1.1 Defensive Barriers Flashcards
Routes of Infection
Horizontal Transmission:
- Direct Contact
- Aerosol
- Oro-faecal
- Vector Borne
Vertical Transmission:
- Direct Contact
Vertical Transmission
Viruses are transmitted from mothers to their offspring
Horizontal Transmission
Viruses are transmitted among individuals of the same generation
5 Defensive Barriers and Examples
Physical - Skin
Physiological - Mucous membrane
Biochemical - Gastric acid
Chemical - Lysozyme
Cellular - Macrophages
Adaptations of the Respiratory Tract
~ Conductive System: Nasal cavity→ Pharynx→ Larynx→ Trachea→ Bronchi
~ Transitional System: Bronchioles
~ Gas Exchange System: Alveoli
~ Alveolar Macrophages
~ Mucociliary Escalator
~ Mucous
Adaptations of Skin
Sebaceous Glands and Sebum
AMPs: Beta-defensins
Keratinocytes
Adaptations of the Alimentary Tract
Stomach - Sterilisation and digestion of food
Gut-associated lymphoid tissue - Factor for immune response
Specific mucosal protective antibody (IgA)
What happens when the mucociliary escalator is damaged?
Predisposes the respiratory tract to:
~ Virus infection
~ Trauma (dust)
~ Toxins (ammonia)
Alveolar Macrophages Function and Formation
Function:
Main defence against inhaled microbial pathogens and inanimate particles
Formation:
Derived from blood monocytes and interstitial macrophages
Properties of Mucous
Composed of: water, electrolytes, glycoproteins and lipids
Antimicrobial Compounds:
~ Transferrin
~ Lactoferrin
~ Lysozyme
Antibodies - IgA
Antioxidants
Sebaceous Glands and Sebum Properties
Chemical barrier
Water repellent
Contains fatty acids
Anti-microbial components
What are AMPs: Beta defensins
Small cationic peptides
Broad-spectrum anti-microbial properties
Disruption of microbial membrane and/or interference with cellular functions
What do Keratinocytes do?
Trigger inflammation
Produce cytokines (immunological hormones)
Produce chemokines (cell migration factors)
What ways are epithelial surfaces susceptible to damage?
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
Commensal bacteria
On surfaces
Provide protection by:
~ Preventing pathogenic organisms from colonising through competition for resources.
~ Produce secretions which make the surface environment unfavourable for colonisation.
Melanocytes
Provide the skin protection from UV damage.
Which immunoglobulin is found within mucous?
IgA
Defensive barriers in the alimentary tract: Oral cavity & Oesophagus
Enzymes, physical barrier of stratified epithelium
Defensive barriers in the alimentary tract: Stomach
Bactericidal HCl
Proteases
Mucous
Defensive barriers in the alimentary tract: Intestines
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
What are Langerhan cells?
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
What is sebum?
Oily substance containing lipids and fatty acids
Water repellent and maintains slightly acidic surface environment (pH=5.5) which impairs bacterial growth
What does the stomach secrete?
HCl
pepsin
mucous
regulatory peptides
What is the purpose of mucous in the stomach?
To prevent damage and autolysis of the stomach epithelium
Mucociliary Escalator
Cilia coated with mucous that traps and moves dust and foreign bodies out of the tract. Lines respiratory tract from nose to bronchi
