Integumentary System Review

Integumentary System Overview

• Skin: Largest organ, primary function is to protect the body.

  • Other functions include regulating temperature, producing vitamin D, immune surveillance, and sensory perception.

• Cells of the Skin:

  • Epidermis Cells:

  • Keratinocytes: Primary skin cells responsible for barrier formation.

  • Melanocytes: Pigment-producing cells that synthesize melanin, which gives color to the skin.

  • Langerhans Cells: Immune cells that carry antigens from skin to dermis, important for adaptive immune responses (e.g., against allergens).

  • Merkel Cells: Less understood role; associated with touch sensation.

  • Dermis Cells:

  • Mast Cells: Play a role in allergic responses.

  • Vascular Smooth Muscle Cells: Control blood vessel contraction and dilation to regulate temperature.

  • Fibroblasts: Produce and deposit collagen.

  • Immune Cells: Including lymphocytes, tissue macrophages, leukocytes that aid in healing and infection control (e.g., neutrophils).

  • Subcutaneous Cells:

  • Adipocytes: Fat cells organized in lobules, separated by septae (can lead to cellulite).

• Layers of the Skin:

  • Epidermis: Outer layer; composed mainly of keratinocytes. Continually sheds superficial layer.
  • Dermis: Deeper layer; contains connective tissue, hair follicles, sweat glands, blood vessels, nerves, and lymphatic vessels.
  • Subcutaneous Layer: Composed of fat cells and connective tissue.

• Dermal Appendages: Include nails, hair, sebaceous glands (secrete sebum), eccrine and apocrine sweat glands.

• Blood Supply and Innervation:

  • Rich supply through papillary capillaries.
  • Regulated by the sympathetic nervous system; involves vasoconstriction and vasodilation through alpha-adrenergic receptors.

Aging Changes in the Skin

• Reflect genetic and environmental factors:
  • Thinning, dryness, wrinkling, and pigmentation changes occur.
  • Reduction in the number of capillary loops, melanocytes, Langerhans cells.
  • Glands (sebaceous, eccrine, apocrine) atrophy affecting temperature regulation.
  • Decrease in sensory receptors, leading to reduced sensory perception.
  • Overall protective functions decline, increasing infection risk and delaying wound healing.

Skin Lesions

• Primary Lesions:

  • Macule: Flat change in color <1 cm.
  • Papule: Elevated, firm area <1 cm.
  • Patch: Flat macule >1 cm.
  • Plaque: Elevated, rough lesion >1 cm.
  • Wheal: Elevated, irregular edema, transient.
  • Nodule: Elevated, firm lesion 1-2 cm, deeper than papule.
  • Tumor: Solid lesion >2 cm, deeper in dermis.
  • Vesicle: Elevated, filled with serous fluid <1 cm.
  • Bulla: Vesicle >1 cm.
  • Pustule: Elevated, filled with purulent fluid, like a vesicle.
  • Cyst: Encapsulated lesion in dermis/subcutaneous layer filled with liquid/semisolid material.
  • Telangiectasia: Irregular red lines from capillary dilation.

• Secondary Lesions:

  • Scale: Flaky skin, keratinized cells.
  • Lichenification: Rough, thickened epidermis from chronic irritation.
  • Keloid: Elevated scar beyond wound boundaries.
  • Scar: Fibrous tissue replacing normal skin after injury.
  • Excoriation: Loss of epidermis, linear and crusted.
  • Fissure: Linear crack from epidermis to dermis.
  • Erosion: Loss of part of epidermis, depressed and moist.
  • Ulcer: Loss of epidermis and dermis, concave.
  • Atrophy: Thinning of skin surface.

Pressure Ulcers

• Result from unrelieved pressure, causing tissue damage.

  • Factors include shearing, friction, and moisture affecting capillary blood flow leading to ischemia.

• Stages of Pressure Ulcers:

  • Stage 1: Non-blanchable erythema of intact skin.
  • Stage 2: Partial-thickness skin loss involving epidermis or dermis.
  • Stage 3: Full-thickness skin loss involving subcutaneous tissue.
  • Stage 4: Full-thickness skin loss with damage to muscle, bone, or supporting structures.

Dermatitis Types

• Contact Dermatitis:

  • Allergic: T-cell mediated (Type IV) hypersensitivity; exposure leads to pruritus, vesicular lesions.
  • Irritant: Nonimmunologic inflammation from chemical irritation.

• Atopic Dermatitis: Common in childhood, chronic with family history of allergies.

• Seborrheic Dermatitis: Chronic inflammation, 'cradle cap' in infants.

Psoriasis vs Pityriasis

• Psoriasis: Chronic autoimmune skin disorder, produces thick, silvery lesions, often on scalp/elbows/knees.

  • Epidermal turnover significantly accelerated.
  • Types include plaque, inverse, guttate, pustular, erythrodermic.

• Pityriasis Rosea: Self-limiting, associated with viral infection, presents with herald patch.

Acne Basics

• Acne Vulgaris: Inflammatory pilosebaceous follicle disease, common in adolescence.
• Acne Rosacea: Inflammation of skin in middle-aged adults, characterized by flushing and sun sensitivity.

Lupus Erythematosus

• An autoimmune condition with skin manifestations; can be discoid (cutaneous) or systemic.
• Discoid lupus presents with a butterfly rash over the face; involves T and B cell dysregulation.

Vesiculobullous Disorders

• Pemphigus: Rare autoimmune disease leading to blister formation in the epidermis.
• Erythema Multiforme: Acute disorder causing target lesions.
  • Severe forms include Stevens-Johnson syndrome: severe blistering and necrosis.

Infections

• Bacterial:
  • Folliculitis: Infection of hair follicles; caused by Staphylococcus aureus.
  • Furuncles: Inflammation leading to boils, also caused by Staphylococcus aureus.
  • Cellulitis: Infection of dermis, commonly due to staphylococcus or streptococci.
• Viral:
  • Herpes Simplex Virus (HSV): Type 1 causes cold sores; Type 2 causes genital infections.

Fungal Infections

• Dermatophytes: Cause superficial skin infections (tinea).
  • Examples include tinea capitis (scalp), tinea pedis (athlete's foot).
• Candidiasis: Caused by Candida albicans, opportunistic under certain conditions.

Cold Injuries

• Result from exposure to extreme cold, leading to inflammation.
• Manifestations: skin appears white/yellowish and firm.

Burns

• Classified as partial-thickness or full-thickness injuries.
• Rules for burn assessment include total body surface area (TBSA) affected.
• Burn shock occurs after major injuries, leading to hypovolemia and multiple system effects.