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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%