FUNCTIONS OF SKIN

TRANS EPIDERMAL WATER

LOSS

CUTANEOUS MICROFLORA

Dr. Swetha Saravanan

FUNCTIONS OF

SKIN.

FUNCTIONS OF SKIN

1. Permeability barrier.

2. Barrier to microorganisms, chemicals

3. Mechanical barrier

4. Immunlogical functions

5. Temperature Regulation

6. UV Radiation Protection

7. Autonomic & Sensory Function

8. Vitamin D synthesis

9. Sociosexual communication

Permeability Barrier

• Epidermis (St. Corneum) – PHYSICAL BARRIER

• Performed - St Corneum , Protein rich cells

embedded in LIPID rich matrix.

• Prevents - polar molecules

• Cant prevent -non polar , slow it.

• Factors- age, environmental changes,skin

continuity

Barrier to Microorganisms ; Chemicals

• Sebacceous lipids- Anti – microbial property

• Glycophospholipids, FFA (St. Corneum)- anti

bacterial effect

• AMP’s- broad spectrum anti microbial ,1st line

defence

a. Gram +ve c. Fungi

b. Gram –ve d. Virus

• AMP’s- produced in regions of hair follicle &

sweat glands

AMP (a) In normal skin, small amounts of AMPs are produced by the epidermis and are concentrated around hair follicles and in sweat glands. (b) After injury or infection, keratinocytes increase synthesis of AMPs and further AMPs are produced by neutrophils that are recruited as part of the acute inflammatory response.

Mechanical Barrier

• Skin- compressed , elastic

• Presence of ground substance, collagen,

elastic fibres

• Influenced by hydration , humidity.

• These properties prevent injury due to blunt

objects, pressure.

Immunological Functions

• Epidermis- Keratinocytes , Langerhans cells

• Dermis- T Lymphocytes

• Sweat glands & oil glands secretion-

a. Sweat – Inc. pH, salt,lysozyme,

AMP’s – 1st line of defence

b. Lipids

• Recognition of exogenous antigens, elicitation

of antigen- specific cell responses.

• Immune dysfunction –

Immunobullous disorders

Allergic contact dermatitis

Atopic dermatitis

Psoriasis

Mycosis fungoides.

TEMPERATURE REGULATION:

• Sensory input –thermoregulation

• Functions to permit heat loss/ reservation

• Thermoreceptor cellsHypothalamus

inhibition of sweating( eccrine glands)

or stimulation of shivering

• Blood supply of dermis – important for

temperature regulation

• A-V shunt system- enables the blood flow

to an extensive ,superficial venous plexus

• More at the feet, hand ,lips ,nose ,ear.

UV Radiation

UVA- epidermis -

sunburn, premature

ageing of skin, skin

cancer.

UVB- deeper dermis-

Chronic sun damage,

ageing and cancer

development

• Barrier Mechanisms-

1. Melanin production in epidermis

2. Protein barrier in the stratum Corneum.

• MOA-

Absorbing the radiation & minimizes DNA

& its other cellular constituents absorption

(lipids, urocanic acid)

Sensory & Autonomic functions

• Dense, 3-D network of highly specialized

afferent sensory , efferent autonomic nerve

branches.

• Detects- touch , vibration, pressure,

temperature changes , pain & itch.

• Glabrous , hairy skin - different types of

mechanoreceptors.

Superficial- Different types for glabrous & non

glabrous hair –small receptive field.

Deep- Same for both – large receptive field.

• Thermal sensation

Corresponding receptors for warmth &

cold sensation

• Mechanical Sensation

Mechanical nociceptors are present.

Vitamin D synthesis

• Synthesized in

skin.

• Essential for bone

metabolism.

Sociosexual communication

• Provides visual appeal, smell, feel.

• Important role in social, sexual

communication.

• Skin, hair, nails- decorative value.

• Cosmetics & clothes enhance appearance.

TRANS EPIDERMAL

WATER LOSS.

(TEWL)

• TEWL is the water loss through intact SC.

Not through sweat glands

Not through follicles.

DAMAGED

SKIN

Takes place – diffusion, evaporation.

In mammals – insensible water loss –

little physiological control.

Identify skin damage (chemicals, burns,

path causes, physiological causes)

TEWL proportional DAMAGE .

FACTORS INFLUENCING

Environmental factors- humidity,

temperature, seasonal variation.

Sweat gland activity

Metabolic activity.

TEWL – important for evaluating barrier

functioning.

TEWL measurements –discover disturbances -

skin protective function.

Typical fields- allergic tests, supervision the

healing process of skin damages & burns,

testing the effectiveness & biocompatibility of

cosmetic products.

CUTANEOUS MICRO

FLORA

WHAT’S CUTANEOUS MICRO

FLORA?

• Microorganisms that are commonly found on

OR in the body sites of an healthy person.

• Acc. to estimate- 10 10 bacteria.

• Based on type of skin- micro flora varies.

• Prevent colonisation – pathogens & possible

disease – bacterial interference.

Competitive binding receptors sites on

host cells –

• Nutrition.

• Mutual inhibition by metabolic or

toxic products or antibiotics

materials.

RESIDENT:

1. Presents invariably/months in a

particular site

2. Reduced by washing but not eleminated

3. If disturbed- transient flora – colonises

INFECTION

TRANSIENT:

1. Present briefly, rest on body surface but

do not persist.

2. Eliminated on washing.

3. Little significance- normal resident is

intact.

Normal flora is not static, constant

change

Depends on :

1. Age

2. Nutritional status of the site

3. Disease state

4. Drug or antibiotic effects

5. pH

6. Oxidation – reduction potentials

DISTURBED BALANCE

Lead to INFECTION

MICROBIAL DISEASE OF THE

SKIN MAY RESULT FROM:

• Breach of intact skin.

• Skin manifestation of systemic

disease.

• Toxin mediated skin damage.

Factors Influencing Flora Growth:

• Dryness

• pH

• Temperature

• Presence of nutrients

• Presence of inhibitory substance

DRYNESS

1. Inhibits micro-bacterial growth.

2. Dryness – bacteria enter dormant state or

die.

3. Moisture area – Large population

( axilla, perineum ,between toe’s & scalp).

LOW pH

• Skin -3 – 5pH

• Low pH inhibits growth for many kinds of

organisms

INHIBITORY SUBSTANCE

• Several bactericidal or bacteriostatic present

in normal skin

• Sweat gland secrete lysozyme & enzyme –

destroys peptidoglycan of bacteria wall.

DIRECT ENTRY INTO SKIN OF BACTERIA AND FUNGI

STRUCTURE INVOLVED INFECTION COMMON CAUSE

NAIL FLORA

• Similar to skin.

• Additionally, dust & extra material – trapped.

• Commonly-

1. Aspergillus

2. Penicillium

3. Cladosporium

4. Mucor

ADVANTAGES OF NORMAL FLORA

• Skin bacteria produces fatty acid -

discourages other species.

• De-squamination of epithelium.

DISADVANTAGE

• Organisms from perianal region ascend

the urethra Urinary tract Infection.

SUMMARY

FUNCTIONS OF SKIN.

• Permeability barrier.

• Barrier to microorganisms, chemicals

• Mechanical barrier.

• Immunological functions.

• Temperature Regulation.

• UV Radiation Protection.

• Autonomic & Sensory Function.

• Vitamin D synthesis.

• Sociosexual communication.

TRANS EPIDERMAL WATER LOSS

• TEWL is the water loss through intact

SC.

• FACTORS INFLUENCING-

1. Environmental factors- humidity,

temperature, seasonal variation.

2. Sweat gland activity

3. Metabolic activity.

• Evaluating barrier functioning.

• Typical fields-

Allergic tests,supervision the healing process of

skin damages & burns, testing the effectiveness

& biocompatibility of cosmetic products.

CUTANEOUS MICRO FLORA.

• Microorganisms that are commonly found on OR

in the body sites of an healthy person.

• Prevent colonisation – pathogens & possible

disease – bacterial interference.

• Normal flora - transient or resident.

• Its is not static, constant change.

• Microbial disease of the skin may result …..

Factors Influencing Flora Growth:

• Dryness

• pH

• Temperature

• Presence of nutrients

• Presence of inhibitory substance

• NAIL flora – similar to skin,Additionally – dust is trapped.(APCM)

• ADVANTAGES- Discourages other species, desquamination.

• DISADVANTAGES-Organisms in perianal region- UTI.