Integumentary System - Module 5

Overview of the Integumentary System

• The integumentary system is the largest organ system of the human body.

• It consists of the skin and its accessory organs:

  • Hair

  • Nails

  • Sweat glands (sudoriferous glands)

  • Sebaceous glands

  • Nerves

  • Subcutaneous tissue (hypodermis)

• Dermatology is the medical study of the skin and its accessory components.

• A dermatologist is a physician specializing in the field of dermatology.

• A Medical Assistant (MA) in a dermatology setting is responsible for assisting with procedures for diagnosing and treating skin disorders, ensuring patient privacy, and providing patient education.

Functions of the Integumentary System

• Protection:

  • The skin acts as a barrier protecting the body and internal organs from the external environment.

  • Unbroken skin is the first line of defense against bacteria and toxins.

  • Keratin: A protein in the outermost layer that provides a waterproof barrier, preventing fluid loss and excessive water absorption during swimming or bathing.

  • Melanin: A pigment that protects underlying tissues from damage caused by ultraviolet (UV) exposure.

  • Acidic oily secretions from sebaceous glands inhibit the growth of bacteria and other organisms.

• Sensory Reception:

  • Sensory receptors in the dermis detect sensations of heat, cold, pain, touch, and pressure.

  • Receptors relay info to the brain to minimize injury and can recognize different textures.

• Regulation of Body Temperature (Thermoregulation):

  • The body maintains a normal internal temperature of $37^\circ C$ ($98.6^\circ F$).

  • Negative Feedback Mechanisms:

    • Vasodilation: Blood vessels dilate to release heat when body temperature increases.

    • Vasoconstriction: Blood vessels constrict to conserve heat when body temperature decreases.

    • Sudoriferous Gland Activity: Sweat glands become active to cool the body via evaporation or inactive to conserve heat.

  • Adipose tissue in the subcutaneous layer serves as an insulator.

• Synthesis of Vitamin D:

  • Precursor molecules in the skin synthesize Vitamin D when exposed to ultraviolet (UV) light.

  • Vitamin D is essential for the small intestine to absorb calcium and phosphorus, which are necessary for bone metabolism and muscle function.

Anatomy of the Skin

• The skin is composed of three distinct layers:

• Epidermis:

  • The outermost, avascular layer.

  • The basal cell layer consists of keratinocytes (new skin cells).

  • As cells move toward the surface, they lose their nuclei, die, and become filled with keratin.

  • Contains melanocytes, which produce melanin for skin color and UV protection.

• Dermis:

  • The middle layer composed of thick connective tissue.

  • Contains Collagen: Prevents the skin from tearing.

  • Contains Elastin: Provides resilience and elasticity.

  • Houses blood vessels, lymph vessels, hair follicles, sebaceous glands, and sweat glands.

• Subcutaneous Layer (Hypodermis):

  • Located below the dermis.

  • Consists of fat cells (adipose tissue) that provide insulation and store reserve calories.

Skin Lesions

Physical changes in the skin caused by irritants or infection are classified as lesions. MAs must document drainage, pain, pruritus (itching), excoriation, anatomical location, color, elevation, and texture.

• Primary Lesions (Appear immediately on the skin):

  • Macule: Flat area of color change, non-palpable (e.g., freckles).

  • Papule: Solid elevation less than $1\,cm$ in diameter with distinct borders (e.g., small raised pimple).

  • Nodule: Firm, movable solid elevation $0.5-1\,cm$ in diameter; extends deeper into the dermis than a papule.

  • Vesicle: Small raised blister containing clear fluid (e.g., herpes virus infection).

  • Bulla: Large vesicle greater than $1\,cm$ in diameter (e.g., burn blisters).

  • Pustule: Vesicle containing white cellular debris (pus); can be sterile or infected (e.g., acne).

  • Tumor: Large solid mass, may be benign or malignant, firm or soft (e.g., squamous cell carcinoma).

  • Plaque: Solid, elevated, flat-top lesion with indistinct borders (e.g., psoriasis).

  • Wheal: Transient, raised, edematous, red, circumscribed swelling caused by fluid accumulation in the dermis (e.g., intradermal skin tests, hives).

• Secondary Lesions (Evolve from primary lesions or result from complications/manipulation):

  • Scales: Thin, flaking layers of epidermis (e.g., psoriasis).

  • Crusts: Dried exudate on the skin.

  • Fissures: Linear, wedge-shaped cracks extending into the dermis.

  • Ulcerations: Areas of tissue loss involving the epidermis and often the dermis.

  • Scars: Fibrous tissue formed due to excess collagen production after injury.

  • Atrophy: Loss of a portion of the skin.

Common Skin Infections

• Bacterial Infections:

  • Impetigo: Caused by Streptococcus or Staphylococcus aureus; highly contagious, common in children. Characterized by small vesicles and crusty lesions with honey-colored exudate, usually around the mouth and nose.

  • Cellulitis: Acute infection of the subcutaneous tissue manifesting as redness, tenderness, swelling, and warmth. Can progress from minor cuts and may require IV antibiotics and hospitalization.

• Viral Infections:

  • Warts: Small, raised growths caused by Human Papilloma Virus (HPV).

  • Cold Sores: Caused by Herpes Simplex Virus Type 1 (HSV-1); painful ulcers on lips or gumlines.

  • Shingles: Caused by Herpes Zoster virus; painful rashes that follow dermatomes on the trunk or face. Preventable by vaccines.

• Fungal Infections:

  • Fungi grow on keratinized tissues (skin, hair, nails). Lesions have distinct borders and are pruritic.

  • Tinea Pedis: Athlete's foot.

  • Tinea Cruris: Jock itch.

  • Tinea Corporis: Ringworm.

  • Treatments: Topical antifungals like clotrimazole, ketoconazole, econazole, or nystatin.

• Parasitic Infections:

  • Scabies: Caused by Sarcoptes scabiei; causes intense itching, body rash, and sensation of crawling.

  • Pediculosis: Caused by lice; treated with medicated shampoo and environmental prevention steps.

Inflammatory and Autoimmune Disorders

• Seborrheic Dermatitis: Affects sebaceous glands, altering sebum quality/quantity. Presents as dry or moist greasy scales and yellowish crusts. Called dandruff in adults and cradle cap in infants.

• Contact Dermatitis: Acute inflammation from irritants/allergens (latex, poison ivy, lotions). Symptoms include erythema (redness), edema, pruritus, and vesicles.

• Eczema: Inflammation with unknown pathogenesis, possibly linked to dry skin, food allergies (in children), or stress/temp extremes. Presents as vesicular rashes on the face, neck, elbows, and behind knees.

• Psoriasis: Chronic autoimmune disease with rapid cell maturation. Symptoms include discrete pink/red lesions covered with silvery scales. Treatments: UV light, coal tar, methotrexate, and biologics.

• Systemic Lupus Erythematosus (SLE): Chronic autoimmune inflammatory disorder affecting connective tissue, kidneys, joints, and muscles. Characterized by a "butterfly" rash across the cheeks and nose, alopecia, and photosensitivity.

Hot and Cold Injuries

• Cold Injuries:

  • Prolonged exposure causes vasoconstriction, cell death, and potentially gangrene/amputation.

  • Superficial Frostbite: Burning, tingling, numbness; skin appears white or grayish.

  • Deep Frostbite: Hard, mottled, blue/gray skin after thawing; blister formation.

• Hot Injuries (Burns):

  • The Rule of Nines: Assessment tool where major body sections are assigned multiples of nine to calculate the percentage of Total Body Surface Area (TBSA) burned.

  • Superficial (First-degree): Affects only epidermis; erythema and pain (e.g., minor sunburn). Desquamation occurs in $3-7$ days.

  • Partial-thickness (Second-degree): Damages epidermis and dermis; characterized by thick-walled blisters and subcutaneous edema. Healing takes $10-28$ days.

  • Full-thickness (Third-degree): Extends through all skin layers into subcutaneous tissue; surface appears white, brown, or black and leathery.

Skin Growths and Neoplasms

• Benign Tumors: Noncancerous, encapsulated (does not spread), symmetric, and regular borders.

• Malignant Tumors: Cancerous, showing local invasion, regional spread (lymph nodes), or distant metastasis.

  • Types: Basal Cell Carcinoma, Squamous Cell Carcinoma, Malignant Melanoma.

  • ABCDE Rule for Melanoma Examination:

    • A: Asymmetry (unequal halves)

    • B: Border (irregularity)

    • C: Color (different shades of tan, brown, black, white)

    • D: Diameter (greater than $6\,mm$)

    • E: Elevation (raised mole)

• Prevention: Avoid midday sun ($10\,a.m.$ to $4\,p.m.$); use sunscreen (minimum SPF 15) every two hours; wear protective clothing/hats; avoid tanning beds.

Allergy Testing Methods

• Percutaneous (Scratch) Test: Performed on the forearm or back (preferred in children). Skin is labeled/numbered, a drop of allergen is applied, and the skin is pricked. Reaction (wheal) occurs in $10-30$ minutes.

• Patch Test: Allergen-soaked patch is placed on the skin for $48$ hours. Detects delayed reactions in contact dermatitis. Patients must avoid bathing/sweating during the test.

• Intradermal Test: $0.1-0.2\,mL$ of extract is injected into the intradermal layer. Used for penicillin, insect venom, and PPD (tuberculosis) tests.

• Radioallergosorbent Test (RAST): Blood test measuring specific antibodies (IgE) when mixed with allergens in a lab. Useful for patients who cannot stop antihistamines or have severe skin disorders.

Tissue Sampling and Biopsies

• Excision Biopsy: Removal of the entire lesion.

• Punch Biopsy: Removal of a small central section of a lesion.

• Shave Biopsy: Cutting/shaving the lesion at the skin line using a scalpel.

Skin Appearance Modification

• Chemical Peel (Chemexfoliation): Application of topical agents like Tretinoin (Retin-A) at $0.05\%-0.1\%$ concentration to remove acne scars and fine wrinkles. Side effect: photophobia.

• Botox Injections: Neurotoxin from Clostridium botulinum injected to paralyze facial muscles and smooth wrinkles. Effects last $3-4$ months.

• Dermabrasion: Handheld dermabrader with wire brushes or abrasive disks mechanically evens skin layers to treat acne scars.

• Laser Resurfacing (Photothermolysis): Uses laser to treat fine lines, wrinkles, and tattoos. Requires eye protection for all personnel and the patient.