Airways and Lungs Sanjaya Adikari Department of Anatomy.
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Transcript of Airways and Lungs Sanjaya Adikari Department of Anatomy.
![Page 1: Airways and Lungs Sanjaya Adikari Department of Anatomy.](https://reader038.fdocuments.net/reader038/viewer/2022103004/56649c955503460f94951e71/html5/thumbnails/1.jpg)
Airways and Lungs
Sanjaya Adikari
Department of Anatomy
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Nasal Cavity
Nasopharynx
(Oropharynx)
Larynx
Trachea
Bronchi
……….
Upper respiratory tract
Lower respiratory tract
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Trachea
Primary bronchi
Secondary bronchi
Tertiary bronchi
Bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
L & R bronchi
Lobar bronchi
Segmental bronchi
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Nasal cavity
• Hair at the entrance to trap bigger particles
• Mucous and serous glands to produce secretions to trap smaller particles and moisturize the air
• Highly vascular to increase air temperature
• Folds on the nasal walls to increase the surface area
• Pseudostratified columnar ciliated epithelium which traps and moves up the dust particles
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General histological arrangement of the airway
• Mucosa
• Smooth muscle layer
• Submucosa
• Cartilage layer
• Adventitia
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Changes in the arrangement
• PSCC epithelium in large air ways become simple cuboidal nonciliated epithelium in small air ways
• Frequently seen goblet cells become less frequent and totally absent in terminal bronchioles
• The layer of smooth muscles becomes thicker as it goes down and becomes maximum at terminal bronchioles
• Serous and mucous glands in submucosal connective tissue becomes less numerous and absent beyond tertiary bronchi
• Cartilage parts smaller in small airways
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Trachea
• Pseudostratified columnar ciliated
epithelium
• Smooth muscle layer almost absent
• Numerous serous mucous glands in the
submucosa
• 'C' shaped hyaline cartilage
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Primary and secondary bronchi
• Less taller respiratory epithelium
• Smooth muscle layer discontinuous
• Fewer serous and mucous glands
• Few hyaline cartilage plates rather than 'C'
shaped ones
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Tertiary bronchi
• Tall simple columnar ciliated epithelium
• Smooth muscle layer continuous
• Very fewer serous and mucous glands
• Few small irregular hyaline cartilage plates
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Bronchioles
• Airways < 1 mm in diameter
• Simple columnar ciliated epithelium
• Smooth muscle layer continuous and
prominent
• Serous and mucous glands absent
• Cartilage plates absent
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Terminal bronchioles
• Structure is as same as the other
bronchioles
• End of the purely conducting portion of the
airway Respiratory bronchioles
• Walls contain small number of single alveoli
• Ciliated cuboidal epithelium. No goblet cells
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Alveolar ducts
• Numerous alveolar sacs open into these
• Simple cuboidal nonciliated epithelium
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Alveolar wall• Type I pneumocytes (The squamous cells)
– Forms part of the gaseous diffusion barrier
• Type II pneumocytes
– Produce surfactant
• Connective tissue
– Reticulin, collagen and elastic fibres with fibroblasts.
– Macrophages.
• Blood vessels, mainly capillaries
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Respiratory barrier/Gaseous diffusion barrier
Type I pneumocyte
Common BM
Capillary endothelial cell
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Alveolar pores
• Equalize the pressure between the alveoli
• Collateral circulation of air when the
bronchiole is obstructed
• Responsible for easy spread of infection eg.
Lobar pneumonia
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Pleura