Histology of the respiratory system

Objectives  Discuss the microscopic features of Nasal cavity.  Discuss the microscopic features of Epiglottis.  Discuss the microscopic features of Larynx.  Discuss the microscopic features of Trachea.  Discuss the microscopic features of lung.

Respiratory system  Lung  Conducting portion  Intrapulmonary bronchi  Bronchioles  Terminal bronchioles  Respiratory portion  Respiratory bronchioles  Alveolar ducts  Alveoli  Airways – conducting portion  Bronchi (extra pulmonary)  Trachea  Larynx  Pharynx (naso – oro – laringo-)  Nasal cavity/mouth – paranasal sinuses

Function  To provide O2  To eliminate CO2 from cells  By respiration  Breathing/ventilation (in – out - lung)  External respiration (CO2-O2 exchange - in blood) – respiratory portion - lung  Transport of gases – to cells  Internal respiration (CO2-O2 exchange- in the vicinity of cells)

Breathing/ventilation  Thoracic cage: parietal – visceral pleura  lung – pleural cavity – thin film - serous lubricant  Muscles: inter costal – scalenus –abdominal, etc.  Diaphragm  Elastic – collagen fibers – lung  via conducting portion – function  As conduit/ airways/transport  Filter  clean  moistened - warm

Nasal cavity  Walls - borders  nasal septum - bone - cartilage  Bony wall - ala nasi – cartilage  Openings:  Nares/nostrils – anterior  Choanae – posterior

Jeanne Adiwinata Pawitan

Nasal cavity  Anterior portion – vestibule: vibrissae – skin - sebaceous + sweat glands  Posterior aspect – nasal fossae: resp ep - conchae (sup, mid, inf), olfactory region, Kiesselbach area: arterial plexuses and venous sinuses  bleeding

Nasal Cavity  Keratinized stratified squamous epithelium  Non Keratinized stratified squamous epithelium  Pseudostratified ciliated columnar epithelium with goblet cells  Olfactory Epithelium

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

Nasal Cavity

Olfactory region  Roof-nasal cavity, superior aspect-nasal septum, concha superior  Olfactory epithelium - yellow  Olfactory cells- bipolar neuron: dendrite end - olfactory vesicle – olfactory cilia – odor receptor  Sustentacular cells, basal cells source: Gartner  Lamina propria  Bowman’s gland - serous  Capillary plexus

Olfactory Epithelium

Jeanne Adiwinata Pawitan

Paranasal sinuses  Frontal-maxillary-ethmoid-sphenoid  Paranasal sinuses - nasal cavity  Mucosa ≈ posterior nasal cavity  Respiratory epithelium  Lamina propria  Seromucous gland  Lymphoid tissue  Periosteum

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Pharynx (naso-oro-laringo)  Mucosa  Respiratory epithelium  Stratified squamous epithelium  Lamina propria – loose-dense irreguler CT  Vascularized  Seromucous gland  Lymphoid tissue – posterior: pharyngeal tonsil  Skeletal muscle-epimysium Jeanne Adiwinata Pawitan

Larynx – voice box  Additional function:  Phonation  Prevent food/drinks – respiratory system  Tube : cartilage (hyaline, elastic) – ligaments – skeletal muscles (intrinsic-extrinsic)  Epiglottis – elastic cartilage  Stratified squamous non keratinized epithelium  Pseudostratified (respiratory epithelium)  Vestibular fold – false vocal cord (superior)  Vocal fold - true vocal cord (inferior) - stratified squamous  Vocalis muscle  vocal ligament – regular dense elastic CT

Trachea–extrapulmonary bronchus  Mucosa  Respiratory epithelium – pseudostratified ciliated columnar epithelium: goblet, cilated columnar, basal, brush, serous, DNES cells  L propria – loose fibroelastic-mucous, seromucous gl-lymphoid tissue --elastic lamina  Submucosa-dense irreg. fibroelastic CT, mucous- seromucous gl- lymphoid tissue  Adventitia – fibroelastic CT - C ring hyaline cartilage (p cartilaginea) – fibrous CT – smooth muscle (p. membranacea)

Trachea Epithelium Lamina propria Submucosa Adventitia C shape cartilag e

Trachea

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Terminal Bronchiole

Lung

Respiratory Bronchiole

Lung  Intrapulmonary bronchus (2ndary -3tiary: lobe – broncho pulmonary segment)  Mucosa –folded app  Respiratory epithelium  L propria – fibroelastic- seromucous gl-lymphoid nodules --Smooth muscles-spiral  Submucosa-seromucous gl-lymphoid nodules  Adventitia – plates of cartilage (hyaline)  Bronchioles  Mucosa  Pseudostratified columnar epithelium- goblet cells  ciliated simple columnar  ciliated cuboidal (with Clara cells)  Lamina propria  No glands  Elastic fibers  Smooth muscles – helical loose meshwork – surrounded by fibroelastic CT

Lung  Terminal bronchioles  Most distal conducting portion  Ciliated simple cuboidal epithelium with Clara cells  Lamina propria – fibroelastic CT  Smooth muscle cells  Adventitia-elastic fibers

Terminal Bronchiole

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Alveolar walls & Alveolar cells

Lung  Respiratory brochioles  Similar – terminal br.  Wall – alveoli – gas exchange  Alveolar duct  Wall ≈ alveoli  ends into alveolar sac  Alveolar sac  Cluster of alveoli  Open – common space - atrium

Alveolar cells

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Alveolus  Small air sac - gas exchange  Between alveoli – interalveolar septum – alveolar pores  Connective tissue: elastic, reticular (coll III) – lymphoid tissue  Macrophages, fibroblast, myofibroblast, mast cells  Continuous capillary bed (from pulmonary artery  vein)  Both side  Type I pneumocytes/alveolar cells - squamous alveolar cells) – tight junction – basal lamina – very thin region  permeable to gasses  Type II pneumocytes/alveolar cells - great alveolar cell – septal cells – surfactant – surface tension↓  ≠ collapse

Alveolus  Alveolar macrophages  Monocytes  Migrate – through pneumocytes I  lumen alveolus  phagocytose surfactant, particulate matter (dust, bacteria)  dust cells  bronchy – cilia– swallowed/ expectorated  Migrate back - connective tissue - interpulmonary septum  lymph vessel  Alveolar pores of Kohn  8-60 µm  Rim: fusion cell membrane – two pneumocytes I – both side - interalveolar septum  In alveolar septum  air communication between alveoli  Function: equalize air pressure

Blood gas barrier  Gas exchange – thinnest region – interalveolar septum: alveolar lumen – blood  Surfactant  Pneumocyte I – thin region  Fused basal laminae  Endothelial cell – continuous capillary

Defense mechanism  Vibrissae – filter large particles  Mucus – trap smaller particles  Cough reflex – expectoration  Alveolar macrophages – phagocytose  Lymphoid tissue – specific immune response

Pleura  Mesothelial cells  Connective tissue  Pleural effusion - fluid  Haemothorax - blood  Pneumothorax - air  Pleuritis - infection

Clinical correlation  Normal  Smooth muscle-bronchioles – para sympathetic  Inpiration – relax  Expiration-end –contract  Asthma  prolonged contraction – expiration  Lumen << – wheezing, dyspnea  Hypersecretion goblet cell, mucus/serous gl  Steroids, Β2-agonist -relax  Premature infant  surfactant << - respiratory distress syndrome  Synthetic surfactant  Glucocorticoid  maturation of pneumocyte II  Emphysema  Longterm exposure- cigarette smoke ≈ inh – antitrypsin >< elastase – dust cells – elastic fiber destructed

Source of pictures  Norton NS. Netter’s head and neck anatomy for dentistry. Philadelphia; Saunders:2007.  Gartner LP, Hiatt JL. Color textbook of Histology, 2 nd ed. Philadelphia; Saunders:2001

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