Respiratory System

• Primary functions of the respiratory system

  • Supply body's need for oxygen and give off CO2
  • Maintain homeostasis and normal pH
  • Participate in body's immune defense
  • Olfactory sensation
  • Phonation
  • Excretion (CO2)
• Anatomic divisions of the respiratory system

  • Upper Respiratory tract (Nasal cavity, Pharynx, larynx)
  • Lower respiratory tract (Trachea, Bronchi, lungs)
• Functional divisions of the respiratory system

  • Conducting portion (passage) (Nasal cavity, Pharynx, Larynx, bronchi)
  • Respiratory portion (gas exchange) (Alveolar ducts, Alveolar sacs, alveoli)
• Nasal cavity


  First passageway of air, with 2 components: External vestibule and Internal nasal cavity (olfactory portion, respiratory portion)
• Nasal vestibule


  Lined with skin and vibrissae (hair), keratinized stratified squamous
• Nasal mucosa


  Pseudostratified ciliated columnar, with goblet cells, basal cells, neuroendocrine cells, brush cells, Klutchitsky cells, and a lamina propria with seromucous glands, cavernous venous plexus, and lymphoid elements
• Olfactory portion of nasal cavity


  Contains olfactory cells (bipolar neurons), supporting cells, and basal cells (stem cells replace olfactory neurons every 2-3 months), with respiratory epithelium
• Paranasal sinuses


  Bilateral cavities in the frontal, maxillary, ethmoid, and sphenoid bones, with respiratory epithelium (thinner) and lamina propria
• Nasopharynx


  Conducts air from nasal cavity to larynx, with respiratory epithelium
• Oropharynx


  Conducts air from nasal cavity to larynx, with non keratinized stratified squamous
• Pharyngeal tonsil


  Located in the posterior of the nasopharynx
• Palatine tonsil


  Located at the junction of the oral cavity and oral pharynx
• Larynx


  Conducts air from pharynx to trachea, with respiratory epithelium and cartilage
• Epiglottis


  Elastic cartilage that stands in front of the laryngeal inlet and bends posteriorly to cover the inlet, with non keratinized stratified squamous epithelium on the upper surface and lamina propria with mucous and serous glands
• Structures in the larynx

  • Superior vestibular folds (respiratory epithelium)
  • Inferior vocal folds (non keratinized stratified squamous)
• Trachea


  Respiratory epithelium with goblet cells, ciliated columnar cells, basal cells, and DNES cells, with trachealis smooth muscle and hyaline cartilage
• Primary bronchi


  Right is wider and shorter, more vertical with 3 secondary bronchi. Left is narrower and less vertical with 2 secondary bronchi. Respiratory epithelium with C shaped cartilage.
• Intrapulmonary bronchi


  Respiratory epithelium with seromucous glands in the submucosa
• Structures of the bronchial tree

  • Bronchi
  • Bronchiole
• Bronchiole


  Smaller airways deriving from tertiary bronchi, surrounded by smooth muscle, with respiratory epithelium but no cartilage or mucosal glands
• Types of bronchioles


  • Large bronchiole (ciliated columnar)
  • Small bronchiole (ciliated cuboidal with Clara cells)
• Clara cells


  Dome shaped secretory cells that secrete glycoproteins and surfactant, degrade toxins, divide to replace cells, and have antimicrobial properties
• Alveolar ducts/sacs


  Arise from terminal bronchioles, with a linear arrangement of alveoli
• Alveoli


  Lined with type I (flat dark oval nucleus, thin cytoplasm) and type II (polygonal, divide to replace type I, secrete surfactant) pneumocytes, with septa, alveolar macrophages (dust cells), and a rich blood supply for gas exchange
• Surfactant


  Decreases surface tension to prevent alveolar collapse