Barriers to infection Flashcards
What is barrier immunity?
The first line defence against pathogens. It can be a physical barrier or actively present through tears, saliva, mucus and antimicrobial peptides.
What effect does mucous have in immunity? What areas does it protect the most?
It prevents adherence to epithelial cells, whilst allowing the passage of molecules. Its viscosity traps bacteria which can be cleared by mucociliary escalator or peristalsis. The mucous contains antimicrobial peptides. Protects intestines and lungs.
How does skin play a role in immune barrier?
Skin is an effective barrier until compromised by damage e.g. burns, insect, disease.
What increases the susceptibility of lung infection?
Defect in mucous or in the cilia e.g. Kartangner’s primary ciliary dyskinaesia.
What is the consequence of recurrent or severe lung infections?
Causes scarring, dilatation and distortion of the bronchi which inhibits mucous clearance and further increases susceptibility.
Why doesn’t the oral cavity, oropharynx and upper oesophagus require mucus protection?
Lined with stratified squamous epithelium.
What is irrigation?
A natural process to inhibit infection through:
- Continuous flow of urine to prevent UTI
- Tears, urine, saliva, bile, pancreatic secretions, mucus, sebaceous secretions all protect the surfaces they flow over.
Why might a UTI occur?
Due to a blockage that affects the renal system and the urine becomes static.
Failure of vesicoureteral vlave to prevent reflux back into ureter can cause infection and renal failure.
What happens in the flow of the irrigation fluids becomes static?
Becomes a prime site for bacterial growth
What is the function of acid secretions?
To sterilise digested food in the stomach before entering the small intestine.
What is contained within tears that provides a barrier?
Lysosymes that are bactericidal
What does bile acid do?
Inhibits pathogenic growth
What is bacterial flora?
Non-invasive commensal bacteria that help to prevent infection from pathogenic bacteria through competition. Flora is present in the mouth, skin, large intestines.
What compromises flora?
Antibiotics and excess antiseptic solutions. It allows pathogenic bacteria to colonise.
