Histology of Respiratory Tract

1. Histology of Respiratory Tract Dr. SamaulHaque Dr. Safaa

2. Objectives • Differentiate between the olfactory and nasal mucosa. • Discuss the microscopic structure of larynx. • Describe the microscopic structure of trachea and lungs. • Differentiate between the terminal and respiratory bronchioles. • Explain alveolar cells.

3. Respiratory System • This consists of the lungs and the air passages that lead to and form the lungs. • The air passages branch as they enter the lungs to finally form alveoli. • This system has 3 functions: 1.Air conduction; 2.Air filtration; 3.Gas exchange (respiration).

4. Air passages consist of: • A conducting portion • A respiratory portion • Conducting portion • 1.Nasal cavities; 2.Nasopharynx and oropharynx; 3.Larynx; 4.Trachea; 5.Paired primary bronchi. Bronchi within the lungs branch extensively to form bronchioles. The terminal bronchioles form the last part of the conducting system.

5. The respiratory portion is the part of the tract where gaseous exchange takes place and includes: 1.Respiratory bronchioles; 2.Alveolar ducts; 3.Alveolar sacs; 4.Alveoli.

7. Respiratory Epithelium • The typical respiratory epithelium consists of 5 cell types: 1.Ciliated cells; 2.Goblet cells; 3.Brush cells (have short blunt microvilli); 4.Small granule cells (contain secretory granules); 5.Basal cells (stem cells).

8. Nasal Cavity • Keratinized stratified squamous epithelium • Non Keratinized stratified squamous epithelium • Pseudostratified ciliated columnar epithelium with goblet cells • Olfactory Epithelium

9. Nasal Cavity • Nasal Cavity formed of: • 1.Vestibule. 2.Respiratory segment. 3.Olfactory segment • Vestibule: Keratinized stratified squamous epithelium Non Keratinized stratified squamous Contains vibrissae (fine hair), sebaceous glands and sweat glands

10. Nasal Cavity • Respiratory segment - Respiratory Epithelium - Lamina Propria • Olfactory segment - Olfactory Epithelium: i. Olfactory cells (bipolar neurons) ii. Basal cells iii. Supportive cells - Lamina Propria

11. Nasal Cavity

12. Lamina Propria • Mucous Glands • Serous Glands • Venous Sinuses • Mucoperiosteum or Mucoperichondrium • Secretions of nasal mucosa - Bactericides - Lysozymes

13. Olfactory Epithelium

14. Nasopharynx Mucosa • Respiratory Epithelium • Stratified Squamous Epithelium Lamina Propria • Elastic Tissue • Mucus Gland

15. Larynx • Mucosa False vocal cords: Pseudostratified ciliated columnar epithelium True vocal cords: Non Keratinized stratified squamous epithelium • Intrinsic Muscles • Cartilages - Larger Laryngeal Cartilages (Hyaline)

16. Larynx

17. Epiglottis • Mucosa Anteriorly (Lingual mucosa): Non Keratinized stratified squamous epithelium Posteriorly: (Laryngeal mucosa): Pseudostratified ciliated columnar epithelium • Elastic Cartilage

18. Epiglottis

19. Trachea • Mucosa • Pseudostratified ciliated columnar epithelium • Lamina propia • Sub mucosa • Connective Tissue • Seromucousbronchial Glands • Hyaline Cartilage • Adventitia

20. Trachea

21. Trachea

22. Lung

23. Bronchi • Mucosa; • Pseudostratified ciliated columnar epithelium • Lamina propia • Muscularis; • Submucosa; • Connective Tissue • SeromucousGlands • Cartilage layer; • Adventitia. Connective Tissue • At 1 mm diameter, the cartilage plates disappear and it becomes a bronchiole.

24. Respiratory Bronchioles Alveolar Ducts And Alveoli

25. Intrapulmonary Bronchus

26. Terminal Bronchiole

27. Respiratory Bronchiole Simple cuboidal epithelium

28. Alveolar Cells • Alveolar Epithelial Cells (Type I Pneumocyte) • Type II Pneumocyte • Interalveolar Pores • Alveolar Macrophages (dust cells) • Alveolar Surfactant

29. Alveolar walls & Alveolar cells

30. Alveolar walls & Alveolar cells

31. Respiratory Membrane • It is the area where gas exchange occurs. It is formed of: • Alveolar Epithelium. • Fused basement membranes of the alveolar epithelium and the capillary endothelium. • Capillary Endothelium.

32. Thank you