1.1 Defensive Barriers

Question 1

Routes of Infection

Answer 1

Horizontal Transmission:
- Direct Contact
- Aerosol
- Oro-faecal
- Vector Borne

Vertical Transmission:
- Direct Contact

Question 2

Vertical Transmission

Answer 2

Viruses are transmitted from mothers to their offspring

Question 3

Horizontal Transmission

Answer 3

Viruses are transmitted among individuals of the same generation

Question 4

5 Defensive Barriers and Examples

Answer 4

Physical - Skin

Physiological - Mucous membrane

Biochemical - Gastric acid

Chemical - Lysozyme

Cellular - Macrophages

Question 5

Adaptations of the Respiratory Tract

Answer 5

~ Conductive System: Nasal cavity→ Pharynx→ Larynx→ Trachea→ Bronchi

~ Transitional System: Bronchioles

~ Gas Exchange System: Alveoli

~ Alveolar Macrophages

~ Mucociliary Escalator

~ Mucous

Question 6

Adaptations of Skin

Answer 6

Sebaceous Glands and Sebum

AMPs: Beta-defensins

Keratinocytes

Question 7

Adaptations of the Alimentary Tract

Answer 7

Stomach - Sterilisation and digestion of food

Gut-associated lymphoid tissue - Factor for immune response

Specific mucosal protective antibody (IgA)

Question 8

What happens when the mucociliary escalator is damaged?

Answer 8

Predisposes the respiratory tract to:
~ Virus infection
~ Trauma (dust)
~ Toxins (ammonia)

Question 9

Alveolar Macrophages Function and Formation

Answer 9

Function:
Main defence against inhaled microbial pathogens and inanimate particles

Formation:
Derived from blood monocytes and interstitial macrophages

Question 10

Properties of Mucous

Answer 10

Composed of: water, electrolytes, glycoproteins and lipids

Antimicrobial Compounds:
~ Transferrin
~ Lactoferrin
~ Lysozyme

Antibodies - IgA

Antioxidants

Question 11

Sebaceous Glands and Sebum Properties

Answer 11

Chemical barrier

Water repellent

Contains fatty acids

Anti-microbial components

Question 12

What are AMPs: Beta defensins

Answer 12

Small cationic peptides

Broad-spectrum anti-microbial properties

Disruption of microbial membrane and/or interference with cellular functions

Question 13

What do Keratinocytes do?

Answer 13

Trigger inflammation

Produce cytokines (immunological hormones)

Produce chemokines (cell migration factors)

Question 14

What ways are epithelial surfaces susceptible to damage?

Answer 14

External surfaces are susceptible to trauma and infection

Mucous membranes are susceptible as they are thin walled

Barriers can be defective (endogenous factors) or breached (exogenous factors), leading to disease

Question 15

Commensal bacteria

Answer 15

On surfaces

Provide protection by:
~ Preventing pathogenic organisms from colonising through competition for resources.
~ Produce secretions which make the surface environment unfavourable for colonisation.

Question 16

Melanocytes

Answer 16

Provide the skin protection from UV damage.

Question 17

Which immunoglobulin is found within mucous?

Answer 17

IgA

Question 18

Defensive barriers in the alimentary tract: Oral cavity & Oesophagus

Answer 18

Enzymes, physical barrier of stratified epithelium

Question 19

Defensive barriers in the alimentary tract: Stomach

Answer 19

Bactericidal HCl

Proteases

Mucous

Question 20

Defensive barriers in the alimentary tract: Intestines

Answer 20

Cryptidines which are toxic to bacteria

Peyer’s Patches: small mass of lymphatic tissue within the ileum. Contain T cells, B-lymphocytes and macrophages.

B-lymphocytes produce IgA

Question 21

What are Langerhan cells?

Answer 21

Cells present in dermis that detect for the immune system

~ detect the presence of a pathogen
~ langerhan cells migrate to the nearest lymph node and activate white blood cells
~ white blood cells travel to area of infection

This process initiates inflammation of the infected area

Question 22

What is sebum?

Answer 22

Oily substance containing lipids and fatty acids

Water repellent and maintains slightly acidic surface environment (pH=5.5) which impairs bacterial growth

Question 23

What does the stomach secrete?

Answer 23

HCl
pepsin
mucous
regulatory peptides

Question 24

What is the purpose of mucous in the stomach?

Answer 24

To prevent damage and autolysis of the stomach epithelium

Question 25

Mucociliary Escalator

Answer 25

Cilia coated with mucous that traps and moves dust and foreign bodies out of the tract. Lines respiratory tract from nose to bronchi