Lung infection - sofia

Question 1

What are the three layers of the respiratory tract defence mechansim?

Answer 1

• mechanical: mucus, epithelium, cough, surfactant, cilia
• local: BALT, lysozymes, alveolar macrophages
• systemic: neutrophils, complement, immunoglobulins

Question 2

What is BALT?

Answer 2

Bronchus Associated Lymphoid Tissue - there is an immune system within the respiratory tract that samples antigens that your inhale and produces antibody to neutralise it.

Question 3

Mucociliary clearance: how much of the airway is lined by cilia, which type of junction join them, and which fluid surrounds the cilia?

Answer 3

The airways up to the respiratory bronchioles are lined by ciliated epithelia, joined by tight junctions. The cilia are surrounded by periciliary fluid which is watery. The mucus floats on top of the cilia and is more sticky and viscous.

Question 4

What is the pattern in which the cilia beat and the action of movement, and why?

Answer 4

If cilia beat forwards and then backwards along the same path, then if would just catch mucus on the way back and push mucus the wrong way. So the cilium backward movement is different to the forward movement . When it gets to the bottom of the forward stroke, the cilium is withdrawn in a curved fashion, within the periciliary fluid back to the start where the movement can repeat. The cilia have claws on their tips which engage with the mucus. The beating of cilia follows a metachronal rhythm.

Question 5

What is the ultrastructure of cilia?

Answer 5

There are 9 microtubule pairs arround 2 mircotubule pairs in the middle. Each microtubule pair in the outer circle has an inner and an outer arm (dynein arms). Microtubule pairs are joined by the nexin link. The inner 2 microtubules don’t have arms. Radial spokes join the outer microtubules to the inner, which is surrounded by radial spokes in a circle. The dynein arms have ATPase, which provides energy. The central microtubules are used as an axis to move against.

Question 6

What are the two main causes of host defence defects?

Answer 6

congenital or acquired

Question 7

What are the two most common causes of acquired of the mucociliary system defects?

Answer 7

• cigarette smoking: destroys cilia
• viral infection: destroys cilia and tight junctions fall apart. Person experiences cold like symptoms and their secretions are yellow-green. Whilst the cilia regrow the mucociliary system is disabled for 6 weeks.

Question 8

What happens when cilia grow back abnormally?

Answer 8

After damage, sometimes the cilia grow back abnormally. Groups of cilia joined are called compound cilia. They are useless.

Question 9

Respiratory Infection Syndromes - abnormal signs and what they could indicate

Answer 9

• Acute, Overwhelming: could be due to a very virulent bug, but could also be due to disorder of host defence
• Recurrent-acute, slow to resolve (with or without treatment): bronchial, pneumonic, abnormalities in host defences are present in people with recurrent acute illnesses
• Daily purulent sputum only temporarily responding to antibiotics:
  yellow/green phlegm on a daily basis is also unusual, could be an abnormality of host defences

Question 10

What is primary ciliary dyskinesia?

Answer 10

It is a genetic disorder causing defects in the cilia. This could be the lack of an outer dynein arm. This is a dynein arm defect, resulting in malfunctioning cilia.

Question 11

How are defective cilia identified?

Answer 11

• Biopsies are taken from the nose to look at under the microscope to see how the cilia are beating.
• Biochemical Marker: people with malfunctioning cilia do not have as much nitric oxide as normal people.

Question 12

What are some bacterial strategies to avoid being removed from the airways?

Answer 12

• making enzymes to break down immunoglobulins
• adherence, increased by epithelial damage and separating tight junctions
• exoproducts to impair WBC function
• exoproducts to impair mucociliary clearance e.g. disorganising cilia beating
• avoid immune surveillance e.g. by forming biofilm

Question 13

What are the clinical features of pneumonia?

Answer 13

• Cough
• Sputum
• Fever
• Dyspnoea
• Pleural Pain
• Headache

Question 14

What is the most common cause of pneumonia?

Answer 14

Streptococcus penumoniae - has a polysaccharide capsule around it. It is negatively charged, which makes it more difficult for the bug to bind to the epithelium but it also makes it much more virulent and able to invade the bloodstream and cause systemic infection. It produces a toxin called pneumolycin that punches holes in cells and kills them.

Question 15

How is pleural pain detected?

Answer 15

There are pain fibres on the surface of lungs, so when the lung becomes solid and the inflammation gets out to the periphery you get stabbing pleuritic chest pain

Question 16

Why do some people with diseased lungs have higher residual volumes that those with healthy lungs?

Answer 16

If your lung is diseased and has lost elasticity, as it collapses back down, the airways close down and air gets trapped.

Question 17

In a patient with pneumonia, a string of pearls is seen, what causes it?

Answer 17

Lots of dilated airways strung together by scar tissue. The whitening at the bottom of the dilations is the pooling of phlegm within the airways.

Question 18

What is bronchiectatic airways?

Answer 18

Some parts of the airways are permanently enlarged and so more mucus is present. The structure of the airways is damaged. People with bronchiectasis hoick up a lot of green phlegm.

Question 19

What are symptoms in people with bronchiectasis?

Answer 19

• Daily sputum production
• Recurrent respiratory infections
• Breathlessness : asthma and small airways disease
• Fatigue: severe tiredness and lethargy and difficulty in concentrating

Question 20

Why is getting rid of phlegm in patients with bronchiectasis important?

Answer 20

If you get rid of the dirty phlegm, you remove the stimulus for the neutrophils to move in and hence reduce the inflammation.

Question 21

What are some of the causes bronchiectasis?

Answer 21

• congenital: bronchial wall abnormalities
• mechanical obstruction: foreign body, tumour
• inflammatory pneumonitis: gastric contents
• fibrosis: CFA
• post-infective: TB, pneumonia
• immunological: post transplant
• impaired mucociliary clearance: CF
• immune deficiency: hypogammaglobulinaemia

Question 22

What is the vicious cycle of inflammation and infection?

Answer 22

If an infection becomes chronic, then you also get chronic inflammation, which can damage the body. Damage caused by inflammation further damages the lungs defences so you get more infection and more inflammation hence it is a vicious cycle.

Question 23

What is the main cause of the damage caused by inflammation, and how many inflammation damage the bronchi?

Answer 23

The damage caused by inflammation is largely due to the protease anti-protease balance. When a phagocyte phagocytoses the bacterium, it produces proteases that kill the bug. During phagocytosis, some of the protease spills into the surroundings. Normally there are anti-proteases in the airways to neutralise the protease enzyme. In chronic inflammation, there are so many phagocytes in the lungs and so much protease is released the antiproteases can’t cope. Hence more proteases are in the yellow-green sputum, which causes damage. The inflammation damages the bronchus itself - the constant traffic of neutrophils from the bloodstream to the airway lumen over a long period of time digests the structure of the bronchial wall and elastin.

Question 24

What is the most common anti-protease?

Answer 24

Alpha 1 anti trypsin

Question 25

What is the most common cause of bronchitis and sinusitis?

Answer 25

Haemophilus influenzae -
the bacteria have hair like fimbriae that act as anchors to get the bug to attach to the epithelial surface (bacteria stick down to damaged epithelium, not where there is cilia). Once on the epithelium, it begins to divide and form a colony.
Some bugs that are adapted to colonising the airways and aren’t as virulent.

Question 26

Why is the relationship between dextrocardia and ciliary abnormalities?

Answer 26

Dextrocardia (heart towards right) suggests that there could be some sort of ciliary abnormality (primary ciliary dyskinesia). In people born with cilia that doesn’t work, the side of the body that the heart is on is random. This happens because cilia guide cells around during embryological development.

Question 27

Why might the lung become solid during pneumonia?

Answer 27

The alveoli are full of pus.