lecture 5- pneumonias and acute lung injury Flashcards
What are the cells that make up the lining of the alveoli of the lungs?
There are the ciliated cells that transport mucous and the goblet cells that produce the mucous.
What are the two distinct cell types found within the alveoli and what are their roles?
Type 1 pneumocytes cover 95% of the alveolar surface. The type 2 alveolar cells produce surfactant, and are responsible for alveolar repair, including producing new type 1 cells where necessary.
What are the resident immune cells that can be found in the alveoli at any point in time?
There are resident macrophages, rare monocytes and white blood cells within the alveolar lining.
what is pneumonia?
Pneumonia is any respiratory disease that occurs from acute inflammation of the lung structures, such as the alveoli or bronchioles.
what are the two types of pneumonia one can contract?
Infectious pneumonia from bacterial, viral or fungal infections. Then there is non-infectious pneumonia, like inhalation or chemical peumonia.
what are the innate lung defenses that protect against pneumonia?
Innate defenses: mucous blanket, phagocytotic alveolar macrophages, phagocytotic recruited neutrophils, the complement system and draining lymph nodes.
what are the acquired lung defenses that protect against pneumonia?
Acquired defenses: antibodies IgA, IgG and IgM and T-cell accumulation from viral infections.
what causes pneumonia?
Failure of these lung defenses or a decrease in lung resistance can increase likelihood of getting pneumonia.
pneumonia likes what kind of health status in humans?
Pneumonia likes immunocompromised individuals, whose lung defenses are reduced.
what are the signs of acute pneumonia?
during acute pneumonia, the affected lung structure becomes inflammed, and filled with exudate fluid as a means of flushing out the pathogen. Lobar pneumonia refers to an entire lobe of the lung and broncho refers to the bronchioles spread randomly through the lungs.
Describe what happens 1-2 days into an acute inflammation of the lungs.
The lungs become heavy and full of blood (oedema).
describe what happens 2-4 days into an acute inflammation of the lungs.
This phase is called red hepatisation; in which the alveoli become filled with exudate rich in fibrin, red and white blood cells. The tissue is congested, and firm from oedema.
describe what happens 4-8 days into an acute inflammation of the lungs.
This phase is called grey hepatisation, because the red blood cells disintegrate leaving the alveoli filled with fibrin and neutrophils.
describe what happens 8 days or more into an acute inflammation of the lungs.
The immune system should have resolved the inflammation. The exudate should be drained and removed out of the lungs.
what are the complications of lobar pneumonia?
lung tissue destruction and necrosis (reduced functioning), spread of infection to the pleural cavity, spread of infection to other parts of the body causing acute inflammation in other visceral organs.
what are the symptoms of complication of lobar pneumonia?
malaise (general unwellness feeling), fever and chills, coughing, chest pain from pleural cavity infection, acute respiratory distress syndrome.
If two samples of lung tissue, one from a chronic and the other from acute inflammation, what would be the difference?
The chronic tissue sample would have more scarring and damage to lung parenchymal cells, granulomas would be present, whilst the acute tissue sample would have congested blood vessels and neutrophil infiltration
what is ARDS?
Acute Respiratory Distress Syndrome, is wide spread damage and destruction of the alveolar capillaries or epithelium or alveolar surfactant layer. It has a high mortality rate.
what can triggers ARDS in the lungs?
ionising radiation, near drowning, inhalation of hazardous chemicals, oxygen toxicity
Describe the first phase of ARDS.
The first phase of ARDS is the acute inflammation stage. The alveoli are filled with exudate, neutrophils, red blood cells, lymphocytes and macrophages. The type 1 alveolar cells begin to degenerate. By day 2, the type 1 alveolar cells die and are shed (sloughed). The type 2 alveolar cells proliferate to start the repair, and a hyaline cartilage membrane replaces the type 1 cells. Thrombi may start to form in the pulmonary arteries or in alveolar capillaries.
Describe the second phase of ARDS.
This is called the oxidative phase, and is much slower. Macrophages phagocytose the hyaline cartilage laid down and other debris in the alveoli and the type 2 cells begin to replace this with collagen (scarred tissue).
what are the possible outcomes of ARDS?
Complete resolution; the hyaline cartilage laid down and other debris may be cleared from the alveoli and replaced with new type 1 alveolar cells. Fibroblast proliferation ceases.
End-stage fibrosis; the collagen and hyaline cartilage laid down remains and so lung architecture is remodelled.
Fibrous tissue creates little spaces in the lung that can fill with fluid and form cysts. This is called ‘honeycomb lung’.
