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  2. 2. VENTILATING PORTION: - diaphragm, intercostal muscles, elastic tissue in lungs - means by which air is moved in and out of lungs continuously CONDUCTING PORTION: - nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles - warm/cool, humidify, filter & conduct incoming air to respiratory passageways - lined with respiratory epithelium RESPIRATORY PORTION: -respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli -site of exchange of O2 and CO2 between blood and alveoli 3 DIVISIONS OF RESPIRATORY SYSTEM Nasal cavity Nasopharynx Oropharynx Larynx Trachea Br B RB AD A Lung Diaphragm
  3. 3. NASAL CAVITY & PARANASAL AIR SINUSES - Respiratory area is lined with pseudostratified ciliated columnar epithelium with goblet cells and is highly vascularized - Olfactory area (roof of nasal cavity and superior concha) is lined with olfactory epithelium – specialized bipolar (sensory) neurons with sustentacular (supporting) cells and basal cells (stem cells) SAGITTAL VIEW CORONAL VIEW O R
  4. 4. CELLS OF RESPIRATORY EPITHELIUM •Ciliated cells – most abundant, tall with basal nuclei, lots of mitochondria to provide ATP for ciliary beating of mucus and its’ trapped particulate matter. •Goblet cells - ~30% of cells, have narrow basal stem containing nucleus and most organelles and apical theca containing mucinogen which becomes hydrated to form mucus. •Basal cells – ~30% of cells, lie on basal lamina, do not reach apical surface. Undifferentiated stem cells that will give rise to other cell types. •Brush cells - ~3% of cells, narrow columnar cells with tall microvilli. Thought to have sensory receptors on basal surfaces and act as sensory receptors. •DNES cells -~3% of cells – have numerous small granules in their basal cytoplasm whose contents act on other cells of the respiratory epithelium
  5. 5. Ciliated cells Basal body beneath cilia Goblet cell Brush cell RESPIRATORY EPITHELIUM Microvilli Basal cell Small granule cell (DNES, Enteroendocrine)
  6. 6. RESPIRATORY EPITHELIUM Plasma cells Basement membrane Basal cell Lymphocyte Cilia with basal bodies Ciliated cell Goblet cell
  7. 7. OLFACTORY EPITHELIUM •Olfactory cells – bipolar neurones, apical dendrite ends in olfactory vesicle from which non-motile cilia with receptors for odiferous substances arise. When a threshold level of receptors are occupied an action potential is generated and transmitted to the olfactory bulb via axon which passes through cribiform plate to synapse in olfactory bulb. •Sustentacular cells – tall columnar cells with microvilli. Provide physical support, nourishment and electrical insulation for olfactory cells. •Basal cells – stem cells to replace olfactory and sustentacular cells. •Bowman’s glands – provide serous fluid to refresh olfactory cilia. Basal cell Olfactory cell Sustentacular cell Bowman’s gland Dendrite Olfactory vesicle Olfactory cilia
  8. 8. Olfactory epithelium, 68a (H&E) OLFACTORY EPITHELIUM Olfactory cell Sustentacular cell Basal cell
  9. 9. THE PHARYNX The NASOPHARYNX serves only as an air passageway. It is lined with pseudostratified ciliated columnar epithelium The OROPHARYNX and LARYNGOPHARYNX serve as passageways for both air and food. They are lined with stratified squamous epithelium (for protection). The muscular wall of the entire pharynx consists of skeletal muscle
  10. 10. THE LARYNX Vestibular fold Vocal fold Cricoid cartilage All cartilages hyaline except epiglottis (elastic). Vocal ligaments are elastic ligaments. Laryngeal ventricle
  11. 11. Larynx, 69b (H&E) THE LARYNX Skeletal (arytenoid) muscles Stratified squamous non-keratinized epithelium of vocal fold Pseudostratified ciliated columnar epithelium of vestibular fold and ventricle Vocal ligament Mixed glands
  13. 13. THE TRACHEA •Mucosa lined with respiratory epithelium which continuously propels mucus and debris towards the larynx •Seromucous glands in submucosa help produce mucus ‘sheets’ •16-20 C-shaped rings of hyaline cartilage prevent the trachea from collapsing. Closed posteriorly by trachealis (smooth) muscle - allows oesophagus to expand anteriorly when swallowing. •10cm long, 2.5cm diam. flexible tube, divides at carina (T4) into right and left primary bronchi
  14. 14. Trachea, 70a (H&E) THE TRACHEA Cartilage Seromucous glands Trachealis muscle Respiratory epithelium Thyroid
  15. 15. Hyaline cartilage Trachea, 70a (H&E) Respiratory epithelium Mixed seromucous glands Mucus acinusSerous demilune
  16. 16. BRONCHI •Primary bronchi run obliquely in the mediastinum, enter lung where they subdivide into secondary and tertiary bronchi •Mucosa and submucosa similar to trachea. Inc. smooth muscle & elastic fibers in lamina propria. Mixed glands in submucosa. •Plates of hyaline cartilage encircle bronchus and prevent collapse.
  17. 17. Lung, 72a (H&E) – bronchi and bronchioles Bronchi LUNG
  18. 18. WALL OF A BRONCHUS Hyaline cartilage Respiratory epithelium Lumen Blood vessels and glands
  19. 19. Alveoli (surrounded by fine elastic fibers) Bronchus (cartilage & smooth muscle in wall) Bronchiole ( no cartilage, just smooth muscle in wall) Terminal bronchiole Respiratory bronchiole (alveoli off walls) Alveolar duct Alveolar capillary network
  20. 20. CELLS LINING BRONCHIOLES Ciliated cell Basal cell Clara cell Clara (bronchiolar) cells – columnar cells with domed apices and short blunt microvilli. Apical cytoplasm filled with secretory granules containing surfactant-like material that reduces surface tension and faciliates patency of bronchioles. Cells also degrade inhaled toxins.
  21. 21. BRONCHIOLE As tubes become smaller, resp. epithelium becomes lower with fewer goblet and ciliated cells. Terminal bronchioles are lined with simple cuboidal epithelium. Proportion of smooth muscle increases allowing for constriction (para.) and dilation (symp.) of airways. Lumen Smooth muscle Clara cells
  22. 22. BRONCHIOLAR EPITHELIUM ClaraCil Brush Clara SEM TEM Cil Cil
  23. 23. Terminal bronchiole Alveolar duct Alveoli Respiratory bronchioles RESPIRATORY BRONCHIOLES Respiratory bronchioles – first structures in respiratory zone, alveoli arise from their walls, terminate in alveolar ducts Alveolar ducts – linear arrangements of alveoli, lined with type I cells, isolated regions of smooth muscle cells in lamina propria between adjacent alveoli, lead to alveolar sacs
  24. 24. Type I Type II Resp. bronchiole Alveolar duct Smooth muscle Atrium or alveolar sac RESPIRATORY REGION OF THE LUNG
  25. 25. ALVEOLI Type II cells Capillary Dust cell (macrophage) Type I cell Capillary Alveolus (airspace) ~ 250 million alveoli in lungs provide 140m2 of surface area for gaseous exchange Interalveolar septumSurfactant
  26. 26. CELLS OF ALVEOLAR WALLS •Type I cells (squamous alveolar cells) - highly attenuated, cover 97% of surface area of alveolus, organelles grouped around nucleus so most cytoplasm virtually free of organelles. Joined to other type I and type II cells by tight junctions to prevent leakage of fluid into air space. Basement membrane fuses with that of endothelial cell to minimise thickness of respiratory membrane. •Type II cells (septal cells) – account for 60% of alveolar cells but only 3% of surface area. Cytoplasm filled with lamellar bodies which contain surfactant that lowers alveolar surface tension. They divide to form new Type II and type I cells. •Alveolar macrophages (dust cells) – derived from monocytes, found in alveolar septa, migrate between type I cells to enter lumen of alveolus, phagocytose dust and bacteria and migrate to bronchioles where ciliary action carries them to the pharynx to be swallowed. Over 2 million dust cells are cleared per hr.
  27. 27. ALVEOLI & INTERALVEOLAR SEPTUM Alveolar pores connect adjacent alveoli – allow for equalization of pressure and alternate routes for blocked passages Type II cell Type I cell Endothelial cell Capillary Dust cell Alveolar poresAlveoli Respiratory membrane
  28. 28. THE BLOOD-AIR BARRIER •Surfactant •Type I cell •Basement membrane •Endothelial cell Barrier is extremely thin (15 times thinner than a piece of paper) to facilitate gaseous exchange Red blood cell Endothelium Type I cell Fused basal laminae Alveolus
  29. 29. Interface between capillary and alveolus
  31. 31. Netter 201 Bronchial artery CIRCULATION WITHIN THE LUNGS Pulmonary artery (next to air passages) Pulmonary veins (in septum)