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The Integumentary System

Overview

  • Chapter discusses the integumentary system, which includes skin and its appendages.

Structure of the Skin

Major Regions

  • Epidermis: Outermost layer composed of keratinized stratified squamous epithelium.

  • Dermis: Middle layer containing two sub-layers.

    • Papillary Layer: Composed of areolar connective tissue with dermal papillae.

    • Reticular Layer: Main bulk of the dermis; dense irregular connective tissue.

  • Hypodermis (Superficial Fascia): Subcutaneous layer mainly made of adipose tissue.

Skin Appendages

  • Eccrine Sweat Gland: Maintains thermoregulation.

  • Sebaceous (Oil) Gland: Secretes sebum to lubricate skin.

  • Hair Follicles: Structure from which hair grows.

  • Hair Shaft and Root: Components of hair structure.

Functions of the Integumentary System

Protection

  • Chemical barriers: Low pH secretions and defensins inhibit bacterial growth.

  • Physical barriers: Keratin and glycolipids block water loss.

  • Biological barriers: Dendritic cells and macrophages improve immune response.

Body Temperature Regulation

  • Sweat glands help in regulating body temperature through evaporation.

Cutaneous Sensations

  • Includes sensations of temperature, touch, and pain.

Metabolic Functions

  • Vitamin D Synthesis: Involves conversion by skin cells.

  • Chemical Conversions: Involving carcinogens and hormones.

Blood Reservoir

  • Skin can hold approximately 5% of the body's blood volume.

Excretion

  • Nitrogenous wastes and salts are excreted through sweat.

Epidermal Layers

Stratum Corneum

  • Outermost layer; made of dead, keratinized cells.

Stratum Granulosum

  • Layer with flattened cells that contribute to waterproofing.

Stratum Spinosum

  • Layer providing skin strength and flexibility.

Stratum Basale

  • Deepest layer with actively dividing cells; site of keratinocyte formation.

Types of Skin Pigments

  • Melanin: Responsible for color; higher concentrations in darker skin.

  • Carotene: Presents in palms and soles.

  • Hemoglobin: Gives skin its pinkish hue.

Skin Cancer Types

Basal Cell Carcinoma

  • Most common type; arises from the stratum basale.

Squamous Cell Carcinoma

  • Second most common; involves keratinocytes of stratum spinosum.

Melanoma

  • Most dangerous; arises from melanocytes; highly metastatic.

    • ABCDE Rule for melanoma detection: Asymmetry, Border, Color, Diameter, Elevation.

Burns Classification

Partial-Thickness Burns

  • First Degree: Affects only the epidermis; reddening of the skin.

  • Second Degree: Affects epidermis and upper dermis; blisters form.

Full-Thickness Burns

  • Third Degree: Destroys entire skin thickness; skin grafting may be necessary.

Rule of Nines

  • Used to assess fluid loss in burns:

    • Head and neck: 9%

    • Upper limbs: 18%

    • Lower limbs: 36%

    • Trunk: 36%

    • Perineum: 1%