Dermatology - Lecture 9 Flashcards
Name the skin layers and their cells
Epidermis- Keratinised stratified squamous epithelial cells, and contain keratinocytes, melanocytes, Merkel cells
Basal Membrane- thin adhesive layer
Dermis- strong flexible, contains NN, VV, AA and lymphatics
Types of primary skin lesions and examples
- Macule (discoloured spot- Freckle) /Patch
- Papule (sharp borders- Mole)/ plaque (large elevated surface= Psoriasis) / nodule (wart) or tumor (large lipoma) / wheal (localised area edema- Hive, insect bite)
- Vesicle (elevation with fluid- blister, caused by herpes simplex)/ Bulla(large elevation with fluid- Large friction or burn blister)/ Pustule (vesicle or bulla filled with purulent fluid- acne, carbuncles)
Types of secondary skin lesions and examples
- Scale (dandruff)
- Crust (residue of impetigo)
- Fissure (athletes foot)
- Ulcer (pressure ulcer)
Dermatitis and types
inflammatory skin lesion
- Infective -bacteria (impetigo or folliculitis) , viruses (herpes), Parasite (scabies)
- Non-specific -eczematous dermatitis (Atopic dermatitis-hereditary or environmental, Contact Dermatitis- irritant or allergic, Gravitational Dermatitis- poor venous return in legs, Seborrhoeic dermatitis- irritant from yeast toxin on scalp & face)
- Characteristic - Psoriatic, lichenoid
Acute Dermatitis
Immune response causes dilation and lymphocytic infiltrate= Red (erythema) & Itchy (pruritus) from inflame reaction to irritant (scratching leads to secondary trauma)
Spongiosis (fluid accum. between epidermal cells= vesicle formation)
Chronic Dermatitis
Chronic trauma to acute dermatitis
Thickened, cracked and scaly skin= Hyper keratinisation
Increased cells in Stratum spinosum-Epidermis (Acanthosis) = increased fibrosis in dermis
Constant picking of hyper-keratinised cells = localised thick, keratanised lesions “prurigo nodularis”- can lead to ulcer
Lichen Planus (Dermatitis)
Common inflame. D of skin
Characterised by shiny, flat topped, firm papules, purple in colour with fine white lines (wick hams striae)
Seen on front of wrists, lower back and ankles or on mucous membranes
Resolves after 18months
Damages basal layer of epidermis, scales form and lymphocytes infiltrate close to basal layer “Lichenoid pattern”
Psoriasis (Dermatitis)
Chronic intermittent D, 2% population, mild to severe
S+S: Raised (acanthosis) red plaques (oedematous & capillary dilation) covered by white scale (hyperkeratosis), and mostly symmetrical
Aet: poorly understood, partially genetic. linked to joint pain
Path: infiltrate mostly neutrophils
Bacterial Skin Infections
- Impetigo (school sores)
- Bacterial folliculitis
- Erysipelas (streptococcal infect.)
- Cellulitis
Impetigo- staphylococci, contagious, mostly with kids, large bullae, honey coloured crusted exudate, pruritus
Folliculitis- hair follicules, tiny pustules, boil formation
Erysipelas- streptococcal infection and spreads through lymph system, acute inflame deep dermis, common lower limbs or face, well defined border
Cellulitis-
Cellulitis
bacterial infection to skin
Or Periorbital Cellulitus (swollen eyes)-
Eit: streptococal or staphyloccocal bacteria entering cut to skin (bite, scratch) or Periorbital via sinuses or throat
S+S: sudden clearly defined area on skin red and tender.
Bright red, shiny, swollen, hot.
Can be accompanied by fever, chills, HA, nausea, swollen lymph nodes.
Risk factors: Problematic circulation, Diabetes, Pregnancy, Alcoholism, Obesity.
Tx: Antibiotic Tx immediately- norm 10days
Viral skin Infection
- Herpes virus
- Shingles (herpes zoster-varicella)
- Human papillomavirus (warts)
Herpes- blistering lesions, after infection virus persist in dorsal root ganglion in latent state, no cure. Herpes simplex I (non genital), II (genital), III (chicken pox/shingles)
Shingles- from dormant virus in DRG from chic pox, affects skin of corresponding dermatome creating vesicles, burning pain & tingling. P still present after rash gone.
Human Pap- 50 types benign epithelial tumour. genital W increase risk of cancer
Fungal skin Infections
- Trichophyton
- Microsporum
- Epidermophyton
- ring worm or tinea
40 species fungi, spores live up to yr on skin, reffered to as ‘ringworm’ or ‘tine’
Normally superficial infection. subcutaneous rare
Fungal hyphae or yeast resides in Keratin layer= little inflame response
sometimes infect hair follicle and will increase inflame response
Dermatological pathologies
Dermatitis Acute vs. Chronic Lichenoid Planus and Psoriasis Infection Viral Herpes Zoster, Shingles and Human Papillomavirus (HPV) Fungal Bacterial Impetigo and Cellulitis
Basal Cell Carcinomas
- Character
- 3 x types
-Develop from keratinocytes in basal layer
-linked to UV exposure
-local invasion but rare metast.
-lesions erode deep into tissue ‘rodent ulcer’
Nodular
Morphoeic
Superficial
Nodular BCC
- most common, in over 50s mostly, on forehead & face
- Firm, raised nodule, may centrally ulcerate and sink
- Shiny, pearly raised spot
