Integumentary - Part 1

Integumentary System Overview

• Comprises three main regions: epidermis (superficial), dermis (middle), and hypodermis (deepest/subcutaneous layer, composed mostly of adipose tissue).
• Epidermis contains layers, with stratum basale at the bottom (cell mitosis) and stratum corneum at the top (dead, shingle-like cells).

Epidermal Layers

• Stratum Spinosum: Contains keratinocytes connected by desmosomes.
• Stratum Granulosum: Keratinization process begins here.
• Stratum Lucidum: Present only in thick skin (palms and soles).

Skin Color Determinants

• Melanin: Yellow to black pigment produced by melanocytes; responsible for skin color variation and freckles.
• Carotene: Yellow-orange pigment prevalent in palms and soles.
• Hemoglobin: Contributes to the pinkish hue of fair skin.

Dermis Structure

• Composed of strong, flexible connective tissue containing fibroblasts, macrophages, and white blood cells.
• Divided into two layers:
  • Papillary Layer: Contains areolar connective tissue, blood vessels, capillary loops, and sensory receptors (Meissner’s corpuscles).
  • Reticular Layer: Accounts for ~80% of dermis thickness, composed of collagen and elastic fibers providing strength and resilience.

Appendages of the Skin

• Sweat Glands:
  • Eccrine (merocrine) glands: Found on palms and soles; primarily for thermoregulation.
  • Apocrine glands: Found in axillary and anogenital areas; associated with sexual scent.
• Sebaceous Glands: Produce sebum, an oily secretion that softens and protects skin and hair.
• Hair: Embedded in follicles, alerting body to insects and providing protection.

Hair and Nails

• Hair follicles consist of connective tissue sheath and epithelial root sheath.
• Nails: Epidermal modifications on distal surfaces of fingers and toes, involving keratin formation.

Functions of the Integumentary System

• Protection: Establishes chemical, physical, and biological barriers.
• Temperature regulation: Through perspiration and vasodilation.
• Sensory perception: Detects temperature, touch, and pain.
• Metabolic functions: Synthesis of Vitamin D and collagenase; conversion of toxins.
• Blood reservoir: Holds up to 5% of body's blood volume.
• Excretion: Expels waste (e.g., urea, salts) via sweat.

Skin Cancer Types

• Basal Cell Carcinoma: Most common, least malignant; arises from stratum basale, often curable.
• Squamous Cell Carcinoma: Second most common; affects keratinocytes, usually on areas with frequent sun exposure.
• Melanoma: Most dangerous, highly metastatic; adheres to ABCD rule for identification.

Burns Classification

• Partial-Thickness Burns:
  • First-degree: Epidermal damage; causes redness and pain.
  • Second-degree: Epidermal and upper dermal damage; characterized by blisters.
• Full-Thickness Burns:
  • Third-degree: Destroys entire thickness of skin; may not cause pain due to nerve destruction.

Burn Severity Criteria

• Critical if:

  • 25% body has second-degree burns.

  • 10% body has third-degree burns.

  • Face, hands, or feet have third-degree burns.

Skin Homeostatic Imbalances

• Common infections:
  • Athlete’s foot (fungal), boils (bacterial), cold sores (viral).
• Allergic reactions:
  • Contact dermatitis due to allergen exposure; psoriasis often precipitated by trauma or stress.