Lecture 5 Slide Deck

Chapter 6 - The Integumentary System Lecture 5

Overview of Integumentary System

  • Integument means "covering"

  • Serves as a barrier from the outside world

  • Acts as the first line of defense

  • Composed of skin and its derivatives: hair, nails, glands

  • Contains all four primary tissue types (epithelial, connective, muscle, and nervous)

  • Large organ system that covers the entire body and accounts for approximately 8% of body weight

Functions of the Integumentary System

  • Protection/Barriers Against:

    • Abrasion

    • Microbes

    • Some chemicals

    • Fluid loss/gain

  • Thermoregulation:

    • Managed by blood vessels and sweat glands

  • Melanin Production:

    • Protects against UV radiation which may damage DNA

  • Lipid Storage:

    • Occurs in hypodermis

  • Vitamin D3 Production:

    • Vital for calcium absorption and reabsorption

  • Sensory Reception:

    • Relates to the nervous system

  • Electrolyte Homeostasis:

    • Excretion of nitrogenous wastes

  • Nonverbal Communication:

    • Skin plays a role in expressing emotions via facial muscles

Primary Components of the Integument

  1. Epidermis

    • Made of epithelial tissue

    • Nails represent scale-like modifications of the epidermis

  2. Dermis

    • Composed of connective tissues

    • Contains accessory structures (hair follicles, glands)

    • Houses blood vessels, nerves, and smooth muscle

  3. Hypodermis (Subcutaneous layer)

    • Not part of the integumentary system but influences it

    • Composed of areolar and adipose connective tissues

Epidermis Overview

  • Type of Tissue: Epithelial

  • Composed of five types of cells spread across four to five strata (layers)

    • Thick skin:

      • Found in palms, fingertips, bottoms of feet

      • Contains five strata and sweat glands

    • Thin skin:

      • Covers the rest of the body

      • Contains four strata with hair and sebaceous glands

  • Cell types in the Epidermis:

    1. Stem Cells - Located near the basement membrane; undergo mitosis

    2. Keratinocytes - Most common; produce keratin for protection

    3. Melanocytes - Produce melanin, located in stratum basale

    4. Tactile (Merkel) Cells - Touch receptors in stratum basale

    5. Dendritic (Langerhans) Cells - Immune response and pathogen defense

Epidermal Strata - Detailed Functions

  1. Stratum Basale:

    • Deepest layer; primarily stem cells

    • Melanocytes and tactile cells also found here

  2. Stratum Spinosum:

    • Second layer; 8-10 layers of keratinocytes o - Flattened as they move toward the apical surface

  3. Stratum Granulosum:

    • 3-5 layers where keratinization begins

    • Cells produce keratin and lipids for waterproofing

  4. Stratum Lucidum:

    • Clear layer in thick skin

    • Contains dead keratinocytes filled with eleidin

  5. Stratum Corneum:

    • Up to 30 layers thick; provides the outer layer of protection

    • Cells are dead and filled with keratin; sheds over time

Dermis Structure

  • Located below the epidermis

  • Composed of two layers:

    1. Papillary Layer:

      • 20% of dermis, made of areolar tissue

      • Contains dermal papillae which are involved in sensory reception

    2. Reticular Layer:

      • Deeper layer containing dense connective tissues

Hypodermis

  • Also referred to as subcutaneous layer or superficial fascia

  • Located beneath the dermis and above skeletal muscle

  • Functions include padding, insulation, and energy storage

Skin Color Determinants

  • Melanin: Produced from tyrosine by melanocytes; accounts for skin color variation

    • Types: Eumelanin (brown-black) and pheomelanin (red-yellow)

  • Effects of UV Radiation: Stimulates melanin production

  • Other pigments affecting color:

    • Hemoglobin: Imparts reddish/pinkish hue due to proximity of capillaries

    • Carotene: Orange pigment from vegetables; can alter skin tone

    • Jaundice: Yellowing from bilirubin buildup; common in liver dysfunctions

    • Cyanosis: Bluish tint from oxygen deficiency

    • Erythema & Pallor: Represent reactions to various physiological states

    • Albinism: Genetic condition resulting in no melanin production, leading to pale skin and hair.