Pneumonia pathophysiology: Difference between revisions
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* In addition to the effects on the lungs, many viruses affect other [[Organ (anatomy)|organ]]s and can lead to illness affecting many different bodily functions. | * In addition to the effects on the lungs, many viruses affect other [[Organ (anatomy)|organ]]s and can lead to illness affecting many different bodily functions. | ||
* Viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral CAP. | * Viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral CAP. | ||
=== | ===Bacteria=== | ||
* Bacteria and fungi also typically enter the lung with inhalation, though they can reach the lung through the bloodstream if other parts of the body are infected. | * Bacteria and fungi also typically enter the lung with inhalation, though they can reach the lung through the bloodstream if other parts of the body are infected. | ||
* Often, bacteria live in parts of the [[upper respiratory tract]] and are constantly being inhaled into the alveoli. | * Often, bacteria live in parts of the [[upper respiratory tract]] and are constantly being inhaled into the alveoli. | ||
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* This results in the fever, chills, and fatigue common in CAP. The neutrophils, bacteria, and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. | * This results in the fever, chills, and fatigue common in CAP. The neutrophils, bacteria, and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. | ||
* Bacteria often travel from the lung into the blood stream and can result in serious illness such as [[septic shock]], in which there is low blood pressure leading to damage in multiple parts of the body including the [[brain]], [[kidney]], and [[heart]]. | * Bacteria often travel from the lung into the blood stream and can result in serious illness such as [[septic shock]], in which there is low blood pressure leading to damage in multiple parts of the body including the [[brain]], [[kidney]], and [[heart]]. | ||
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==Pathophysiology fungi== | ==Pathophysiology fungi== | ||
Fungi typically enter the lung with inhalation of their spores, though they can reach the lung through the bloodstream if other parts of the body are infected. Also, fungal pneumonia can be caused by reactivation of a latent infection. Once inside the alveoli, fungi travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune system to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system. This results in the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. | Fungi typically enter the lung with inhalation of their spores, though they can reach the lung through the bloodstream if other parts of the body are infected. Also, fungal pneumonia can be caused by reactivation of a latent infection. Once inside the alveoli, fungi travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune system to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system. This results in the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. | ||
Revision as of 18:46, 7 September 2012
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Pneumonia Microchapters |
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Diagnosis |
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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Philip Marcus, M.D., M.P.H.[2]
Overview
Bacteria and fungi typically enter the lung with inhalation. Once inside the alveoli, these microbes travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune system response by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs resulting in manifestations of pneumonia.
Pathophysiology
Microscopic Pathology
Viruses
- Viruses must invade cells in order to reproduce.
- Typically, a virus will reach the lungs by traveling in droplets through the mouth and nose with inhalation.
- There, the virus invades the cells lining the airways and the alveoli.
- This invasion often leads cell death either through direct killing by the virus or by self-destruction through apoptosis.
- Further damage to the lungs occurs when the immune system responds to the infection. White blood cells, in particular lymphocytes, are responsible for activating a variety of chemicals (cytokines) which cause leaking of fluid into the alveoli.
- The combination of cellular destruction and fluid-filled alveoli interrupts the transportation of oxygen into the bloodstream.
- In addition to the effects on the lungs, many viruses affect other organs and can lead to illness affecting many different bodily functions.
- Viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral CAP.
Bacteria
- Bacteria and fungi also typically enter the lung with inhalation, though they can reach the lung through the bloodstream if other parts of the body are infected.
- Often, bacteria live in parts of the upper respiratory tract and are constantly being inhaled into the alveoli.
- Once inside the alveoli, bacteria and fungi travel into the spaces between the cells and also between adjacent alveoli through connecting pores.
- This invasion triggers the immune system to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system.
- This results in the fever, chills, and fatigue common in CAP. The neutrophils, bacteria, and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation.
- Bacteria often travel from the lung into the blood stream and can result in serious illness such as septic shock, in which there is low blood pressure leading to damage in multiple parts of the body including the brain, kidney, and heart.
Pathophysiology fungi
Fungi typically enter the lung with inhalation of their spores, though they can reach the lung through the bloodstream if other parts of the body are infected. Also, fungal pneumonia can be caused by reactivation of a latent infection. Once inside the alveoli, fungi travel into the spaces between the cells and also between adjacent alveoli through connecting pores. This invasion triggers the immune system to respond by sending white blood cells responsible for attacking microorganisms (neutrophils) to the lungs. The neutrophils engulf and kill the offending organisms but also release cytokines which result in a general activation of the immune system. This results in the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation. Specific instances of fungal infections that can manifest with pulmonary involvement include:
- Pneumocystis jirovecii pneumonia
- Histoplasmosis, which has primary pulmonary lesions and hematogenous dissemination
- Coccidioidomycosis, which begins with an often self-limited respiratory infection (also called "Valley fever" or "San Joaquin fever")
- Pulmonary blastomycosis
- Sporotrichosis - primarily a lymphocutaneous disease, but can involve the lungs as well
- Cryptococcosis - contracted through inhalation of soil contaminated with the yeast, it can manifest as a pulmonary infection and as a disseminated one
- Aspergillosis, resulting in invasive pulmonary aspergillosis
- rarely, Candidiasis has pulmonary manifestations in immunocompromised patients.
Parasites
- In general, these parasites enter the body through the skin or by being swallowed.
- Once inside the body, these parasites travel to the lungs, most often through the blood. There, a similar combination of cellular destruction and immune response causes disruption of oxygen transportation.
Aspiration pneumonia pathophysiology
The location is often gravity dependent, and depends on the patient position. Generally the right middle and lower lung lobes are the most common sites of infiltrate formation due to the larger caliber and more vertical orientation of the right mainstem bronchus.
Patients who aspirate while standing can have bilateral lower lung lobe infiltrates. The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position. Depending on the acidity of the aspirate, a chemical pneumonitis can develop, and bacterial pathogens (particularly anaerobic bacteria) may add to the inflammation.
Histopathological Findings in Aspiration Pneumonia
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Histopathological Findings
Lobar pneumonia
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Pneumocystis pneumonia
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Aspiration Pneumonia
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Aspiration pneumonia, infant
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Desquamative interstitial pneumonia
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Legionella pneumonia
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Measles pneumonia
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Abscess, bronchopneumonia
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