RESPIRATORY

• Respiratory System Components

  • Nasal Cavities
  • Pharynx
  • Larynx
  • Trachea
  • Bronchial Tree and Lungs
  • Pleural Membranes

  
• Respiratory System


  • Provides for O2 and CO2 exchange to and from the blood
  • Ventilating Mechanism
  • Thoracic cage
  • Intercostal muscles
  • Diaphragm
  • Elastic components of the lungs

  
• Anatomic Division of Respiratory System

  • Upper Respiratory Tract
  • Lower Respiratory Tract

  
• Functional Division of Respiratory System

  • Conducting Portion: air flows to the respiratory portion, cleans and humidifies inspired air
  • Respiratory Portion: gas exchange occurs

  
• Conducting Portion


  Nasal Cavity→ Terminal Bronchioles

  
• Respiratory Portion


  • Respiratory bronchioles, alveolar ducts and alveoli

  
• Components of Nasal Cavities

  • Vestibule
  • Nasal Cavity
• Vestibule


  • Includes sweat glands, sebaceous glands, and coarse moist vibrissae (hairs)
  • Looses keratinization and transition from stratified squamous epithelium to pseudostratified columnar epithelium
• Nasal Cavity


  • Lies within the skull as two cavernous chambers separated by osseous nasal septum
  • Conchae or turbinate bones extends from each lateral walls
  • Lined by pseudostratified columnar epithelium
  • Underlying loops of capillaries for warming inspired air
  • Seromucous glands – humidifies inspired air and mucus traps particulate and air impurities
• Respiratory Epithelium Cell Types

  • Ciliated Columnar Cells
  • Goblet Cells
  • Brush Cells
  • Small Granule Cells (Kulchitsky Cells)
  • Basal Cells

  
• Ciliated Columnar Cells


  Most abundant, each with 250-300 cilia on its apical surface
• Goblet Cells


  Numerous and predominate in some areas, with basal nuclei and apical domains filled with granules of mucin glycoproteins
• Brush Cells


  • Less numerous, columnar cell type, in which a small apical surface bears sparse, blunt microvilli
  • Chemosensory receptors – resembles gustatory cells, with similar transduction components and synaptic contact with afferent nerve endings on their basal surfaces
• Alveoli


  are the cellular sites of O2 and CO2 exchange between inspired air and blood
• Small Granule Cells (Kulchitsky Cells)


  Numerous granules, similar to endocrine cells of the gut, are part of the Diffue Neuroendocrine System (DNES)
• Basal Cells


  Mitotically active stem and progenitor cells that give rise to the other epithelial cells
• Olfactory Epithelium Cell Types

  • Olfactory Neurons
  • Supporting Cells
  • Basal Cells
• Olfactory Neurons


  • Bipolar neurons present throughout the epithelium
  • Apical pole is its dendrite end and has a knob-like swelling with dozen basal bodies from which long cilia project into the overlying aqueous layer
  • Cilia provides large surface for transmembrane chemoreceptors
  • Responds to odoriferous substances by generating an action potential along the axons extending from the basal ends
  • Enters the brain through a foramina in the cribriform plate as Cranial Nerve I (Olfactory Nerve)
• Supporting Cells

  • Columnar cells with narrow bases and broad cylindrical apexes containing the nuclei and extending microvilli into the fluid layer
  • Well developed junctional complexes bind the supporting cells to the olfactory cells
  • Express ion channels which help maintain a microenvironment conductive to olfactory function and survival
• Basal Cells


  • Small spherical or cone-shaped cells near the basal lamina
  • Stem cells for the other two types of cells
  • Replaces the olfactory neurons every 2-3 months
  • Replaces support cells less frequently
• Lamina propria possess large serous glands, Olfactory Glands (of Bowman), which produce constant flow of fluid surrounding the olfactory cilia and facilitating access of new odoriferous substances
• Paranasal Sinuses


  • Bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones of the skull
  • Lined with a thinner respiratory epithelium having fewer goblet cells

  
• Parts of Pharynx

  • Nasopharynx
  • Oropharynx
• Nasopharynx


  • Nasal cavities open posteriorly into the Nasopharynx, the first part of the pharynx
  • Continuous caudally with the oropharynx, the posterior part of the oral cavity leading to the larynx and esophagus
  • Connected to the each middle ear cavity through the auditory tubes
  • Lined with Respiratory Epithelium

  
• Oropharynx


  Lined with Stratified Squamous Epithelium
• Larynx


  • A short passage for air between the pharynx and the trachea
  • Rigid wall is reinforced by hyaline cartilages and smaller elastic cartilages, all of which are connected by ligaments
  • Maintains an open airway
  • Movement participate in the sound conduction during phonation
• Laryngeal Structures

  • Epiglottis
  • Vestibular Folds
  • Vocal Cords/ Folds
• Epiglottis


  • Flattened structure projecting from the upper rim of the larynx
  • Stratified squamous epithelium in transition to ciliated pseudostratified columnar epithelium
  • Mixed mucous and serous glands in the lamina propria

  
• Vestibular Folds

  • Immovable
  • Typical respiratory epithelium
  • Numerous sero-mucinous glands and lymphoid nodules
• Vocal Cords/ Folds

  • Non-keratinized stratified squamous epithelium (abrasion and desiccation)
  • Vocal Ligaments – a dense irregular connective tissue (supports the free edges)
  • Vocalis Muscle – large bundles of striated fibers (allows movements)
• Trachea

  • Lined with typical respiratory epithelium (Ciliated Pseudostratified Columnar Epithelium)
  • Lamina propria: numerous seromucinous glands producing watery mucus
  • C-shaped cartilages located between the submucosa and adventitia
  • Maintains the shape of trachea and keeps it open
  • Trachealis muscle – a bundle of smooth muscle tissues
  • Relaxes during swallowing to allow passage of food
  • Allows the esophagus to bulge into the lumen of the trachea
• Bronchial Tree Components

  • Trachea
  • Primary Bronchi
  • Secondary Bronchi (Lobar)
  • Tertiary Bronchi (Segmental)
  • Terminal Bronchioles

  
• Bronchi

  • Epithelium: Respiratory (Ciliated Pseudostratified Columnar Epithelium)
  • Cartilage rings completely encircle the lumen, as the bronchial diameter decreased, cartilage rings are gradually replaced with smaller isolate plates of hyaline cartilage
  • Small mucous and serous glands are abundant with ducts opening into the bronchial lumen
  • Lamina propria contains numerous lymphocytes as well as MALT and smooth muscle and elastic fibers
• Bronchioles


  • Intralobular airways with diameter of 1mm or less
  • Lack both mucosal glands and cartilage
  • Epithelium: From Ciliated Pseudostratified Columnar Epithelium → Ciliated Simple Columnar Epithelium or Ciliated Simple Cuboidal Epithelium in the smallest Terminal Bronchioles
• Bronchiole Components

  • Mucociliary Apparatus or Escalator
  • Club Cells or Bronchiolar Exocrine Cells
  • Brush Cells
  • Stem Cells
• Mucociliary Apparatus or Escalator


  • Ciliated Epithelium
  • Clears the debris and mucus by moving it upward along the bronchial tree and trachea
• Club Cells or Bronchiolar Exocrine Cells


  • Located at the Terminal Bronchiole Epithelium
  • Non-ciliated, dome-shaped apical ends containing secretory granules
  • Functions: Secretion of surfactant – lipoproteins and mucins in the fluid layer on the epithelial surface
  • Detoxification of inhaled xenobiotic compounds by enzymes of the SER
  • Secretion of antimicrobial peptides and cytokines for local immune defense
• Respiratory Bronchioles


  • Each terminal bronchiole subdivides into two or more Respiratory Bronchioles
  • Always include a saclike Alveoli
  • Represent the first-part of the Respiratory Region
  • Bronchiolar mucosa resemble that of the Terminal Bronchioles except for having few openings to alveoli where gas exchange occurs
  • Epithelium consist of Club Cells, with simple squamous cells at the alveolar openings and extending into the alveolus

  
• Alveolar Ducts


  • Distal branches of Respiratory Bronchioles
  • Lined completely by the openings of alveoli (extremely attenuated squamous cells)

  
• Alveolar Sacs

  • Large clusters of alveoli that forms the ends of alveolar ducts distally
  • Lamina propria contains web of elastic and reticular fibers that encircles the alveolar opening and closely surrounds each alveolus
  • Network of capillaries that also surrounds each alveolus