Structure of the Skin

1. Structure of the Skin

2. Structure of the Skin • The largest organ of the body. Its surface area is responsible for the regulation of body temperature • Has three layers • Epidermis which contains keratinocytes. Keratinocytes contain keratin which is a strong tensile protein responsible for much of the skin’s physical barrier properties. • Dermis is the layer of the skin that contains blood vessels, immune cells and fibroblasts that produce collagen and elastin • Hypodermis contains a fatty layer where adipocytes are located. This is attached to the fascia of muscles

3. Functions of the skin • Provides a physical barrier to infections • Provides a barrier to lose of water • Temperature regulation via sweating • Enable the sense of touch • Vitamin D is synthesized from cholesterol

4. Immune function of skin • The skin is not a sterile environment. On the skin, bacteria and fungi are present. • The normal flora of the skin provides a competitive environment that protects against invasion against more pathogenic organisms • Skin contains immune system cells including lymphocytes (small degree), mast cells, and dendritic cells • Mast cells contain histamine and when the mast cells meet an antigen they release histamine to produce a “wheal and flare” reaction

5. Dendritic cells are similar to macrophages and they engulf foreign invaders and carry them to local lymph nodes where a immune response is triggered.

6. Diseases of the skin • Autoimmune diseases of the skin • Psoriasis. In psoriasis the immune system of the body attacks the cells of the upper layers of the skin. The patient develops rashes, intense erythema that leads to scales and blisters localized to plaques areas. Can be painful • Drugs that suppress the immune system are used • Topical steroid preparations: Desoximetasone (Topicort®), Fluocinolide (lidex®). • Coal Tar agents: Anthralin cream (Psoriatec®) • Topical immune system medications: Pimecrolimus (Elidel®) • Vitamin D derivatives: Calcipotriene (Dovonex®)

7. Eczema is similar to psoriasis but less severe • Eczema is believed to be a hereditary allergic reaction of the skin to a normally benign antigen(s) • Eczema is sometimes called “atopic dermatitis” and is commonly associated with asthmatic patients • Affected areas are itchy, red, and warm to the touch. Lesions may enlarge and become scaly. The rash are very itchy and the scratching can damage the skin further. • Treatment includes: • Topical Steroids • Vitamin D derivatives (Dovonex) • Vitamin A derivatives (retinoids): Differin® (Adapalene) • Topical immune modulators: Pimecrolimus (Elidel®)

8. Acne • Inflammatory reaction in the skin called by excessive production of sebum in the sebaceous glands of the skin located near hair follicles. • Bacteria known as Propriobacterium acnes feeds on the fats and release fatty acids which causes the skin to become inflammed • A severe form of acne is nodulocystic acne which can form life long scars • Therapy: • Benzoyl Peroxide (Oxy 10, Brevoxyl®, Acne 10®) • Topical antibiotics combined with benzoyl peroxide i.eBenzaclin ® is Clindamycin and benzoyl peroxide • Topical Vitamin A derivatives: Retin A® (tretinoin ) • Oral Contraceptive in females: Ortho Tri Cyclen® • Nodulocytic acne: Accutane ® (isotretinoin) A oral medication. • Must be registered in the FDA’s iPLEDGE system

9. Bacterial Infections • Most commonly seen infections are impetigo in children and folliculitis in adults • Both are caused by staphylococcal infections • Cured by penicillin type antibiotics: • Dicloxacillin 500 mg capule three times a day for 10 days

10. Viral Infections • Chicken Pox: Varicella Zoster Virus is the cause. Highly contagious by either touch or airborne sneezing. No medication really effective, sometimes acyclovir is tried in immunosuppressed patients. Calamine lotion® is effective in suppressing itch and crusting the lesions. • Measles: very contagious. caused by the respiratory virus Rubeola (not really a skin disease) • Shingles: Varicella Zoster virus is the cause. If this is seen in young patients it can mean HIV infection

11. Cancers of the skin • Any skin lesion that is large, raised, asymmetric, changes in color, and has raggy edges should raise the suspicion of cancer • Malignant melanoma is a cancer of the pigment producing cells of the skin and can be fatal if allowed to spread to other areas of the body • Basal Cell Carcinoma is a serious cancer; however, it can be cured with chemotherapy

12. Miscellaneous disorders of the skin • Wrinkles are caused by a lack of elastin in the skin and reduce sebum production. It is common in old age and sun exposed skin • Rosacea is also known as “adult” acne. Its cause is not known • Burns • Decibutus ulcers