introduction to dermatology part 2 Flashcards
(25 cards)
what are the functions of the hair?
Protection against external factors Sebum Apocrine sweat Thermoregulation Social and sexual interaction Epithelial and melanocyte stem cells
what are the thick hairs on scalp, eyebrows and eyelashes called?
terminal hairs
what are the hairs on the rest of the body called?
vellus hairs (not found on palms, soles, mucosal regions of lips and external genitalia) thinner
what are the phases of the hair cycle?
anagen
catagen
telogen
(then loss of hair)
outline the anagen phase
(where new hair forms and grows)
85% of hair; lasts 2-6 years
outline the catagen phase
(regressing phase)
1% of hair; lasts 3 weeks
outline the telogen phase
(resting phase)
10-15% of hair; lasts 3 months
what is the infundibulum?
Uppermost portion of the hair follicle extending from opening of sebaceous gland to surface of the skin
what is the isthmus?
Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
Epithelium keratinization begins with lack of granular layer named “trichilemmal keratinization”
what is the bulge?
Segment of the outer root sheath located at insertion of arrector pili muscle
Hair follicle stem cells reside here
Migrate:
Downward → generate the new lower anagen hair follicle → enter hair bulb matrix, proliferate and undergo terminal differentiation to form hair shaft and inner root sheath.
Upwards (distally) → form sebaceous glands and to proliferate in response to wounding
what is the bulb?
Lower most portion of the hair follicle, includes the follicular dermal papilla and the hair matrix
what is the outer root sheath?
Extends along from the hair bulb to the infundibulum and epidermis serves as a reservoir of stem cells
what is the inner root sheat?
Guides / shapes hair
Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fiber & capillary loop.
what are the functions of the nails?
Protection of underlying distal phalanx
Counterpressure effect to pulp important for walking and tactile sensation
Increase dexterity / manipulation of small objects
Enhance sensory discrimination
Facilitate scratching or grooming
what are the 2 main parts of the nail?
nail plate
nail matrix
what is the nail plate?
Final product of proliferation and differentiation of nail matrix keratinocytes Emerges from proximal nail fold Grows at 1-3mm/month Firmly attached to nail-bed Detaches at hyponychium Lined laterally by lateral nail folds
what is the nail matrix?
Produces nail plate
Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
Lunula only visible proportion
Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins
Also contains melanocytes
give an overview of psoriasis
Chronic, immune-mediated disorder
Polygenic predisposition combined with environmental triggers, e.g. trauma, infections, or medications
Pathophysiology involves T-cells and their interactions with dendritic cells and cells involvement in innate immunity, including keratinocytes
Sharply demarcated, scaly, erythematous plaques characterise the most common form of psoriasis
Common sites of involvement are scalp, elbows and knees, followed by nails, hands, feet and trunk (including intergluteal fold)
Psoriatic arthritis is most common systemic manifestation
outline the pathophysiology of psoriasis
Stressed keratinocytes release DNA / RNA → form complex with antimicrobial peptides → induce cytokines (TNF-α, IL-1 and IFN-α) production → activate dermal dendritic cells (dDCs)
dDCs migrate to lymph nodes → promote Th1, Th17, Th22 cells → chemokine release – migration of inflammatory cells into dermis → cytokine release → keratinocyte proliferation → psoriatic plaque
what are the clinical features of psoriasis?
red patches
scales of keratin
pitting of nails
oil stains on nails due to lifting
how is psoriasis managed?
reduce alcohol and smoking
Therapeutic ladder Topical therapies Vitamin D analogues Topical corticosteroids Retinoids Topical tacrolimus / pimecrolimus
Phototherapy
Narrowband UVB
PUVA (Psoralen + UVA)
Acitretin
Systemic immunosuppression
Methotrexate
Ciclosporin
Advanced therapies
PDE4 inhibitors (Apremilast)
Biologics (anti-TNF-α, anti-IL-17, anti-IL23)
JAK inhibitors
give an overview of atopic eczema
Intensely pruritic chronic inflammatory condition
Complex genetic disease with environmental influences
Typically beings during infancy or early childhood
Often associated with other ‘atopic’ disorders e.g. asthma, rhinoconjunctivitis
Acute inflammation of cheeks, scalp and extensors in infants
Flexural inflammation and lichenification in children and adults
Daily emollients and anti-inflammatory therapy are cornerstone of management
Eczema (dermatitis) - umbrella term: atopic eczema, seborrhoiec dermatitis, venous stasis eczema, allergic contact dermatitis, irritant contact dermatitis
outline the pathophysiology of atopic eczema
Barrier defect
Filaggrin - bind and aggregate keratin bundles and intermediate filaments to form cellular scaffold in corneocytes
Reduced extracellular lipids and impaired ceramide production
Increased transepidermal water loss (TEWL)
Impaired protection against microbes and environmental allergens
Immune dysregulation
Staphylococcal superantigens stimulate Th2 lymphocyte responses and subvert T‐reg
T-cell infiltrate - bias towards Th2 responses
Role of microbiome?
Eosinophils
what are the clinical features of atopic eczema?
Infantile phase atopic dermatitis: erythematous, oedematous papule & plaques ± vesiculation
thickening of skin and dispigmentation
fissuring
