Chapter+6+PPT

Chapter Overview

• Title: Anatomy & Physiology: An Integrative Approach

• Authors: Michael P. McKinley, Valerie Dean O’Loughlin, Theresa Stouter Bidle

• Copyright: 2022 © McGraw Hill LLC

• Premise: Learning is foundational for understanding anatomy and physiology.

Integumentary System

• Definition: The largest system of the body, consisting of skin and accessory tissues.

• Weight: Accounts for approximately 16% of body weight.

• Components:

  • Cutaneous membrane (skin).

  • Accessory structures: hair, nails, sweat glands, sebaceous glands.

Major Parts of Integumentary System

• Cutaneous Membrane: The outer skin.

• Accessory Structures: Includes hair, nails, and various glands.

Composition and Functions of the Integument

Layers of the Integument

1. Epidermis:

   • Composed of stratified squamous epithelium.

2. Dermis:

   • Deeper layer made primarily of dense irregular connective tissue.

3. Subcutaneous Layer (Hypodermis):

   • Deep to the dermis, composed of areolar and adipose connective tissue; not part of the integumentary system.

Epidermis: Structure and Layers

• Epidermis Overview: Keratinized, stratified squamous epithelium consisting of multiple layers:

  • Stratum Basale: Deepest layer; forms a strong bond between epidermis and dermis. Contains keratinocytes, melanocytes, and tactile cells.

  • Stratum Spinosum: Comprises several layers of keratinocytes; includes dendritic cells that initiate the immune response.

  • Stratum Granulosum: Contains 3 to 5 layers; keratinization begins, cells become flattened and die.

  • Stratum Lucidum: Present only in thick skin areas (palms and soles); thin, translucent layer.

  • Stratum Corneum: Outermost layer; 20-30 layers of dead, keratinized cells, water-resistant and protective.

Keratinocytes and Melanocytes in Stratum Basale

• Keratinocytes:

  • Stem cells dividing to produce new cells; synthesize keratin.

• Melanocytes:

  • Responsible for producing melanin, which protects against UV radiation by transferring pigments into keratinocytes.

• Tactile Cells (Merkel Cells):

  • Assist in touch sensation, found in hairless skin areas.

Skin Color Variations

• Normal Skin Color:

  • Influenced by hemoglobin, melanin, and carotene.

• Melanin Variation:

  • Eumelanin (brown/black) and pheomelanin (tan/yellow).

• Conditions: Albinism results from lack of melanin production.

Skin Markings and Ablation

• Nevus (Mole): Overgrowth of melanocytes; monitored for changes in malignancy risk.

• Freckles: Localized increase in melanocyte activity.

• Friction Ridges: Unique patterns of dermis and epidermis; fingerprints.

Dermis Structure and Function

Layers of the Dermis

• Papillary Layer:

  • Composed of loose areolar connective tissue, contains dermal papillae interlocking with epidermal ridges.

• Reticular Layer:

  • Thicker, dense irregular connective tissue; provides strength, elasticity, and houses many skin structures (hair follicles, sweat glands).

Tension Lines

• Definition: Lines of cleavage formed by collagen and elastic fibers; important for surgical incisions to minimize scarring.

Subcutaneous Layer (Hypodermis)

• Composition:

  • Not part of the integument; consists of areolar and adipose tissue.

• Function:

  • Provides protection, energy storage, and insulation; common site for drug injections.

Functions of the Integument

1. Protection:

   • Shields against injury, harmful substances, and microbial infections.

2. Prevention of Water Loss:

   • Epidermis allows some water loss through sweating and transpiration.

3. Vitamin D Synthesis:

   • Process initiated in the skin, crucial for calcium and phosphate absorption.

4. Secretion/Absorption:

   • Secretes waste products via sweat; selectively absorbs certain chemicals.

5. Temperature Regulation:

   • Vasodilates or constricts to manage heat.

6. Sensory Reception:

   • Contains receptors for touch, pressure, and temperature.

Nails and Hair

Nails

• Structure:

  • Modifications of stratum corneum for protection and grasping.

• Components: Nail matrix, lunula, nail bed, cuticle, and hyponychium.

Hair

• Types:

  • Lanugo (fine, unpigmented), vellus (fine hair), and terminal hair (thicker, pigmented).

• Structure: Hair bulb, root, shaft, and follicle.

• Functions: Protection, sensory reception, and temperature regulation.

Skin Glands

Sweat Glands

1. Merocrine: Widely distributed; important for thermoregulation.

2. Apocrine: Found in specific areas; produce odor when decomposed by bacteria.

Sebaceous Glands

• Produce sebum, lubricates skin and hair, prevents bacterial growth.

Wound Healing

Stages

1. Bleeding and clot formation.

2. Granulation tissue formation; regeneration of blood vessels.

3. Epithelium regenerates; fibrosis occurs.

Aging and Skin Health

• Changes:

  • Reduced activity, thinner skin, loss of elasticity, and decreased immune response.

• Influences:

  • Extended UV exposure and smoking accelerate aging and increase skin cancer risk.