in aged skin
Impaired proliferation, differentiation, desquamation and apoptosis of keratinocytes
Slow replacement of lipids
Flattening of the dermo-epidermal junction
Decrease and heterogeneity of melanocytes
Decrease of Langerhans cells
Reduction of dermis thickness, decrease of fibroblasts
Atrophy of the extracellular matrix
Reduction and disintegration of collagen and elastic
fibers, deposition of exogenous substances
Reduction of skin microvasculature
Decrease of sebaceous glands, sweat glands
Thinning of subcutaneous fat
Reduction of nerve endings
functional changes in aged skin
Disturbed barrier function
Decrease in surface contact area, increased risk of
separation by shearing forces
Greying of hair, age spots
Diminished skin immune function
Reduced strength and resiliency
Reduced strength and resiliency
Sensitisation to deformational forces, fine wrinkle
formation
Disturbed thermoregulation and supply with nutrients
Decreased lipid and sweat production
Reduced insulation and energy production
Disturbed sensory function
What factors affect aging of skin
intrinsic factors (genetically programmed changes) and extrinsic ageing caused by environmental factors, in particular UV-light exposure.
exogenous factors are exposure to cigarette smoke, airborne particulate matter
(pollution), infrared radiation, ozone and malnutrition.
What does UV radiation do to skin
Results in photoageing
UV radiation can cross the epidermis and reach the upper dermis where it
interacts with cellular chromophores, leading to DNA damage and increased oxidative stress.
* The biological effects of UV-radiation are based on light absorption in chromophores and the
subsequent conversion of energy in chemical reactions.
* Short wave UVB is mainly absorbed in the epidermis, generating DNA-damage by forming
photocarcinogenic cyclobutane pyrimidine dimers (CPDs).
* UVA-light is absorbed by cellular chromophores, such as urocanic acid, melanin precursors and
riboflavin.
* These light-exposed chromophores generate reactive oxygen species (ROS) including superoxide
anion and hydrogen peroxide, which damage lipids, proteins and DNA
How do ROS’S appear on skin
Wrinkles
* Rough skin texture
* Uneven skin tone
* Skin dullness
* Visible pores
* Blotches and age spots
* Skin dryness
What are wrinkles and why do they occur
depressions in the skin’s surface that may be classified as either coarse or fine, depending
on their depth
occur because of a reduction in muscle mass and skin thickness. This is accompanied by a
loss of elasticity and a restructuring of the dermal collagen and elastin along with dehydration of
the stratum corneum
What are age spots and what contributes to them
solar lentigo lesions , melanocytes tend to cluster together resulting in patches of pigmentation.
UV light stimulates melanocytes to produce
melanin. UV light can also penetrate the skin and damage melanocyte DNA, which can stimulate
melanocytes to enlarge and cluster together.
How does smoking affect the skin
Constricting blood vessels, limiting the amount of oxygen and other nutrients skin receives.
* Dehydrating the stratum corneum, leading to dry skin.
* Depleting levels of antioxidants, which are necessary to neutralise skin damaging free radicals.
* Decreasing skin firmness and increasing skin sagging.
* Interfering with the ability of fibroblasts to manufacture collagen and the extracellular matrix,
the structural framework for skin that is vital for repairing skin injuries.
* Affecting the body’s immune system, increasing the chance of developing skin cancer
How does pollution affect the skin
extrinsic skin ageing.
How are products effective to counter effects of atmospheric pollution
Incorporate adequate levels of antioxidants.
* Have a gentle cleansing action to remove grime.
* Aim to balance the natural oil levels of the skin.
* Strengthen the barrier function of the skin.
* Provides good moisturising properties.
* Normalise skin pH by ensuring that the pH of the product is in the range 4-6.5, like that of skin
Age related epidermal changes
flattening of the dermal
papillae which is accompanied by a decrease in dermal-epidermal cohesion which results in an
easier separation of the two layers in ageing skin as well as, a decrease in the connecting surface
area.
This loss of surface area may lead to increased fragility of the skin and less nutrient transfer
between dermis and epidermis.
Cell effects for epidermis - age related
reduction in the number of melanocytes; there is a decline
of 6-8% per decade after age 30, which accounts for the lighter skin colour with ageing and a
diminished protective capacity against UV exposure
decline in the number of melanocytes is similar for both sun protected and exposed tissue.
The reduction in melanin along with impaired melanosome transfer into keratinocytes, accounts
for the mottled pigmentation so characteristic of photoaged skin
a reduction in moisture content of the stratum corneum as skin ages. This
is most likely due to a reduction in the stratum corneum lipids which results in an inefficient ability
to bind and retain water.
What happens to fibroblasts in aged skin
Fibroblasts, the cells responsible for the biosynthesis of collagen, elastin and glycosaminoglycans
including hyaluronic acid, degenerate, slowing down production of new protein and
glycosaminoglycans which may account for the overall dermal atrophy in aged skin and its inability
to repair itself as quickly
