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
LungConducting portion
Intrapulmonary bronchi Bronchioles Terminal bronchioles
Respiratory portion Respiratory bronchioles Alveolar ducts Alveoli
Airways – conducting portionBronchi (extra
pulmonary)TracheaLarynxPharynx (naso – oro –
laringo-)Nasal cavity/mouth –
paranasal sinuses
Function To provide O2To eliminate CO2 from cellsBy respirationBreathing/ventilation (in – out - lung)External respiration (CO2-O2 exchange - in
blood) – respiratory portion - lungTransport of gases – to cellsInternal 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/transportFilter clean moistened - warm
Nasal cavity
Walls - bordersnasal septum - bone - cartilageBony wall - ala nasi – cartilageOpenings:
Nares/nostrils – anterior Choanae – posterior
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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 GlandsSerous GlandsVenous SinusesMucoperiosteum or Mucoperichondrium
Secretions of nasal mucosa- Bactericides - Lysozymes
Nasal Cavity
Olfactory regionRoof-nasal cavity, superior aspect-nasal septum,
concha superiorOlfactory 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 - serousCapillary plexus
Olfactory Epithelium
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Paranasal sinuses
Frontal-maxillary-ethmoid-sphenoidParanasal sinuses - nasal cavityMucosa ≈ posterior nasal cavity
Respiratory epithelium
Lamina propria Seromucous gland Lymphoid tissue
Periosteum
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Pharynx (naso-oro-laringo)
MucosaRespiratory epitheliumStratified squamous epitheliumLamina propria – loose-dense irreguler CT
VascularizedSeromucous glandLymphoid tissue – posterior: pharyngeal tonsil
Skeletal muscle-epimysium
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Larynx – voice box Additional function:
PhonationPrevent 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 bronchusMucosa
Respiratory epithelium – pseudostratified ciliated columnar epithelium: goblet, cilated columnar, basal, brush, serous, DNES cells
L propria – loose fibroelastic-mucous, seromucous gl-lymphoid tissue
--elastic laminaSubmucosa-dense irreg. fibroelastic CT, mucous-
seromucous gl- lymphoid tissueAdventitia – fibroelastic CT - C ring hyaline cartilage (p
cartilaginea) – fibrous CT – smooth muscle (p. membranacea)
Trachea Epithelium
Lamina propria
Submucosa
Adventitia
C shape cartilage
Trachea
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)
BronchiolesMucosa
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 bronchiolesMost distal conducting
portionCiliated simple cuboidal
epithelium with Clara cellsLamina propria –
fibroelastic CTSmooth muscle cellsAdventitia-elastic fibers
Terminal Bronchiole
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Alveolar walls & Alveolar cells
Lung
Respiratory brochiolesSimilar – terminal br.Wall – alveoli – gas exchange
Alveolar ductWall ≈ alveoli ends into alveolar sac
Alveolar sacCluster of alveoliOpen – 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 Kohn8-60 µmRim: 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 – bloodSurfactantPneumocyte I – thin regionFused basal laminaeEndothelial cell – continuous capillary
Defense mechanism
Vibrissae – filter large particlesMucus – trap smaller particlesCough reflex – expectorationAlveolar macrophages – phagocytoseLymphoid tissue – specific immune response
Pleura
Mesothelial cellsConnective tissue
Pleural effusion - fluidHaemothorax - bloodPneumothorax - airPleuritis - infection
Clinical correlation Normal
Smooth muscle-bronchioles – para sympathetic Inpiration – relax Expiration-end –contract
Asthmaprolonged contraction –
expiration Lumen << – wheezing, dyspnea Hypersecretion goblet cell,
mucus/serous glSteroids, Β2-agonist -relax
Premature infant surfactant << - respiratory
distress syndromeSynthetic surfactantGlucocorticoid
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, 2nd ed. Philadelphia; Saunders:2001
Thank you
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