Microscopic Structure of Respiratory System

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Questions and Answers

What type of epithelial cells line the vocal cords?

Cuboidal epithelial cells

Columnar epithelial cells

Stratified squamous epithelial cells (correct)

Pseudostratified, tall, columnar, ciliated epithelial cells

What is the function of type II pneumocytes in the lung?

Gas exchange

/filtering out particles

Regulating airway tone

Producing pulmonary surfactant (correct)

What is the term for the solidification of pulmonary tissue due to bacterial invasion?

Empyema

Pneumonitis

Pleurisy

Consolidation (correct)

What is the term for a type of pneumonia characterized by patchy consolidation of the lung?

Bronchopneumonia Signup and view all the answers

Which of the following is NOT a way to classify bacterial pneumonia?

Age of the patient Signup and view all the answers

What is the function of the basement membrane in the alveolar wall?

To separate the endothelial cells from the alveolar lining epithelial cells Signup and view all the answers

What is the term for the type of epithelial cells that cover 95% of the alveolar surface?

Type I pneumocytes Signup and view all the answers

What is the term for the type of cells that are the main cell type involved in the repair of alveolar epithelium?

Type II pneumocytes Signup and view all the answers

What is the characteristic gross appearance of the lung in the stage of gray hepatization?

Grayish brown and dry Signup and view all the answers

What is the final stage of resolution in pneumonia?

Enzymatic digestion and resorption Signup and view all the answers

What is a complication of pneumonia?

Empyema Signup and view all the answers

What is the definition of chronic bronchitis?

Persistent cough with sputum production for at least 3 months in at least 2 consecutive years Signup and view all the answers

What is chronic asthmatic bronchitis?

Chronic bronchitis with intermittent bronchospasm and wheezing Signup and view all the answers

What is the paramount influence in the pathogenesis of chronic bronchitis?

Cigarette smoking Signup and view all the answers

What is a histologic feature of small airways in young smokers?

Goblet cell metaplasia with mucous plugging of the lumen Signup and view all the answers

What is a consequence of chronic irritation by inhaled substances in chronic bronchitis?

Fibrosis of the bronchiolar wall Signup and view all the answers

What is the most common cause of lobar pneumonia?

Pneumococci Signup and view all the answers

What is the primary mechanism by which the respiratory system clears out pathogens?

Mucociliary apparatus Signup and view all the answers

Which of the following is NOT a factor that can interfere with the phagocytic action of alveolar macrophages?

Cough reflex Signup and view all the answers

What is the characteristic of the lung in the first stage of congestion in lobar pneumonia?

Heavy, boggy, and red Signup and view all the answers

Which of the following conditions is characterized by the accumulation of secretions in the lungs?

Cystic fibrosis Signup and view all the answers

What is the term used to describe the consistency of the lung in the stage of red hepatization?

Liver-like Signup and view all the answers

Which of the following is a common agent of bronchopneumonia?

All of the above Signup and view all the answers

What is the primary factor that makes the extremes of life (infancy and old age) more vulnerable to disease?

Weakened immune system Signup and view all the answers

What is the characteristic histologic feature of chronic bronchitis?

Enlargement of the mucus-secreting glands of the trachea and bronchi Signup and view all the answers

What is the main feature of bronchial asthma?

Hyper-reactive airways leading to episodic broncho-constriction Signup and view all the answers

What is the term for the type of asthma that is initiated by a type I hypersensitivity reaction?

Extrinsic asthma Signup and view all the answers

What is the characteristic feature of bronchiolitis obliterans?

Obliteration of lumens due to fibrosis Signup and view all the answers

What is the term for the type of asthma that is associated with increased susceptibility to generate immunoglobulin E (IgE)?

Atopic asthma Signup and view all the answers

What is the characteristic feature of the bronchial epithelium in chronic bronchitis?

Squamous metaplasia and dysplasia Signup and view all the answers

What is the term for the state of unremitting attacks of asthma?

Status asthmaticus Signup and view all the answers

What is the characteristic feature of bronchioles in chronic bronchitis?

Marked narrowing due to goblet cell metaplasia Signup and view all the answers

What is a non-immune mechanism that can initiate intrinsic asthma?

Ingestion of aspirin Signup and view all the answers

What is the result of increased airway hyperreactivity in intrinsic asthma?

Bronchospasm after exposure to certain agents Signup and view all the answers

What cells are responsible for antigen presentation in the pathogenesis of asthma?

Dendritic cells Signup and view all the answers

What is a characteristic histologic finding in asthma?

Thickening of the basement membrane of the bronchial epithelium Signup and view all the answers

What are the whorls of shed epithelium in the mucous plugs of asthma known as?

Curschmann spirals Signup and view all the answers

What is the characteristic feature of the inflammatory infiltrate in the bronchial walls of asthma?

Prominence of eosinophils Signup and view all the answers

What is the effect of prolonged bronchoconstriction on the bronchial wall muscle in asthma?

Hypertrophy of the muscle Signup and view all the answers

What is the characteristic gross finding in the lungs of patients with asthma?

Overdistension and atelectasis Signup and view all the answers

Study Notes

Respiratory System Diseases

Microscopic Structure of the Respiratory Tree

The entire respiratory tree, including the larynx, trachea, and bronchioles, is lined by pseudostratified, tall, columnar, ciliated epithelial cells, heavily admixed in the cartilaginous airways with mucus-secreting goblet cells.
The vocal cords are covered by stratified squamous epithelium.

Microscopic Structure of the Alveolar Walls

The capillary endothelium lining the intertwining network of anastomosing capillaries.
A basement membrane and surrounding interstitial tissue separating the endothelial cells from the alveolar lining epithelial cells.
Alveolar epithelium, comprising a continuous layer of two principal cell types:
- Flattened, plate-like pavement type I pneumocytes (or membranous pneumocytes) covering 95% of the alveolar surface.
- Rounded type II pneumocytes, which are important for producing pulmonary surfactant and repairing alveolar epithelium after destruction of type I cells.

Bacterial Pneumonia

Bacterial invasion of the lung parenchyma leads to exudative solidification (consolidation) of the pulmonary tissue.
Classification may be made according to:
- Etiologic agent (e.g., pneumococcal or staphylococcal pneumonia).
- The nature of the host reaction (e.g., suppurative, fibrinous).
- The gross anatomic distribution of the disease (lobular bronchopneumonia versus lobar pneumonia).

Bronchopneumonia

Characterized by patchy consolidation of the lung, usually representing an extension of a preexisting bronchitis or bronchiolitis.
Common in the more vulnerable two extremes of life--infancy and old age.
Caused by agents such as staphylococci, streptococci, pneumococci, Haemophilus influenzae, and Pseudomonas aeruginosa.

Lobar Pneumonia

An acute bacterial infection of a large portion of a lobe or of an entire lobe.
Caused by pneumococci (Streptococcus pneumoniae) in 90 to 95% of cases.
Four stages of the inflammatory response:
1. Congestion, characterized by vascular engorgement, intra-alveolar fluid with few neutrophils.
2. Red hepatization, characterized by massive confluent exudation with red cells and neutrophils filling the alveolar spaces.
3. Gray hepatization, characterized by progressive disintegration of red cells and the persistence of fibrino-suppurative exudates.
4. Resolution, characterized by the digestion of consolidated exudates within the alveolar spaces, producing a granular, debris-filled appearance.

Complications of Pneumonia

Tissue destruction and necrosis, causing abscess formation.
Spread of infection to the pleural cavity, causing empyema.
Bacteremic dissemination to the heart valves, pericardium, brain, kidneys, spleen, or joints, causing metastatic abscesses, endocarditis, meningitis, or suppurative arthritis.

Chronic Bronchitis

Defined clinically as present in any patient who has persistent cough with sputum production for at least 3 months in at least 2 consecutive years.
In simple chronic bronchitis, patients have a productive cough but no physiologic evidence of airflow obstruction.
Some individuals may demonstrate hyper-reactive airways with intermittent bronchospasm and wheezing, known as chronic asthmatic bronchitis.

Pathogenesis of Chronic Bronchitis

Two sets of factors are important in the genesis of chronic bronchitis:
- Chronic irritation by inhaled substances.
- Microbiologic infections.
Cigarette smoking remains the paramount influence.

Morphology of Chronic Bronchitis

Grossly, there may be hyperemia, swelling, and excessive mucinous to mucopurulent secretions layering the epithelial surfaces.
The characteristic histologic feature of chronic bronchitis is enlargement of the mucus-secreting glands of the trachea and bronchi.
The bronchial epithelium may exhibit squamous metaplasia and dysplasia.
There is marked narrowing of bronchioles caused by goblet cell metaplasia, mucous plugging, inflammation, and fibrosis.

Bronchial Asthma

A chronic relapsing inflammatory disorder characterized by hyper-reactive airways, leading to episodic, reversible broncho-constriction, owing to increased responsiveness of the tracheobronchial tree to various stimuli.
Most asthma is associated with atopy, which represents increased susceptibility to generate immunoglobulin E (IgE) in response to external allergens.
Asthma has traditionally been divided into two basic types:
- Extrinsic asthma, initiated by a type I hypersensitivity reaction induced by exposure to an extrinsic antigen.
- Intrinsic asthma, initiated non-immune mechanisms, including ingestion of aspirin, pulmonary infections, especially viral, cold, inhaled irritants, stress, and exercise.

Pathogenesis of Asthma

Antigen presentation by the dendritic cell with the lymphocyte and cytokine response leading to airway inflammation and asthma symptoms.
Some of the principal cells identified in airway inflammation include mast cells, eosinophils, epithelial cells, macrophages, and activated T lymphocytes.

Morphology of Asthma

Grossly, the lungs are overdistended because of overinflation, and there may be small areas of atelectasis.
The most striking macroscopic finding is occlusion of bronchi and bronchioles by thick, mucous plugs.
Histologically, the mucous plugs contain whorls of shed epithelium, which give rise to the well-known Curschmann spirals.
Numerous eosinophils and Charcot-Leyden crystals are present.
The other characteristic histologic findings of asthma include thickening of the basement membrane of the bronchial epithelium, edema, and an inflammatory infiltrate in the bronchial walls, with a prominence of eosinophils.

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Description

This quiz covers the microscopic structure of the respiratory tree and alveolar walls, including epithelial cells and capillary endothelium.