Pathology of Respiratory System

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Questions and Answers

What is the primary cause of resorption atelectasis and how does it lead to alveolar collapse?

The primary cause of resorption atelectasis is obstruction of the bronchus by a mucus plug, leading to the gradual absorption of air from the distal airways and subsequent alveolar collapse.

Explain the relationship between chronic obstructive airway diseases (COPD) and the FEV1 : FVC ratio.

COPD is characterized by a marked decrease in FEV1 and either a normal or increased FVC, resulting in a decreased FEV1 : FVC ratio.

Describe the mechanism of contraction atelectasis and its impact on lung function.

Contraction atelectasis occurs due to fibrotic changes in the lung or pleura that impede lung expansion and increase elastic recoil during expiration.

Identify the role of surfactant in microatelectasis and its significance in respiratory distress syndrome.

Surfactant plays a crucial role in maintaining alveolar stability and preventing collapse; its loss in microatelectasis can lead to inadequate lung expansion in respiratory distress syndrome. Signup and view all the answers

What distinguishes atopic asthma from other types of asthma?

Atopic asthma is distinguished by its IgE-mediated hypersensitivity reaction, often triggered by environmental allergens. Signup and view all the answers

What initiates the triggering of mast cells in the mucosal surface, and what is a key mediator released?

The triggering of mast cells occurs in the mucosal surface, with histamine being a key mediator released. Signup and view all the answers

Identify two toxic proteins contained in eosinophils and their effects on epithelial cells.

Eosinophils contain major basic protein and eosinophilic cationic protein, both of which are directly toxic to epithelial cells. Signup and view all the answers

Describe the key morphological findings in the lungs of a patient with asthma.

Findings include overdistention of lungs with areas of atelectasis and occlusion of bronchi by thick tenacious mucus plugs. Signup and view all the answers

What are the main cellular components involved in the inflammatory infiltrate of asthma, and what percentage do eosinophils represent?

The main cellular components include eosinophils, mast cells, basophils, macrophages, and neutrophils, with eosinophils representing 5-50% of the infiltrate. Signup and view all the answers

What are the clinical features of an acute asthmatic attack, and how long can it last?

Clinical features include chest tightness, dyspnea, wheezing, and cough with or without sputum production, lasting up to several hours. Signup and view all the answers

Study Notes

Atelectasis

Defined as loss of lung volume due to inadequate expansion of airspaces.
Causes ventilation-perfusion imbalance, leading to hypoxia.
Types of Atelectasis:
- Resorption Atelectasis: Results from bronchial obstruction causing gradual air absorption and alveolar collapse; common causes include mucus plugs, tumors, foreign bodies, or enlarged lymph nodes.
- Compression Atelectasis: Arises from fluid, blood, or air accumulation in the pleural cavity that collapses adjacent lung; often associated with pleural effusions from congestive heart failure.
- Microatelectasis: Generalized loss of lung expansion primarily due to loss of surfactant, involved in adult and neonatal respiratory distress syndrome.
- Contraction Atelectasis: Caused by localized or generalized lung or pleura fibrosis that restricts lung expansion.

Chronic Obstructive Airway Diseases (COPD)

COPD encompasses airflow obstruction disorders, characterized by reduced FEV1 and a decreased FEV1/FVC ratio.
Includes conditions like asthma, emphysema, chronic bronchitis, and bronchiectasis.
Airway obstruction is caused by goblet cell hyperplasia, inflammatory edema, and muscle hypertrophy.

Asthma

Characterized by episodic, reversible bronchospasm due to exaggerated bronchoconstrictor responses.
Classification:
- Atopic Asthma: Most common type, involving IgE-mediated hypersensitivity.
- Mast Cell Role: Activation leads to bronchi contraction via mediator release (e.g., histamine, IL-4, leukotrienes).
- Eosinophil Role: Contains major basic protein and eosinophilic cationic protein, causing epithelial damage; active eosinophils produce various mediators.
Morphology:
- Gross: Overdistended lungs with occluded bronchi due to thick mucus plugs.
- Microscopic: Edema, hyperemia, increase in inflammatory infiltrate (eosinophils, mast cells, etc.), submucosal gland enlargement, and smooth muscle hypertrophy.

Clinical Features of Asthma

Symptoms include chest tightness, dyspnea, wheezing, and cough; acute attacks may last hours.
Long-term can progress to COPD, cor pulmonale, or respiratory epithelium dysplasia leading to cancer.

Chronic Bronchitis

Defined by mucus hypersecretion and airway obstruction, often due to long-standing inhaled irritants like tobacco smoke.
Characterized by enlarged mucous secreting glands in airways and an increase in goblet cells leading to excessive mucus.
Often results in recurrent infections and other complications like pulmonary hypertension.
Morphological findings include swollen, hyperemic airway lining covered in mucopurulent sputum and histological changes such as squamous metaplasia.

Clinical Features of Chronic Bronchitis

Persistent cough and sputum production; can progress to obesity and respiratory failure.
Complications include infections, pulmonary hypertension, and heart failure.

Bronchiectasis

Permanent dilation of bronchi/bronchioles due to destruction of muscle and elastic tissue, secondary to chronic infections or obstruction.
Associated with conditions like cystic fibrosis, immunodeficiencies, and post-infection states (e.g., pneumonia, tuberculosis).
Symptoms include persistent cough with purulent sputum, potential hemoptysis, finger clubbing, and other systemic complications.
Pathogenesis revolves around obstruction and chronic infection.

Morphology of Bronchiectasis

Gross: Typically affects lower lobes; severely dilated airways can be four times normal size.
Microscopic: Shows inflammatory exudate, ulceration, fibrosis, and necrosis of bronchioles.

Summary

Understanding atelectasis and COPD is vital for diagnosing and managing respiratory diseases, each carrying distinct pathophysiological mechanisms, clinical presentations, and potential complications.

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Description

This quiz focuses on the pathology of the respiratory system, including the definition and classification of atelectasis, as well as chronic obstructive airway diseases. It covers both gross and microscopic features of lesions and their correlation with clinical signs and symptoms. Test your knowledge on these vital topics in respiratory pathology.