9. Lung Infection Flashcards
What are the defences of the lung?
Mechanical, local and systemic
Give examples of mechanical defence?
Pathogens sticking to mucus or the epithelium acting as a barrier
Give examples of local defences?
BALT - samples antigens and produces antibodies
Neutrophils - mobilise from the circulation
Antimicrobial substances in secretions
What are the cilia surrounded by?
Periciliary fluid - watery
What floats on top of the cilia?
Mucus - sticky gel like
What is the rate at which cilium beats at?
15 times a second
Describe the movement of the cilium?
The backwards and forwards movement is different. When moving forward the cilium engages the mucus when it is vertical. It is withdrawn in a curved fashion within the periciliary fluid back to the start
What part of the cilia engages with the mucus?
Little claws
What rhythm does the cilia beat in?
metachronal rhythm
What is the arrangement of microtubules in cilium?
9+2 pattern with the 9 microtubules pairs on the outside with dynein arms
What are the dynein arms for?
They have ATPase which provides energy to move the microtubules up and down each other. It makes the cilia bend
What is the function of the central tubule?
It used as an axis to move against
What can problems with the host defence systems be?
congenital or acquired
What are the two most common acquired defects of the mucociliary system?
Cigarette smoking
Viral infection
What cigarette smoke do to the mucociliary system?
It destroys the cilia - makes you more prone to infection. Tight junctions begin to fall apart
How long does it take for cilia to regrow, restoring the mucociliary system?
6 weeks
What are compound cilia?
Groups of cilia which are useless - no function. This occurs when cilia grows back abnormally
What is the risk being infected by a virus?
It puts you at risk from a bacterial infection as well
What could be the reason of an acute and overwhelming syndrome?
Very virulent bug or disorder of the host defence
What could be the reason for recurrent-acute, slow to resolve syndrome?
Bronchial, pneumonic or abnormalities in host defence
Define dextrocardia and what does it suggest?
It is an abnormality where the heart lies on the right side. Suggests some sort of ciliary abnormality
People born with cilia that do not work have a heart on a random side of the body. Why?
This is because the microtubules are used to guide cells around during embryological development. So if the microtubules didn’t guide the cardiac cells to the right place then the cilia which are made up of microtubules won’t work.
What structural defects will mean that the cilia doesn’t work?
1) No outer dynein arms
Dynein arm defects
How do you identify defective cilia?
1) Biopsies - use a microscope to look at beating
2) Biochemical marker - look for reduced levels of NO
What bacteria is the most common cause of bronchitis and sinusitis?
Haemophilus influenzae
How do bacteria attach to the epithelial surface?
With hair like fimbriae which act as anchors. They then divide and form a colony
How do bacteria avoid clearance from airways?
1) Exoproducts that impair mucociliary clearance - disorganise ciliary beat, damage epithelium
2) Enzymes - breakdown local immunoglobulins
3) Exoproducts - impair neutrophil, macrophage and lymphocyte function
4) Adherence - increased epithelial damage and tight junction separation
5) Avoid immune surveillance
What is pneumonia?
Inflammatory condition of the lung affecting primarily the alveoli. The alveoli can be filled with pus
List the clinical features of pneumonia
Cough, sputum, fever, dyspnoea, pleural pain, headache
Why is there stabbing pleuritic chest pain in pneumonia?
When inflammation starts to affect the pain fibres on the surface of the lung
What is the most common cause of bacterial pneumonia
Streptococcus pneumoniae
How does streptococcus pneumonia cause inflammation?
Produces pneumolycin which punches holes in cells killing them. Has a negatively charged polysaccharide capsule which makes it more virulent
Define gas trapping
Air trapped when airways have collapsed - results in high RV. This is caused by lost of elasticity in to the lungs
What kind phlegm do people with bronchiectasis have?
Greeny phlegm
What are typical bronchiectactic airways?
Damaged airways which have fallen apart and are much bigger than they should be
What is bronchiectasis
Bronchiectasis is a disease in which there is permanent enlargement of parts of the airways of the lung
How is excess phlegm removed in brochiectatic patients?
physiotheraphy
What does the removal of phlegm help with?
Reduction of inflammation because then the neutrophils dont have a stimulus to move in
List the causes of chronic bronchial sepsis?
1) Congenital
2) Mechanical obstruction
3) Inflammatory pneumonitis
4) Fibrosis
5) Postinfective
6) Immunological
7) Imparied mucocillary clearance
8) Immune deficiency
What is the cycle of chronic inflammation
Microbial infection -> inflammation -> tissue damage -> Impaired lung defences ->
More infection = more inflammation
What is damage caused by inflammation based upon?
Protease anti-protease balance
Give an example of an anti-protease?
Alpha 1 antitrypsin
What is function of an anti-protease?
They neutralise proteases preventing damage to the body
Describe what happens in chronic inflammation in terms of proteases and anti-proteases?
In chronic inflammation there are so many neutrophils so much protease is released that it overwhelms the anti-proteases. The free proteases then cause damage
What effect does protease have on the epithelium?
It breaks down the epithelial surface causing damage
What are the risks of have damaged areas of epithelium?
They become more susceptible to infection
How does bronchiectasis affect the bronchial wall?
Patients with bronchiectasis have chronic inflammation resulting in high levels of neutrophils which digest the elastin
What could be the reason for daily purulent sputum only temporarily responding to antibiotic?
Abnormality in host defenses
What are the common complaints for patients with bronchiectasis?
Daily sputum production
Recurrent respiratory infections
Breathlessness
Fatigue
