2. Microstructure of respiratory system Dr. Ashraf Hussain

3. Function of Respiratory System Gets air into and out of the body and allows gas exchange Olfaction Phonation Conducting portion –Nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles –Warms, moistens air Respiratory portion –Respiratory bronchioles, alveolar ducts, alveoli –Gas exchange occurs

5. Respiratory tree  trachea  main bronchus  lobar bronchus  segmental bronchus  conducting bronchiole  terminal bronchiole  respiratory bronchiole  alveolar duct  alveolar sac  alveolus

6. The human respiratory tree may consist of up to 28 generations

7. Layers of Wall Mucosa –Epithelium –Lamina propria (loose CT) –Smooth muscle Submucosa –Dense irregular CT –Glands often present Adventitia

8. Respiratory Epithelium In the conducting portion: –Ciliated columnar cells 30% –Mucous goblet cells 30% –Basal cells 30% –Generative stem cells that replace other cells --Brush cells (microvilli) 5% Sensory receptor cells –Small granule cell 5% Produce biogenic amines (catecholamines, serotinin, calcitonin) paracrine cells

10. Surface of Respiratory Mucosa Ciliated cell Goblet cell Brush cell

11. Small Granule Cell Electron micrograph of a cell of the diffuse neuroendocrine system. Note the accumulation of secretory granules (arrows) in the basal region of the cell. The Golgi complex seen in the upper part of the micrograph shows some secretory granules.

12. Immotile Cilia Syndrome A disorder that causes infertility in men and chronic respiratory tract infections in both sexes Immobility of cilia and flagella Deficiency of dynein

13. Smokers Alert

14. Smokers alert! Proportion of ciliated cells to goblet cells is altered to aid in clearing the increased particulate and gaseous pollutants Reduction in ciliated cells--- decreased movement of the mucous layer---- congestion of small airways

15. Respiratory epithelium Ciliated pseudostratified columnar epithelium Ciliated columnar cells Mucous goblet cells Brush cells (microvilli on their apical surface) Basal (short) cells Small granule cells (population of diffuse neuro endocrine system)

16. Stratified squamous epithelium Regions exposed to direct airflow or physical abrasions (e.g., oropharynx, epiglottis, vocal folds) It provides more protection from attrition than does typical respiratory epithelium

17. Nasal cavity Vestibule----sebaceous and sweat glands, Vibrissae—thick short hairs Nasal fossae– shelf like projections (conchae) Superior conchae covered with specialized olfactory epithelium Other two conchae covered by respiratory epithelium

18. Nasal Passage Turbinates

19. Nasal Cavity Vestibule (outer nasal area) –Keratinized epithelium transitions to respiratory –Short hairs filter Nasal Fossae –Chonchae Respiratory epith (pseudostratified squamous) Swell bodies; extensive venous system for countercurrent flow to warm air. Olfactory epithelium of superior choncha

20. Nasal Mucosa E – Epithelium M – Mucous glands of lamina propria S – Serous glands of lamina propria V – Thin walled venules

21. Sinuses

22. Epithelium Lining of Sinus Thinner respiratory epithelium that contains few goblet cells.

23. Epiglottis: stratifified squamous epithelium False vocal cords: respiratory epithelium True vocal cords: stratified squamous epithelium

24. Respiratory Structures

25. Trachea Lined with typical respiratory mucosa 16-20 “C”shaped rings of hyaline cartilage

30. Bronchiole Neither cartilage nor glands in mucosa Scattered goblet cells within the epithelium Pseudostratified columnar epithelium, which decreases in height and complexity to become ciliated simple columnar or cuboidal epithelium in smaller terminal bronchioles Terminal bronchioles contain Clara Cells

32. Functions of Clara cells Produce one of the components of surfactant Act as reserve cells, i.e. they are able to divide, differentiate and replace other damaged cell types Contain enzyme systems which can detoxify noxious substances

33. Transition of terminal bronchioles into alveolar ducts