UNIT 3 EXAM STUDY GUIDE

Resident microorganism vs transient microorganism

Resident microbes permanently live on the body and benefit the host; transient microbes are temporary microbes that do not permanently colonize the body.

What makes an environment inhospitable to transient microbes?

Skin oils, acidic pH, immune defenses, competition from normal microbiota, temperature, enzymes, and lack of nutrients.

When do we acquire our microbiome?

At birth and shortly after through contact with the mother and environment.

What is an opportunistic pathogen?

A microbe that normally does not cause disease but can when the immune system is weakened or it enters a new body site.

What allows opportunistic infections to occur?

Weakened immunity, damaged tissues, disrupted microbiota, or unusual entry into body sites.

What are the 3 infectious reservoirs?

Humans, animals, and the environment.

What are the major portals of entry?

Respiratory tract, gastrointestinal tract, urogenital tract, skin, and parenteral route.

Most common portal of entry

Respiratory tract.

How do microbes stick to the body?

Adhesion molecules such as pili, fimbriae, and surface proteins bind to host cell receptors.

What prevents microbes from staying in the body?

Skin barrier, immune defenses, mucus, stomach acid, tears, and normal microbiota.

What are portals of exit?

Pathways pathogens leave the body such as respiratory droplets, feces, urine, blood, skin cells, saliva, and reproductive fluids.

Difference between a sign and symptom

A sign is objective and observable; a symptom is subjective and felt by the patient.

What are the 5 stages of disease?

Incubation, prodromal, illness, decline, convalescence.

What is incubation stage?

Time between infection and first symptoms.

What is prodromal stage?

Early mild symptoms like fatigue or discomfort.

What is illness stage?

Disease symptoms are most severe.

What is decline stage?

Symptoms decrease as immune system controls infection.

What is convalescence stage?

Recovery period where the body heals.

What are the 3 modes of transmission?

Contact transmission, vehicle transmission, and vector transmission.

Direct transmission

Physical contact between infected and susceptible person.

Indirect transmission

Transmission through contaminated objects or surfaces.

Droplet transmission

Large respiratory droplets spread through coughing or sneezing.

What is a fomite?

An inanimate object that carries pathogens such as doorknobs or phones.

Foodborne transmission

Pathogens spread through contaminated food.

Waterborne transmission

Pathogens spread through contaminated water.

Airborne transmission

Pathogens spread through small particles suspended in air.

Body fluid transmission

Pathogens spread through blood or other body fluids.

Biological vector

Vector where pathogen reproduces inside the vector.

Mechanical vector

Vector that only carries pathogen without reproduction.

Acute disease

Disease that develops rapidly and lasts a short time.

Chronic disease

Disease that develops slowly and lasts a long time.

Latent disease

Pathogen remains inactive before symptoms appear later.

Communicable disease

Disease that spreads from person to person.

Non-communicable disease

Disease that does not spread between individuals.

Contagious disease

Disease that spreads easily between individuals.

Epidemiology

The study of disease distribution and spread in populations.

Incidence

Number of new cases of disease in a population.

Prevalence

Total number of cases in a population at a given time.

Endemic

Disease consistently present in a population.

Sporadic

Disease that occurs occasionally.

Epidemic

Large increase of disease cases in a region.

Pandemic

Disease spread across the world.

Exogenous infection

Infection caused by microbes entering from outside the body.

Endogenous infection

Infection caused by microbes already in the body.

Species resistance

Natural resistance of certain species to particular diseases.

Innate immunity

Nonspecific defenses present at birth.

Adaptive immunity

Specific immunity developed after exposure to antigens.

First line of defense

Skin, mucous membranes, secretions, normal microbiota.

Second line of defense

Phagocytes, inflammation, fever, complement proteins, interferons, NK cells.

How skin prevents infection

Acts as a physical barrier and produces antimicrobial secretions.

Chemicals on skin preventing infection

Sebum, sweat, antimicrobial peptides, acidic pH.

How mucous membranes prevent infections

Mucus traps microbes and cilia move them away.

What enzyme in tears prevents infection

Lysozyme.

Why normal microbiota prevent infection

They compete with pathogens for nutrients and space.

Granulocytes

Neutrophils, eosinophils, basophils.

Agranulocytes

Monocytes and lymphocytes.

Steps of phagocytosis

Chemotaxis, adherence, ingestion, digestion, elimination.

What eosinophils target

Parasites and worms.

What are NK cells

Natural killer cells that destroy virus infected and cancer cells.

What are TLRs

Toll like receptors that recognize pathogen patterns.

What do TLRs bind to

Pathogen associated molecular patterns (PAMPs).

What do interferons stop

Viral replication.

3 complement activation pathways

Classical, lectin, alternative.

What does complement form at the end

Membrane attack complex (MAC).

How MAC kills cells

Creates pores in the cell membrane causing lysis.

Signs of inflammation

Redness, heat, swelling, pain.

What is diapedesis

Movement of white blood cells through blood vessel walls.

How fever helps infection

Slows microbial growth and enhances immune response.

What type of immunity are you born with?

Innate immunity; it is nonspecific and present at birth.

What type of immunity develops over your lifetime and is specific?

Adaptive immunity; it develops after exposure to pathogens or vaccines.

What is species resistance?

The natural resistance of certain species to particular diseases.

What is included in the 1st and 2nd lines of defense?

Skin, mucous membranes, chemical barriers, phagocytes, inflammation, fever, complement proteins, interferons; these are part of innate immunity.

Dendritic cells in skin

Immune cells that capture antigens and alert the immune system.

Defensins

Antimicrobial peptides that disrupt microbial cell membranes.

Lysozyme in sweat

Enzyme that breaks down bacterial cell walls.

Lactic acid and salt in sweat

Create acidic and salty environment that inhibits microbial growth.

Dermcidins

Antimicrobial peptides produced in sweat that kill bacteria.

Sebum

Oily secretion from sebaceous glands that lowers skin pH and inhibits microbes.

Lysozyme in tears

Breaks down bacterial cell walls and helps flush microbes from eyes.

How does normal microbiota aid defense?

They compete with pathogens for nutrients and space and produce antimicrobial substances.

How does urine aid defense?

It flushes microbes from the urinary tract and has acidic properties.

What is NOT included in the 2nd line of defense?

Antibodies and lymphocyte memory (these belong to adaptive immunity).

What are phagocytes?

Cells that engulf and digest pathogens.

What percentage of blood is plasma?

About 55%.

What makes up plasma?

Water, proteins, nutrients, hormones, gases, and wastes.

What is serum?

Plasma without clotting proteins.

What percentage of blood is formed elements?

About 45%.

Function of erythrocytes (red blood cells)

Transport oxygen and carbon dioxide.

Function of platelets

Blood clotting and wound repair.

Function of leukocytes (white blood cells)

Defense against infection.

Difference between granulocytes and agranulocytes

Granulocytes have visible cytoplasmic granules; agranulocytes do not.

Examples of granulocytes

Neutrophils, eosinophils, basophils.

Examples of agranulocytes

Lymphocytes and monocytes.

Basophils

Release histamine and are involved in inflammation and allergies.

Eosinophils

Attack parasites and are involved in allergic reactions.

Neutrophils

Most abundant white blood cells; primary phagocytes against bacteria.

Lymphocytes

Immune cells involved in adaptive immunity.

NK cells

Natural killer cells that destroy virus-infected or cancer cells.

Monocytes

Largest white blood cells; develop into macrophages in tissues.

Differential white blood cell count

A test measuring percentages of each type of white blood cell.