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Airways and Lungs. Sanjaya Adikari Department of Anatomy. Nasal Cavity Nasopharynx (Oropharynx). Upper respiratory tract. Larynx Trachea Bronchi ………. Lower respiratory tract. Trachea Primary bronchi Secondary bronchi Tertiary bronchi Bronchioles Terminal bronchioles - PowerPoint PPT Presentation
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Airways and Lungs
Sanjaya AdikariDepartment of Anatomy
Nasal CavityNasopharynx (Oropharynx)
LarynxTrachea Bronchi……….
Upper respiratory tract
Lower respiratory tract
TracheaPrimary bronchi Secondary bronchi Tertiary bronchi Bronchioles Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacsAlveoli
L & R bronchiLobar bronchiSegmental bronchi
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
General histological arrangement of the airway
• Mucosa• Smooth muscle layer • Submucosa • Cartilage layer • Adventitia
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
Trachea
• Pseudostratified columnar ciliated epithelium
• Smooth muscle layer almost absent
• Numerous serous mucous glands in the submucosa
• 'C' shaped hyaline cartilage
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
Tertiary bronchi
• Tall simple columnar ciliated epithelium
• Smooth muscle layer continuous
• Very fewer serous and mucous glands
• Few small irregular hyaline cartilage plates
Bronchioles• Airways < 1 mm in diameter
• Simple columnar ciliated epithelium
• Smooth muscle layer continuous and prominent
• Serous and mucous glands absent
• Cartilage plates absent
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
Alveolar ducts
• Numerous alveolar sacs open into these
• Simple cuboidal nonciliated epithelium
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
Respiratory barrier/Gaseous diffusion barrier
Type I pneumocyte
Common BM
Capillary endothelial cell
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
Pleura
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