Skin

• Functions of the Skin

  • Acts as first line of defense
  • Prevents excessive fluid loss
  • Controls body temperature
  • Active in sensory perception
  • Important as defense against environmental hazards
  • Synthesizes vitamin D
• Normal Skin

  • Epidermis - avascular (lacks blood vessels and nerves)
  • Dermis
  • Subcutaneous tissue (hypodermis)
• Layers of the Epidermis(deep to superficial)

  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum lucidum
  • Stratum corneum
• Epidermis


  • Keratin - Waterproofing of the skin
  • Melanin - Skin pigment, determines skin color, production depends on multiple genes and environment
• Albinism


  Lack of melanin production
• Vitiligo


  Small areas of hypopigmentation
• Melasma


  Patches of darker skin
• Dermis


  • Connective tissue containing elastic and collagen fibers, provides flexibility and strength
  • Contains nerves and blood vessels
  • Includes sensory receptors for pressure, touch, pain, heat, cold
• Appendages of the Skin

  • Hair follicles
  • Sebaceous glands - Produce sebum, secretion increases at puberty
  • Eccrine sweat glands - All over body
  • Apocrine sweat glands - Axillae, scalp, face, external genitalia
• Hypodermis


  • Beneath dermis, connective tissue, fat cells, macrophages, fibroblasts, larger blood vessels, nerves
• Resident (Normal) Flora of the Skin is a mixed flora with components differing in various areas of the body. Microbes also reside under the fingernails, in hair follicles, and in glands. Opportunistic infections may occur because of injury or other inflammatory lesion. Infection may spread systemically from skin lesions.
• Skin Lesions


  The physical appearance of the lesion is necessary to make a diagnosis. Skin lesions may be caused by systemic disorders, localized factors.
• Types of Skin Lesions

  • Location
  • Length of time lesion
  • Changes occurring over time
  • Physical appearance - Color, elevation, texture, type of exudate
  • Presence of pain or pruritus (itching)
• Pruritus (itching)


  Associated with allergic responses, chemical irritation, insect bites, infestations by parasites (e.g. scabies). Mechanism not totally understood, release of histamine in a hypersensitivity response causes marked pruritus. Infection may result from breaking the skin barrier. Caused by scratching.
• The Sarcoptes scabiei mite causes scabies. Scabies spreads most often through direct contact with an infected person.
• Diagnostic Tests for Skin Lesions


  • Culture and staining of specimens
  • Biopsy
  • Blood tests
  • Skin testing using patch or scratch method
• General Treatment Measures


  • For pruritus - Topical agents to reduce sensation, antihistamines or glucocorticoids, avoidance of allergens
  • For infections - Antibiotic treatment
  • For precancerous lesions - Surgery, laser therapy, electrodessication, cryosurgery
• Electrodessication


  A little needle shaped electrode is manipulated by a dermatologist, which heats the skin in pinpoint precision to close blood vessels, stop bleeding and cauterize the wound.
• Contact Dermatitis


  Dermatitis is a general term that describes a common skin irritation. Exposure to an allergen (metals, cosmetics, chemicals, plants) causes a pruritic rash to develop at the site a few hours after exposure. Can also be caused by direct chemical or mechanical irritation.
• Pathophysiology of Contact Dermatitis

  • Sensitization occurs on first exposure, subsequent exposure results in manifestations of pruritic rash. Location of lesions is a clue to identify the allergen.
• Removal of the irritant and reduction of inflammation with topical glucocorticoids is the treatment for contact dermatitis.
• Urticaria (Hives)


  Result of type I hypersensitivity, caused by ingestion of substances like shellfish, drugs, certain fruits.
• Signs and Symptoms of Urticaria

  • Lesions are highly pruritic, found on the skin and may be scattered all over the body, occasionally in pharyngeal mucosa which can cause airway obstruction.
• Treatment for Urticaria


  • Over-the-counter antihistamines
  • Corticosteroids - with inflammation of the airways
• Atopic Dermatitis (Eczema)


  Atopic - inherited tendency, common problem in infancy. Rash is erythematous, with serous exudate, commonly occurs on face, chest, and shoulders. In adults, rash is dry.
• Pathophysiology of Atopic Dermatitis


  • Chronic inflammation results from response to allergens, eosinophilia and increased serum IgE levels. Affected areas become sensitive to irritants like soaps, temperature changes. Potential complication is secondary infections due to scratching.
• Elimination of aggravating agents, topical glucocorticoids, and antihistamines are the treatment for atopic dermatitis.
• Psoriasis


  Chronic inflammatory skin disorder, believed to be genetic in origin, causes a rash with itchy, scaly patches, most commonly on the knees, elbows, trunk and scalp.
• Pathophysiology of Psoriasis


  • Onset usually in the teenage years, marked by remission and exacerbations, results from abnormal T cell activation, excessive proliferation of keratinocytes leading to thickening of the dermis and epidermis.
• Signs and Symptoms of Psoriasis


  • Red patches of skin covered with silvery scales
  • Small scaling spots (commonly seen in children)
  • Dry, cracked skin that may bleed
  • Itching, burning
  • Thickened, pitted, or ridged nails
  • Swollen and stiff joints
• Treatment for Psoriasis


  • Glucocorticoids
  • Exposure to sunlight
• Pemphigus


  Autoimmune disorder, mainly two forms - Pemphigus vulgaris and Pemphigus foliaceous. Severity varies among individuals.
• Pathophysiology of Pemphigus


  • Autoantibodies disrupt cohesion between epidermal cells, causing blisters (bullae) to form. Skin sheds, leaving area painful and open to secondary infection. May be life-threatening if extensive.
• Signs and Symptoms of Pemphigus

  • Blisters in mouth
  • Blisters spreading to the skin, painful but not pruritic
  • Breathing difficulty due to swollen mouth and throat
• Systemic glucocorticoids and immunosuppressants are the treatment for pemphigus.
• Skin Infections


  May be caused by bacteria, viruses, fungi, other types of microbes, parasites. Opportunistic microbes can cause infections in minor abrasions or cuts. Serious infections may develop. Causative organism needs to be identified for appropriate treatment.
• Types of Bacterial Skin Infections

  • Primary - Often caused by resident flora
  • Secondary - Developing in wounds or pruritic lesions
• Cellulitis (erysipelas)


  Infection of the dermis and subcutaneous tissue, usually secondary to an injury, caused by Staphylococcus aureus or Streptococcus, frequently in lower trunks and legs, especially in individuals with restricted circulation in the extremities or immunocompromised. Area becomes red, swollen, and painful.
• Furuncles (Boils)


  Usually caused by Staphylococcus aureus, begins at hair follicles, frequently on the face, neck, back, can result in spread of infection to other areas of the skin due to draining of large amounts of purulent exudate.
• Signs and Symptoms of Furuncles

  • Red lesion
  • Painful nodule which often develops into a large, painful abscess
  • Abscess produces large amounts of purulent exudate (pus)