13. Integumentary System

Integumentary System Overview

Course: HUBS 1401 Human Bioscience

Instructors: Elaine N. Marieb, Suzanne M. Keller

Edition: Thirteenth Edition, Global Edition

Learning Outcomes

• List general functions of each membrane type: cutaneous, mucous, serous, synovial.

• Describe the structure and location of each membrane type in the body.

• Compare tissue makeup of major membrane types regarding their specific functions and locations.

• Identify skin structures: epidermis, dermis (papillary and reticular), hair & hair follicles, sebaceous glands, sweat glands, and their specific roles.

• Name epidermis layers including stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale, and describe their characteristics including cellular composition and functions.

• Discuss contributions of epithelial, connective, muscle, and nervous tissues related to the integumentary system, emphasizing their interdependence and functionality.

Membranes

Definition:

Membranes are thin layers of tissue that line or cover body surfaces, playing vital roles in protection, absorption, and secretion.

Composition:

Most membranes consist of epithelial tissue supported by underlying connective tissue, facilitating both structure and function.

Types of Membranes:

1. Mucous membranes:

   • Line body cavities that open directly to the exterior, such as the respiratory, digestive, and urogenital tracts; they produce mucus to trap pathogens and keep surfaces moist.

2. Serous membranes:

   • Line body cavities that are closed to the exterior and cover the organs within these cavities (e.g., pleura, peritoneum). They secrete serous fluid to reduce friction between moving organs.

3. Cutaneous membrane (skin):

   • The largest organ of the body, covering and protecting internal structures.

4. Synovial membranes:

   • Line the joint cavities, providing lubrication to joints via the secretion of synovial fluid.

Epithelial Membranes

1. Cutaneous Membrane: Skin that provides a protective barrier covering the body surface.

2. Mucous Membranes: Line body cavities open to the exterior, such as the mouth and nasal passages, aiding in secretion and absorption.

3. Serous Membranes: Line body cavities closed to the exterior, serving as protective layers for organs within those cavities.

Connective Tissue Membrane

Components:

• Ligament: Connects bones to other bones at joints.

• Joint cavity: Contains synovial fluid, allowing smooth movement.

• Articular cartilage: Smooth, white tissue covering the ends of bones where they come together to form joints, aiding in shock absorption and smooth movement.

• Synovial membrane: Produces synovial fluid, ensuring joint lubrication and nourishment for cartilage.

Integumentary System Characteristics

Largest Organ System:

• Area: About 2m², varies by individual.

• Thickness: Ranges from approximately 0.5 to 4.0 mm, depending on the body location.

Functions:

• Provides a barrier against external environment: Protects from environmental hazards like UV radiation, pathogens, and physical injuries.

• Subject to mechanical, chemical, and biological attacks: The skin must respond and adapt to these threats.

Components of the Integumentary System

Division:

1. Cutaneous Membrane (Skin)

   • Epidermis: Outer layer of skin, providing protection.

   • Dermis: Beneath the epidermis, housing multiple structures.

2. Accessory Structures: Hair, nails, and glands (sebaceous and sweat).

Skin Structure

• Major layers:

  • Epidermis: Contains keratinocytes and provides protective functions.

  • Dermis: Layer rich in collagen and elastin, providing strength and elasticity.

  • Hypodermis (not part of the skin): Subcutaneous tissue that connects skin to underlying muscles, composed of loose connective and adipose tissues.

Additional Structures:

• Sensory receptors: Detect touch, pressure, and environmental changes.

• Arrector pili muscle: Causes hair to stand up, contributing to temperature regulation.

• Sebaceous gland: Produces sebum, moisturizing and protecting the skin.

• Sweat gland: Helps regulate body temperature and excretes waste.

• Adipose tissue: Provides insulation, energy storage and cushioning.

• Blood vessels: Supply nutrients and facilitate thermoregulation.

Functions of the Integumentary System

1. Protection: Acts as a barrier to external threats including mechanical, chemical, and biological.

2. Prevention of Dehydration: Reduces water loss through the skin.

3. Excretion: Removes waste products like water and salts.

4. Homeostasis: Regulates body temperature through methods such as vasodilation, insulation, and sweating for evaporative cooling.

5. Manufacture: Synthesizes Vitamin D when exposed to UV radiation, essential for calcium metabolism and bone health.

6. Sensation: Contains structures that detect touch, pressure, pain, temperature, providing critical environmental feedback for the body.

The Epidermis

Composition:

• Keratinized stratified squamous epithelium providing a tough barrier.

Layers:

• 4-5 layers of keratinocytes, each layer serving a unique function in skin protection, sensation, and absorption.

Epidermal Layers:

1. Stratum Basale:

   • Layer of cuboidal or columnar cells; contains stem cells for production of new keratinocytes.

2. Stratum Corneum:

   • The surface layer with 25-30 layers of flat, dead keratinocytes; constantly shed and replaced to maintain skin integrity.

Pigmentation of Skin:

• Influenced by several pigments which contribute to skin color and protection against UV radiation:

  • Carotene: Precursor to vitamin A, contributing orange and yellow hues.

  • Melanin: Produced by melanocytes in the stratum basale, transported to keratinocytes in melanosomes for pigment distribution.

The Dermis

Layers:

• Loose connective tissue: Provides flexibility and support.

• Dense irregular connective tissue: Gives skin its strength and resilience, containing ample collagen and elastic fibers, critical for skin elasticity and strength.

Hypodermis

Definition:

• The subcutaneous layer beneath the dermis, consisting primarily of loose areolar and adipose tissue.

Functions:

• Cushions and insulates the body; connects skin to underlying muscle and bone structures.

Burns Classification

Degree Types:

1. 1st Degree Burns: Affect only the epidermis, causing redness and minor pain.

2. 2nd Degree Burns: Affect both the epidermis and part of the dermis, resulting in blisters and more severe pain.

3. 3rd Degree Burns: Affect the entire thickness of the skin, appearing white or charred; often insensitive to pain due to nerve damage.

4. 4th Degree Burns: Extend into deeper tissues, potentially affecting muscles, tendons, and bones; characterized by severe damage and thick, leathery skin.

Hair and Nails

Hair:

• Covers most of the body; primarily protective against UV radiation, provides insulation, and offers sensory information through the hair follicle's nerve endings.

Nails:

• Composed of tightly packed, hard keratinized cells; functions to protect fingers/toes and enhance the precision of movements by aiding in grip and manipulation.

Summary

Membrane Types:

• Epithelial (cutaneous, mucous, serous) and Connective (synovial)

Integumentary System Composition:

• Comprises the cutaneous membrane and accessory structures like hair and nails, playing numerous protective and physiological roles in overall health and homeostasis.