Dominican University A&P 1 - Lesson 5 - The Integumentary System

Dominican University

  • Course: Anatomy & Physiology I (BI223 DA 3)

  • Instructor: Spendy Pierre-Louis, PT, DPT, GCS

Principles of Anatomy & Physiology

Overview of the Integumentary System

  • Components: Skin, hair, oil and sweat glands, nails, and sensory receptors.

  • Functions:

    • Maintains body temperature.

    • Converts inactive vitamin D to its active form.

    • Provides sensory information.

    • Maintains homeostasis in several ways.

Maintenance of Homeostasis

Contributions of the Integumentary System

  • General Functions:

    • Protects internal organs with barriers from environmental agents.

    • Regulates body temperature via sweat glands and blood vessels.

Contributions by Body Systems

  • Skeletal System: Skin activates vitamin D for calcium and phosphorus absorption to maintain bones.

  • Muscular System: Supplies calcium ions necessary for muscle contraction.

  • Nervous System: Provides input for touch, pressure, thermal, and pain sensations through skin nerve endings.

  • Endocrine System: Keratinocytes convert vitamin D to calcitriol, aiding calcium absorption.

  • Cardiovascular System: Regulates blood flow through dermal blood vessels.

  • Lymphoid System: Acts as the first line of defense, with dendritic cells and macrophages combating microbes.

  • Respiratory System: Nose hairs filter dust; skin pain receptors can influence breathing rate.

  • Digestive System: Activates vitamin D for nutrient absorption.

  • Urinary System: Excretes waste through sweat; kidney cells convert skin-derived vitamin D.

  • Reproductive System: Skin nerve endings respond to stimuli; mammary glands produce milk when stimulated.

Structure of the Skin

Layers of the Skin

  1. Epidermis - The outer layer.

  2. Dermis - Beneath the epidermis.

  3. Hypodermis - Also called subcutaneous layer; not a true skin layer; consists of areolar and adipose tissue.

Components of the Integumentary System

  • Epidermal Cell Types:

    • Keratinocytes: Most prevalent; protect and waterproof skin.

    • Melanocytes: Produce melanin; contribute to skin color.

    • Langerhans cells: Immune response participants.

    • Merkel cells: Touch sensation.

Epidermal Layers in Thin vs. Thick Skin

  • Thin Skin:

    • Locations: All body parts excluding palms and soles.

    • Has hair follicles and sebaceous glands.

    • Epidermal thickness: 0.10–0.15 mm.

  • Thick Skin:

    • Locations: Palms and soles.

    • Lacks hair follicles; more sweat glands.

    • Epidermal thickness: 0.6–4.5 mm.

Functions of Skin

  • Thermoregulation: Maintains body temperature.

  • Blood Reservoir: Holds 8-10% of blood flow.

  • Protection: Physically and chemically protects body.

  • Cutaneous Sensations: Provides sensory feedback.

  • Excretion and Absorption: Eliminates substances; absorbs certain materials.

  • Synthesis of Vitamin D: Activates vitamin D for calcium absorption.

Wound Healing Processes

Epidermal Wound Healing

  1. Division of Basal Cells: Cells migrate across the wound surface.

  2. Thickening of Epidermis: New keratinocytes form.

Deep Wound Healing

  1. Inflammatory Phase: Clot formation.

  2. Migratory Phase: Clot becomes a scab; cells migrate.

  3. Proliferative Phase: Growth beneath scab.

  4. Maturation Phase: Scab sloughs off; tissue remodels.

Aging and Skin Changes

  • Age-associated changes: Wrinkles, dehydration, reduced sweat production, loss of melanocytes, and brittle nails.

Clinical Connections

Skin Cancer

  • Predominantly caused by UV light exposure.

  • Types: Basal cell carcinoma, squamous cell carcinoma, malignant melanoma.

Burns

  • Classified: First-degree (sunburn), second-degree (blistering), third-degree (full thickness).

Pressure Ulcers

  • Increased risk with age; result from blood flow deficiency.