Functions and Layers of Skin

Functions of the Skin

• The skin acts as the body's first line of defense, protecting it when unbroken.
• It prevents excessive fluid loss.
• The skin controls body temperature through cutaneous vasodilation, secretion, and sweat evaporation.
• It's active in sensory perception, defending against environmental hazards.
• The skin synthesizes vitamin D upon exposure to small amounts of ultraviolet light.

Review of Normal Skin

• The layers of the skin include:
  • Epidermis, which is avascular.
  • Dermis.
  • Subcutaneous tissue, also known as the hypodermis.

Epidermis

Five layers that vary in thickness are present.

• Keratin is responsible for waterproofing the skin.
• Melanin is the skin pigment that determines skin color, with production depending on multiple genes and the environment.
• Albinism is characterized by a lack of melatonin production.
• Vitiligo presents as small areas of hypopigmentation.
• Melasma results in patches of darker skin.

Layers of the Epidermis

• Stratum basale exhibits mitotic activity.
• Stratum spinosum has cells connected by desmosomes and undergoes protein synthesis.
• Stratum granulosum is where keratin formation begins.
• The layers of the epidermis include Stratum lucidum and Stratum corneum, which acts as a waterproofing barrier .

Dermis

• Connective tissue contains elastic and collagen fibers.
• The dermis is responsible for the flexibility and strength of the skin.
• The dermis contains nerves and blood vessels, including sensory receptors for pressure, touch, pain, heat, and cold.

Appendages of the Skin

• Hair follicles arise from the Stratum basale and are hair-producing, with the arrector pili muscle associated with each follicle.
• Sebaceous glands produce sebum, and their secretion increases at puberty due to the influence of sex hormones.
• Sweat glands are of two types:
  • Eccrine sweat glands are all over the body.
  • Apocrine sweat glands are in the axillae, scalp, face, and external genitalia.

Hypodermis

• The hypodermis located beneath the dermis includes:
  • Connective tissue.
  • Fat cells.
  • Macrophages.
  • Fibroblasts.
  • Larger blood vessels.
  • Nerves.

Resident (Normal) Flora of the Skin

• The skin contains mixed flora with components differing in various body areas.
• Microbes also reside under fingernails, in hair follicles, and in glands.
• Opportunistic infections may occur because of injury or other inflammatory lesions.
• Infections may spread systemically from skin lesions.

Skin Lesions

• The physical appearance of a lesion is necessary to make a diagnosis.
• Skin lesions can be caused by:
  • Systemic disorders, such as liver disease.
  • Systemic infections, like chickenpox.
  • Allergies to ingested food or drugs.
  • Localized factors like exposure to toxins.
• Lesion types are identified by:
  • Location.
  • Length of time the lesion has been present.
  • Changes occurring over time.
  • Physical appearance including color, elevation, texture, and type of exudate.
  • Presence of pain or pruritus (itching).

Common Skin Lesions

• Macule: Appears as a small, flat, circumscribed skin lesion with a varying color, in contrast with the encompassing skin.
• Papule: Appears as a small, firm and elevated skin lesion.
• Nodule: Appears as a palpable, elevated skin lesion with a varying size.
• Pustule: Appears as an elevated and erythematous lesion, frequently containing purulent drainage.
• Vesicle: Appears as an elevated, thin-walled lesion, containing clear fluid (blister).
• Plaque: Appears as a large, slightly eleveated of flat surfaced skin.
• Fissure: Appears as a small and deep, lineated crack or breakage in the skin.
• Ulcer: Appears as an area of the skin with a cavity and tissue loss, which may lead to weeping or bleeding.
• Erosion: Appears as an area of the skin with a shallow and moist cavity in the epidermis.
• Comedone: Appears as a mass of sebum, keratin, and debris blocking the opening of a hair follicle.

Pruritus

• Pruritus, or itching, is associated with allergic responses, chemical irritation from insect bites, and parasite infestations such as scabies.
• The mechanism isn't fully understood, but it involves histamine release in a hypersensitivity response, which causes marked itching and scratching.
• Infection can result from breaking the skin barrier.

Diagnostic Tests for Skin Lesions

• Culture and staining of specimens can identify bacterial infections through microscopic and direct observations, and specific procedures exist for identifying fungal or parasitic infections.
• Biopsies are performed to detect malignant changes, serving as a safeguard before or after removing skin lesions.
• Blood tests help diagnose conditions caused by allergies or abnormal immune reactions.
• Skin testing can be performed using a patch or scratch method.

General Treatment Measures

• Pruritus can be treated with topical agents to reduce sensation and may involve antihistamines or glucocorticoids.
• Allergens should be avoided to reduce the risk of recurrence.
• Infections may require antibiotic treatment.
• Precancerous lesions can be addressed with surgery, laser therapy, electrodessication, or cryosurgery.

Contact Dermatitis

• Exposure to allergens like metals, cosmetics, soaps, chemicals, and plants results in sensitization on first exposure and a pruritic rash within hours.
• Direct chemical or mechanical irritation doesn't involve an immune response, arises from direct exposure, and improves with irritant removal and topical glucocorticoids.
• Sensitization during the first time of exposure.
• Subsequent pruritus may be from poison ivy.
• Signs and symptoms of allergic dermatitis include a pruritic, erythematous, and edematous area often covered with small vesicles.
• Chemical irritation manifests as an edematous and erythematous area, which can be pruritic or painful.
• Treatment includes removal of the irritant followed by a topical glucocorticoids application.

Urticaria (Hives)

• Urticaria arises from type I hypersensitivity, often by ingesting substances like shellfish, drugs, or certain fruits.
• Characterized by eruption of hard, raised, erythematous lesions that are highly pruritic.
• Hives are found on the skin and may be scattered all over the body, or occasionally in the pharyngeal mucosa.
• May have airway obstruction.
• Treatment is usually over-the-counter antihistamines, corticosteroids for airway inflammation and Omalizumab for chronic cases in children over the age of 12.

Atopic Dermatitis (Eczema)

• Atopic dermatitis has an inherited tendency and is a common problem in infancy.
• In infancy results in an erythematous rash, with serous exudate, commonly occurs on the face, chest and shoulders
• In adults, the rash is dry, scaly, and pruritic, often on flexor surfaces.
• Pathophysiology comes from chronic inflammation from the response to allergens. Eosinophilia and increased serum IgE levels exist.
• Affected areas become sensitive to irritants like soaps, certain fabrics, and temperature changes.
• Secondary infections may occur as potential complications, especially due to scratching.
• Treatment involves eliminating the aggravating agent, topical glucocorticoids, and antihistamines.

Psoriasis

• Psoriasis is a chronic inflammatory skin disorder that affects 1% to 3% of the population and is believed to be genetic.
• Onset is usually in the teenage years, marked by remission and exacerbations, and cases vary in severity.
• The condition can present in red patches of skin covered with silvery scales. Small scaling sports are common in children.
• Other indicators include dry, cracked skin that may bleed, with itching, burning, soreness
• The fingernails usually become thickened, pitted and ridged. Swollen and stiff joints exist.
• Psoriasis results from abnormal T cell activation, leading to excessive keratinocyte proliferation and thickening of the dermis and epidermis, with shedding occurring in one day rather than two-week intervals.
• Treatment involves glucocorticoids, tar preparations, antimetabolic methotrexate in severe cases and exposure to sunlight.

Pemphigus

• Pemphigus is an autoimmune disorder.
• Mainly are two forms: Pemphigus vulgaris and Pemphigus foliaceous
• Severity varies between individuals.
• Autoantibodies disrupt epidermal cell cohesion, causing blisters (bullae) to form.
• Skin sheds, leading to painful open areas susceptible to secondary infection that can be life-threatening if extensive, like in Stevens-Johnson syndrome
• Blisters develop in the mouth and spreading to the skin, are painful, and not pruritic. Breathing difficulty may occur die to swollen mouth and throat.
• The treatment includes systemic glucocorticoids and immunosuppressants.

Scleroderma

• Scleroderma may occur as a skin disorder or systemically, affecting viscera with an unknown primary cause.
• Increased collagen deposition, inflammation, and fibrosis with decreased capillary networks are some effects.
• Scleroderma triggers renal failure, intestinal obstruction, respiratory failure, caused by tissue distortion.
• Hard, shiny, tight, immovable skin areas and narrowed, shortened fingertips are signs. Raynaud phenomenon can be present.
• Facial expression is lost due to skin tightening and impaired mouth and eye movement.
• The cutaneous form can affect microcirculation in organs, causing renal failure, intestinal obstruction, or pulmonary hypertension-induced respiratory failure.
• Treatment includes medications that vary based on specific manifestations.

Skin Infections

• Skin infections can be caused by bacteria, viruses, fungi, or other types of microbes.
• Opportunistic microbes are causes
• Infection may result from minor abrasions or cuts and may develop into serious infections, such that identifying causative organism is needed.
• Diagnostic tests are imperative to confirm treatment for causative organism.

Bacterial Infections

• Common to the skin are Primary bacterial infections, which are often caused by resident flora, and Secondary bacterial infections, which develop in wounds or pruritic lesions.

Cellulitis (erysipelas)

• Cellulitis is an infection of the dermis and subcutaneous tissue.
• Staphylococcus aureus , Streptococcus are indicative causative orgamisms
• Usually is secondary to a injury, and frequently seen in lower trunks and legs, especially in individuals with restricted or immunocompromised circulation.
• Reddened area, edema, and pain. Red streaks are seen along proximal areas of the limb and lymph vessels.
• This may occur as a result of restricted circulation in the extremities, in immunocompromised individuals. Area becomes red, painful, and swollen. Red streaks may occur.

Furuncles (Boils)

• Furuncles are usually caused by S. aureus , that begins at a hair follicle, and are common on the face, neck, back and frequently drain purulent exudate.
• Characterized as a firm, red lesion and painful nodule which often develops into a painful abscess.
• Squeezing lead to autoinoculation.
• Abscess produces a large amount of purulent exudate
• Carbuncles are collections of furuncles that coalesce from a infected mass.
• Treatment includes compresses to promote drainage, analgesics for pain relief, and cutting/draining the abscess followed by antibiotics.

Impetigo

• Impetigo are common in children and infant, may also occur in adults and is a highly contagious form of S. aureus particularly in neonates.
• Usually characterized as lesions on the face and transmitted through physical contact or fomites. Also pruritus is common.
• Leads to scratching and furher infection from bacteria.
• Small red visicles will erupt in the area. Forming yellowish crusted masses.
• Treated in early stages with topical antibiotics and is systemic if lesions are large. Antibiotic resistant strains of S.Aureus exist and may result in local infection.

Acute Necrotizing Fasciitis

• It is a mixture of aerobic and anaerobic bacteria usually found at infection side, and with severe necrosis and tissue inflammation.
• A virulent strain of gram-positive, beta A-hemolytic Streptococcus is indicative of infection.
• Bacteria secrete toxins that destroy tissue, leading to massive connective tissue damage that can lead to an extremity.
• Shows are marks of inflammation, pain rapidly increasing in size.
• Systemic manifestations are present such as fever, tachycardia, hypotension, mental confusion, disorientation and risk of organfailure.
• Dermal gangrene apparent on sight.
• Requires aggressive antimicrobial therapy, fluid replacement, excision if needed, high oxygen chambers and most likely an amputation to combat. If the infection prevails, tissue los and greater systemic toxicity will lead to morality.

Leprosy (Hansen Disease)

• Caused by infection of Mycobacterium leprae, where the chronic condition will be classified into three major types.
• Infection can occur on the peripheral nerves, skin and mucous membranes and cause damage to limbs.
• Mechanism and pathogenicity largely unknown.
• Is treated with microscopic examination of skin biopsy and antibiotics.

Herpes Simplex

• Herpes simplex virus can either be type 1 (HSV-1) or type 2 (HSV-2), where 1 usually stems from fevers and sores while 2 can result in genital herpes.
• The effect will be similar is both types with usually primary infection being asymptomatic.
• Infection can occur by direct contact, however transmission and infection can occur prior to appearance.
• Potential complications lead from keratitis to herpetic whit low with painful infection. Recurrence can be triggered by sun, cold and stress.

Verrucae (Warts)

• Human papillomavirus (HPV) types 1 to 4, and 6 and 11 typically develope in young adults and children.
• Spread occur by shedding the surface and may spontaneously disappear.
• Platar warts are common and genital warts such as types 6 and 11 can occur.
• Fungle infection diagnosis occur from skin scrapings.

Fungal Infections (Mycoses)

• Most fungal infections are usually superficial.
• Candida infection is associated with diabetes.
• May spread systemically in immunocompromised individuals
• Diagnostic exams are usually from microscopy of skin scrapings, and are examined to become florescent in ultraviolet light.
• Infection of the scalp, common in schoolchildren and erythema may be apparent during diagnosis. oral medicine may be required for symptoms.
• Tinea Coporis: infects the body, with exception of the hairy spots, leading to round spots and pruritic characteristics. Requires topical medications.
• Tinea Unguium: infects the nails specifically the toenails and cause the nails to turn white and thicken with cracks, usually spreads from other nails as well.

Tinea (Cont.)

• Tinea Pedis: Athletes foot and involved specifically around the toes. This is associated with swimming pools and gymnasiums, and may come part of the normal flora, which becomes opportunistic to the body. Topical antifungal medication and secondary bacterial infection can occur as well.

Other infections

• Scabies: invasion by mite Sarcoptes scabiei, where they burrow to lay eggs over period of weeks and die leaving larvea to burrow into the membrane and cause it to be pruritic with burrows appearing brown on sight. Scabies are intensly pruritic and burrow into skin via search of nutrients
• Pediulosis (lice: includes lice such as Pediculus Humanus corpois, Pediculus Humans Capitis, and Pediculus humans pubis.
• Lice typically lay eggs on the hair shafts and after hatching, where they bite humans for blood and cause scratching and excoriation in the area, along with ova production.

Keratoses

• Keratoses can stem from aged or skin damage.
• Seborrheic keratosis usually stems from proliferation of basal calls and elevations that be rough or smooth.
• Actinic Keratoses: Skin is exposed UV radiation of pigmented and scaly patches typically from those with a fairer skin tone.

Warning Signs of Cancer

• Wounds that do not heal and constant change in size, texture and change that continues to expand the surface.
• Skin develops new moles in all shapes and sizes.
• Skin will ooze discharge or itch.

Guidelines to reduce Skin Cancers

• Reduce constant expositure to sunlight.
• Covering up with clothing, wearing hats to protect the face and neck and using sunscreen or sunblock.
• Ensuring that infants do not have high exposure to sun.

Skin Tumors

• They can be from all types of microbes, parasites, bacterial, minor abrasion and opportunistic. Thus requires correct identification.

Squamos Cell Carcinoma

• Type of painless epidermis that is found on usually exposured portions of the skin and oral cavity.
• When removed before reaching advanced stages, they have excellent prognosis,
• These areas can rise from premalignant stages.
• Found on face as well as base of the tonuge.

Malignant Melanoma

• It is a high metastatic skin cancer form that leads with developments in melanocytes.
• Appears as multi coloured irregular in shape and color with quick enlargement.
• Treated with radiation therapy, chemotherapy and surgery.

ABCD of Melanoma

• Appearance.
• Border.
• Color.
• Diameter can all lead to the start of melanoma.

Kaposi Sarcoma

• Occurs for those with AIDS, immunodifficiencies, or other viruses and can affect the visceura, as swell as the skin.
• This usually effects the small blood vessels from purplish macules.
• Can develop rapidly over the patient on the upper extremities.
• Treated with combo for combinations such as radiation, chemotherapy or biological therapies.

Overview of the skin's functions, including protection, fluid loss prevention, and temperature control. Review of normal skin anatomy, including the epidermis, dermis, and subcutaneous tissue. Discussion of keratin, melanin, and conditions like albinism and vitiligo.