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Questions and Answers
What are the four main components of the bronchi walls?
What type of epithelium is found in the preterminal bronchioles?
Simple columnar ciliated epithelium
Terminal bronchioles have goblet cells in their lining.
False
Which cells are responsible for the synthesis and secretion of pulmonary surfactant?
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The wall of the respiratory bronchioles is interrupted by the __________ and __________.
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What is the main function of Type I Pneumocytes?
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What do Alveolar Pores of Kohn help with?
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Study Notes
Bronchi
- Composed of Mucosa, Muscle coat, Submucosa, Cartilage, and Adventitia
- Mucosa contains respiratory epithelium
- Muscle coat contains two layers of smooth muscle fibers arranged in opposite directions
- Submucosa contains seromucous glands and lymphoid elements
- Cartilage contains irregular plates of hyaline cartilage and solitary lymphoid nodules
- Adventitia is the deepest layer separating the bronchus from surrounding tissues
Bronchioles
- Bronchi branch into bronchioles, which end in the pulmonary alveoli
- Three types of bronchioles: Preterminal, Terminal, and Respiratory
Preterminal Bronchioles
- Mucosa: Longitudinal fold
- Epithelium: Simple columnar ciliated epithelium with occasional goblet cells
- Lamina propria: Connective tissue rich in elastic fibers
- Smooth muscle: 2 helically arranged smooth muscle layers
- Adventitia: No cartilage, no seromucous, no lymph nodules
Terminal Bronchioles
- Similar structure to Preterminal bronchioles, but lined by simple columnar or simple cuboidal cells with partially ciliated epithelium and Clara cells
- No goblet cells
- Diameter less than 0.5 mm
- Clara cells: Secretory cells that secrete surfactants
Respiratory Bronchioles
- Each terminal bronchiole gives rise to two or three respiratory bronchioles
- Lined by simple ciliated cuboidal cells with a small number of non-ciliated Clara cells
- Lamina propria is rich in smooth muscle fibres and elastic fibers
- Wall of respiratory bronchioles is interrupted by alveolar sacs and alveolar ducts, where the tissue changes into simple squamous epithelium
Alveolar Region
- Alveolar duct: Thin, discontinuous lining of simple squamous epithelium. Lamina propria contains smooth muscle, which disappears distally and is replaced by elastic and reticular fibers
- Alveolar sacs: Formed by openings of several alveoli, attached to ducts. Wall of alveolar ducts consists almost entirely of pulmonary alveoli
Alveoli
- Specialized for oxygen and carbon dioxide exchange between air and blood
- Interalveolar septum: Lies between thin epithelial lining of two neighboring alveoli, contains a network of capillaries
- Interalveolar septum is supported by reticular and elastic fibers and sometimes contains fibroblasts, macrophages, and mast cells
Alveolar Structures
- Elastic fibers enable the alveoli to expand during inspiration and passively contract during expiration
- Reticular fibers support and prevent over-distention of the alveoli
- Septum contains pores (Alveolar Pores of Kohn) that help in the passage of air from one alveolus to another, equalizing pressure
Alveolar Epithelial Cells
- Type I Pneumocytes
- Type II Pneumocytes
- Macrophages or Dust cells
Type I Pneumocytes
- Line 95% of alveolar surfaces
- Simple squamous epithelium
- Function: Exchange of gases
Type II Pneumocytes
- Line 5% of alveolar surfaces
- Cuboidal or rounded cells with foamy cytoplasm and central nucleus
- Function:
- Synthesis and secretion of pulmonary surfactant
- Renewal of alveolar epithelial cells
Alveolar Macrophages - Dust cells
- Usually free in the alveolar lumen, also found in tissues between alveoli
- Derived from monocytes and are part of the mononuclear phagocyte system
- Function: Phagocytize foreign material, bacteria, and cellular debris in the alveoli
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Description
Explore the structure and function of bronchi and bronchioles in the respiratory system. This quiz covers the anatomy, including the layers of bronchi, various types of bronchioles, and their unique features. Test your knowledge on respiratory epithelium and smooth muscle organization.
