SKIN Flashcards
Normal proliferation of the skin occurs
just in the basal layer
Function of skin
- Barrier to infection
- Thermoregulation
- Protection against trauma
- Protection against UV
- Vitamin D synthesis
- Regulate H2O loss
Basic Layers of skin
- Epidermis
- dermis
- Subcutaneous tissue
Outermost layer of epidermis
Outermost layer known as the stratum corneum
What is epidermis made up of
Made up of corneo-desmosomes and desmosomes
Function of corneo desmosomes
Corneo-desmosomes (known as adhesion molecules) keep the corneocytes together
Increased numbers of corneodesmosomes are seen in diseases such as
psoriasis in which there is a thickening of the stratum corneum
Decreased numbers of corneodesmosomes are seen in diseases such as
atopic eczema in which there is a thinning of the stratum corneum - meaning there is an increased risk of inflammation
Function of filaggrin
(derived from profilaggrin (a structural component of the cornfield envelope)) produces natural moisturising factor (NMF)
Corneocytes function
Corneocytes are filled with NMF which help maintain the skin’s hydration
- keeps H2O inside the skin
NMF function
- help maintain the skin’s hydration
- important in maintaining an acidic environment at the outer surface of the stratum corneum
desquamation
In order to balance the introduction of new cells in the basal layer of the epidermis, mature corneocytes are shed from the surface of the stratum corneum in a process called desquamation
Process of desquamination
involves the degradationof the extracellularcorneo-desmosomes under the action of protease enzymes
Why is The pH of normal skin 5.5
this allows the proteases to remain on the skin thereby enabling the balance of new cells from the basal layers of the epidermis (desquamation
Function of Lipid lamellae
- keeps water inside skin cells
- Irritants & allergens tend to “bounce off” the surface of the skin due to thepresence of the lipid lamellae
Function of stratum corneum
The normal & intact stratum corneum acts as an efficient barrier to the penetration of irritants and allergens and to the loss of water
Stratum corneum
outermost layer of skin
What is the brick wall model
The skin barrier can be explained using the brick wall model; whereby the corneocytes are the bricks, the corneodesmosomes are the iron rods & the lipid lamellae is the cement
Why is vitamin D important
Vitamin D is essential in producing the anti-microbial peptides necessary to defend the skin from bacteria & viruses
What do irritants do to the skin
Irritants break down healthy skin
What do allergens do to skin
Allergens trigger skin flare ups by penetrating into the skin and causing the skin to react
What are skin flare ups
All caused by allergens which are able to penetrate into the skin, where they are met with lymphocytes which release chemicals that induce INFLAMMATION:
3 products of skin flare up inflammation
- Red skin: Dilation of blood vessels - due to lymphocyte activity
- Itchy skin: Stimulation of nerves
- Dry skin: Skin cells leaking - due to lymphocyte activity
What is the effect of increased pH on skin
damage to the skin barrier since the corneodesmosomes become damaged by the increased pH resulting in the breakdown of the skin barrier and thus increasing the risk of infection
Why can pH of skin be increased
If profilaggrin and thus filaggrin are not present for any reason, there will be a lack of NMF meaning there will be less water retention in the corneocytes
How does acne occur (1)
In acne, hypercornificationof the stratum corneum occurs resulting in adherent cells (corneodesmosomes) blocking the entrance to hair follicles
What happens when the entrance of the hair follicles are blocked (2)
This results in the increased production of sebum by the sebaceous glands - causing the skin to feel greasy
What happens are the increased production of sebaceous glands as a result of the blocked hair follicles (3)
The increased sebum production eventually some of the sebum to become trapped in the narrowed hair follicle
This means that the sebum STAGNATES at the pit of the follicle where there is NO OXYGEN
What happens when the sebum stagnates at the pit of the follicle where there is no oxygen (4)
This provides anaerobic conditionswhich allow the propionic bacteriaacnes (p.acnes) to multiply in the stagnant sebum
What happens when the p acnes multiply in the stagnant sebum (5)
The p.acnes breakdown the triglycerides in sebum into free fatty acids resulting in irritation, inflammation and the attraction of neutrophils since the p.acnes release chemicals that attract them
What happens when the neutrophils go towards the pacnes (6)
This then results in pus formation and further inflammation since the no full hair follicle is rapidly filled with attracted neutrophils
How can cosmetics and oily hair gel trigger acne
Cosmetics & oily hair gel can triggeracne since they help “plug” the hair follicle and initiate the acne process - acne caused by these products is known as cosmetically induced acne
