Chapter_5_Integumentary

The Integumentary System

Overview

• The integumentary system encompasses skin, accessory structures (hair, nails, glands), and sensory receptors.

Accessory Structures

• Skin Functions:

  • Connective tissue layers: arteries, veins, and nerves form the cutaneous plexus.

  • Accessory structures include: hair shafts, sweat glands, sebaceous glands, tactile and lamellated corpuscles.

Functions of the Skin

• Protection:

  • Stratified epidermis protects against abrasions.

  • Sweat and sebum provide defense against bacterial infections.

  • Keratin aids in waterproofing skin.

  • Melanin protects against UV radiation.

  • White blood cells in the dermis contribute to immunity.

• Temperature Regulation:

  • Sweat evaporates to cool down the body.

  • Blood vessels adjust through vasoconstriction and vasodilation to manage heat loss.

  • Arrector pili muscles create goosebumps.

• Sensation:

  • Nerve endings detect touch, temperature, and pain.

• Excretion:

  • Sweat eliminates salts, lactic acid, and urea.

• Synthesis of Vitamin D:

  • Essential for calcium absorption.

Skin Structure

• Layers of Skin:

  • Epidermis and Dermis:

    • The epidermis has no blood vessels.

    • The dermis provides strength due to collagen and elastin fibers.

  • Subcutaneous Layer:

    • Attaches skin to underlying muscles.

Cells of the Epidermis

• Keratinocytes:

  • Produce keratin for protection and a waterproof barrier.

• Melanocytes:

  • Produce melanin for skin color and UV absorption.

• Langerhans Cells:

  • From bone marrow, they are involved in immune responses.

• Merkel Cells:

  • Act as touch receptors.

Epidermal Layers (come let’s get sun burned)

• Stratum Corneum:

  • Top layer with dead keratinized cells preventing microbial penetration.

• Stratum Lucidum:

  • Present in thick skin areas, composed of dead keratinocytes.

• Stratum Granulosum:

  • 3-5 layers thick with keratin production.

• Stratum Spinosum:

  • Contains live keratinocytes and Langerhans cells for immunity.

• Stratum Basale:

  • Deepest layer with actively dividing cells, melanocytes, and Merkel cells.

Dermis Structure

• Papillary Region:

  • Areolar connective tissue with dermal papillae containing capillaries and sensory receptors (Meissner’s corpuscles).

• Reticular Region:

  • Dense connective tissue providing strength and housing glands and hair follicles.

Hypodermis

• Also known as the subcutaneous layer, it consists of adipose tissue that anchors the skin to underlying muscles.

Skin Color Determinants

1. Melanin:

   • Brown pigment produced by melanocytes;

   • Influenced by genetics and UV exposure.

2. Carotene:

   • Yellow pigment from fruits/vegetables;

   • Source of Vitamin A.

3. Hemoglobin:

   • Blood capillaries contribute a reddish hue.

Skin Color Conditions

• Jaundice: Yellow skin due to liver dysfunction.

• Cyanosis: Bluish color from oxygen deficiencies.

• Erythema: Redness from inflammation or allergic reactions.

• Albinism: Lack of melanin causing pale skin.

• Vitiligo: Loss of skin pigmentation leads to patchy skin.

Accessory Structures: Hair

• Hair Hair Follicle Components:

  • Shaft, root, medulla, cortex, and cuticle.

  • Hair follicle surrounds the hair root, bulbing at the base.

• Hair Growth Phases:

  1. Anagen: Growth phase.

  2. Catagen: Transition phase.

  3. Telogen: Resting phase.

Glands of the Skin

• Sebaceous Glands:

  • Produce sebum for hair and skin lubrication.

• Sweat Glands:

  • Regulate body temperature and eliminate wastes.

• Three Types of Sweat Glands:

  • Eccrine: Widely distributed, active post-birth, secretes sweat.

  • Apocrine: Limited distribution, active post-puberty, thicker secretion.

  • Ceruminous glands: are modified sweat glands located in the ear canal.

Nails

• Composed of keratinized epidermis with distinct parts including nail body, root, and lunula.

Skin Types

• Thick Skin:

  • 5 epidermal layers found in palms and soles; lacks sebaceous glands.

• Thin Skin:

  • 4 layers present in most body regions; contains sebaceous glands.

Skin Wound Healing

• Superficial Wounds: Faster healing through keratinocyte migration.

• Deep Wounds: Involves four phases: inflammatory, migratory, proliferative, and maturation phases.

Skin Conditions and Cancer

• Skin Burns: Classified into first, second, and third degree based on severity.

• Skin Cancer:

  • Common types: basal cell carcinoma (most common), squamous cell carcinoma, malignant melanoma (most aggressive).

  • Importance of early detection for treatment effectiveness.

Aging Effects on the Integumentary System

• Decreased fibroblast activity results in loss of elasticity.

• Immune response diminishes with aging.

• Loss of subcutaneous fat makes skin thinner.

• Reduced gland activity leads to skin drying and cracking.

• Melanin production decreases, causing uneven skin pigmentation.