Chapter 4 - Skin and Body Membranes PowerPoint

Chapter 4: Skin and Body Membranes

Overview

• Introduction to body membranes and their significance

• Division into major categories to understand their structure and function

Body Membranes

Functions

• Cover body surfaces

• Line body cavities

• Form protective sheets around organs

• Classified based on tissue types

Major Categories

• Epithelial Membranes

  • Cutaneous membranes

  • Mucous membranes

  • Serous membranes

• Connective Tissue Membranes

  • Synovial membranes

Epithelial Membranes

General Information

• Simple organs also called covering and lining membranes

• Composed of both epithelial and connective tissue layers

Types of Epithelial Membranes

1. Cutaneous Membrane (Skin)

   • Dry membrane; outermost protective boundary

   • Composed of:

     • Epidermis: keratinized stratified squamous epithelium

     • Dermis: mostly dense, fibrous connective tissue

2. Mucous Membranes (Mucosae)

   • Moist membranes lining cavities open to exterior

   • Secretes protective mucus; adapted for absorption or secretion

   • Composed of:

     • Varies in epithelium type based on location

     • Loose connective tissue (lamina propria)

3. Serous Membranes (Serosae)

   • Line closed compartments in the ventral body cavity

   • Occur in pairs (visceral and parietal layers) with serous fluid in between

   • Composed of simple squamous epithelium and areolar connective tissue

   • Key examples:

     • Peritoneum: covers abdominal organs

     • Pleurae: surrounds lungs

     • Pericardia: surrounds the heart

Connective Tissue Membranes

• Synovial Membranes

  • Consist solely of loose areolar connective tissue

  • Lines fibrous capsules surrounding joints

  • Secretes lubricating fluid for cushioning and movement

Integumentary System

Components

• Skin (cutaneous membrane)

• Skin appendages:

  • Sweat glands

  • Oil glands

  • Hair

  • Nails

Functions of the Integumentary System

1. Insulation and cushioning of organs

2. Protection against:

   • Mechanical damage (bumps and cuts)

   • Chemical damage (acids and bases)

   • Thermal damage (heat or cold)

   • Ultraviolet radiation

   • Microbes (bacteria)

   • Water loss

3. Regulation of heat loss controlled by the nervous system

4. Mini-excretory system for waste removal (urea, salts, water)

5. Synthesis of vitamin D

6. Creation of a protective acid mantle via secretions

Detailed Function Breakdown (Table 4.1)

1. Mechanical Damage: Keratinized physical barrier with pain receptors

2. Chemical Damage: Keratinized layers and pain receptors protect against irritants

3. Microbial Damage: Unbroken surface plus acid mantle inhibit pathogen penetration

4. Ultraviolet Radiation: Melanin produced by melanocytes provides protective effect

5. Thermal Damage: Nerve receptors alert to temperature extremes

6. Heat Regulation: Can increase or decrease blood flow through capiliary beds

7. Waste Excretion: Via perspiration

8. Vitamin D Synthesis: From cholesterol compounds with sunlight exposure

Structure of the Skin

General Overview

• Made of two main tissue types: epidermis and dermis

• Subcutaneous tissue (hypodermis) beneath skin; anchors skin to organs (not part of integumentary system)

• Composed primarily of adipose tissue for shock absorption and insulation

Epidermis

1. Outer Layer: Stratified squamous epithelium

2. Keratinocytes: Produce keratin, which toughens the skin

3. Layer Composition:

   • Five strata: basale, spinosum, granulosum, lucidum (only in thick skin), corneum

Specific Stratum Details

• Stratum Basale: Deepest layer; cell proliferation

• Stratum Spinosum: Flatter, keratinized cells

• Stratum Granulosum: Contains dying cells; keratin production

• Stratum Lucidum: Present in thick skin only; high keratin content

• Stratum Corneum: Outermost layer; dead, keratin-filled cells prevent water loss

Key Epidermal Cells

• Melanin: Produced by melanocytes (color range yellow to brown to black)

• Epidermal Dendritic Cells: Immune response activation

• Merkel Cells: Touch perception

Dermis

• Comprised of connective tissue; divided into two regions:

  1. Papillary Layer: Upper layer with projections (dermal papillae) containing capillaries and receptors

  2. Reticular Layer: Deeper layer, providing structure with dense connective tissue and inclusions (glands, pressure receptors)

Skin Color

Influencing Pigments

1. Melanin: Yellow to black pigments

2. Carotene: Orange-yellow pigment [ also found in some vegetables]

3. Hemoglobin: Red pigment from blood cells

4. ctl ;blue pigment that can give skin a bluish tint, particularly in areas where blood vessels are close to the surface.

Abnormal Skin Colorations

• Erythema: Redness due to various factors (embarrassment, fever)

• Pallor: Blanching due to stress or poor circulation

• Jaundice: Yellowing indicating liver issues [ first nail bends and then the eyes}

• Bruises: Hematomas indicated by black/blue marks

Appendages of the Skin

Types of Glands

1. Sebaceous Glands: Produce sebum; provide moisture and antibacterial properties

2. Sweat Glands: Two types—eccrine and apocrine

   • Eccrine: Most numerous, regulate temperature through sweat acidic sweat

   • Apocrine: Found in certain body areas; become active at puberty

Hair Characteristics

• Composed of hard keratin; pigmentation from melanocytes

• Produced in hair follicles; growth occurs at the hair bulb in the stratum basale

• arrector pili muscle -

Nail Structure

• Heavily keratinized, protecting digits and providing function

• Growth occurs in the nail matrix; nails lack pigment

Homeostatic Imbalances of Skin

Common Infections and Disorders

1. Fungal Infections: Athlete’s foot [ tinea pedis]

2. Bacterial Infections: Boils, impetigo

3. Skin Conditions: Psoriasis

4. cold sores [ fever blisters] caused by HPV are viral infections that can cause painful sores on the lips and around the mouth, often triggered by stress or illness.

Burns Classification

• Severity influences treatment:

  • First-degree: Affects epidermis, red and swollen

  • Second-degree: Blistered, involves dermis, painful and red

  • Third-degree: Destroys dermis and epidermis burned area is painless [ gray black or white]

  • Fourth-degree: Extends to deeper tissues, requires surgical intervention [ may require amputation] appears dry

Skin Cancer Types

most common

1. Basal Cell Carcinoma: Least malignant [most common] appear shiny dome - shaped nodules

2. Squamous Cell Carcinoma: Can metastasize [uv exposure]

3. Malignant Melanoma: Most severe; detects using ABCDE rule [most deadly skin cancers]

Developmental Aspects of Skin

• Changes throughout life:

  • Lanugo covers fetuses; oily covering (vernix) at birth downy hair

  • Aging leads to thinner, less elastic skin; increased risk of cancer and hair loss

  • milia small white spots

  • in youth skin is thick and wall hydrated 

    blading and alopecia