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How the Body Prevents Infection

Unit 4 Lesson 2

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Describe the physical defenses against infection
Describe the chemical defenses against infection

Student Learning Outcomes

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Body Defenses

Two Main Types of Defenses

Specific Defenses

Immune system targeting specific pathogens
Example: white blood cells

Nonspecific Defenses

General barriers

Physical
Mechanical
Chemical barriers

Sandquist-Reuter, 2023

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Physical Defenses - The Skin

Three Layers of Skin

Epidermis

Top layer packed with keratin
Provides mechanical toughness
Acts as the first line of defense against microorganisms

Dermis

Middle layer containing connective tissue, hair follicles, and sweat glands
Provides strength and elasticity to the skin

Subcutaneous Tissue

Innermost layer composed of fat and connective tissue
Insulates the body and protects underlying muscles and bones

Sandquist-Reuter, 2023

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Physical Defenses - The Skin continued…

Risks of Broken Skin

Entry point for pathogens
Leads to potential infections
Importance of keeping skin moisturized and intact

Sandquist-Reuter, 2023

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Skin Layers

Sandquist-Reuter, 2023

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Physical Defenses - Mucous Membranes

Locations and Functions

Found in nose, mouth, lungs, urinary, and digestive tracts
Mucus

Moist, sticky substance trapping debris and microbes

Contains antimicrobial agents to neutralize pathogens

Mechanical Actions

Cilia Movement

Propels mucus out of respiratory tract

Sandquist-Reuter, 2023

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Physical Defenses - Mucous Membranes continued…

Risks

Smoking reduces cilia function
Aging weakens coughing
Increasing infection risk

Sandquist-Reuter, 2023

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Critical Thinking Question

The nurse’s aide is assisting a client who is bedridden and has a respiratory infection. The client frequently coughs and has difficulty expelling mucus.

How can the nurse’s aide help the client effectively manage and expel mucus to prevent further respiratory complications?

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Mechanical Defenses

Flushing Actions in the Body

Urine Flow

Removes microbes, maintaining urinary tract sterility

Tear Production

Blinking washes away debris from eyes

Additional Barriers

Eyelashes and Eyelids

Block dust and microorganisms from reaching eye surfaces

Sandquist-Reuter, 2023

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Eyelashes Are a Mechanical Defense Against Pathogens

Sandquist-Reuter, 2023

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Chemical Defenses - Skin and Sebum

Role of Sebum

Produced by sebaceous glands
Provides an oily barrier sealing hair follicles
Prevents bacteria from entering sweat glands and tissues

Environmental Influences

Low humidity can dry skin, increasing infection risk
Using moisturizers helps maintain skin's protective barrier

Sandquist-Reuter, 2023

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Critical Thinking Question

A client complains of dry, cracked skin on their hands. The nursing assistant is aware that this condition can increase the risk of infection. Which action would best support the client's skin integrity and reduce infection risk?

a) Encourage the client to wash hands frequently with hot water.

b) Apply a moisturizer after handwashing to maintain skin moisture.

c) Suggest avoiding handwashing to prevent further drying.

d) Use alcohol-based hand sanitizers exclusively to kill bacteria.

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Chemical Defenses - pH Levels and Enzymes

Urinary Tract

Slightly acidic urine inhibits pathogen growth

Respiratory Tract

Chemical mediators in nasal passages and lungs have antibacterial effects

Digestive Tract

Enzymes destroy microorganisms in stomach acid
Importance of hand hygiene to prevent fecal-oral transmission

Sandquist-Reuter, 2023

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Critical Thinking Question

The nurse’s aide is caring for a client with a urinary catheter. What practice is essential to support the urinary tract's natural defenses against infection in this scenario?

a) Maintain a closed drainage system to prevent contamination.

b) Limit fluid intake to reduce urine output and keep the catheter dry.

c) Frequently disconnect the catheter for cleaning.

d) Use antiseptic wipes every time you handle the catheter.

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Importance of Maintaining Defenses

Overall Health Impact

Strong defenses reduce infection risk
Lifestyle choices enhance defenses
Examples: Avoiding smoking, proper skin care, balanced nutrition

Practical Application

Regular hand washing
Maintaining skin integrity and moisture

Sandquist-Reuter, 2023

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Critical Thinking Question

A resident in a long-term care facility has been diagnosed with mild dehydration, leading to dry mucous membranes in the mouth and throat.

What interventions can the nursing assistant implement to support the client's mucous membranes and prevent infection?

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References

Sandquist-Reuter, M. (2023). Nursing Assistant. WisTech Open. https://wtcs.pressbooks.pub/nurseassist/

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