Lecture 41

• Respiratory system


  Network of organs and tissues that help you breathe

  
• Components of the respiratory system

  • Nose
  • Lungs
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli

  
• Anatomical divisions of the respiratory system

  • Upper respiratory system (nose, nasal cavity, paranasal sinuses, pharynx)
  • Lower respiratory system (larynx, trachea, bronchi, bronchioles, alveoli)

  
• Functional divisions of the respiratory system

  • Conduction portion (facilitates air movement, temperature and humidity regulation, sound production)
  • Respiratory portion (facilitates gas exchange in alveoli)

  
• Respiratory mucosa lines the respiratory system and changes along the tract to ensure protection

  
• Respiratory mucosa


  • Consists of an epithelium and an underlying layer of areolar tissue
  • Ciliary action propels mucus across the epithelial surface

  
• Cystic fibrosis


  Congenital defect that affects mucus-producing cells, leading to thick sticky mucus which blocks respiratory passageways and leads to frequent infections
• Types of epithelium lining the respiratory tract

  • Pseudostratified ciliated columnar epithelium with numerous mucous cells (nasal cavity, superior pharynx, superior lower respiratory system)
  • Stratified squamous epithelium (inferior pharynx)
  • Cuboidal epithelium with scattered cilia (smaller bronchioles)
  • Simple squamous epithelium (alveoli)

  
• Nose and nasal cavity


  • Main passageway for air entry
  • Nasal vestibule traps large particles
  • Irregular bony surfaces cause air flow turbulence, allowing air to be warmed, humidified and particles to be trapped
• Significance of nasal respiration

  Warms and humidifies incoming air, dehumidifies and absorbs heat from outgoing air, protects delicate respiratory surfaces
• Mouth breathing bypasses the above processes
• Pharynx


  • Shared by digestive and respiratory systems
  • Nasopharynx has respiratory epithelium, oropharynx has stratified squamous epithelium

  
• Larynx


  • Cartilaginous tube that surrounds and protects the glottis (opening between vocal cords)
  • Composed of epiglottis, thyroid cartilage and cricoid cartilage

  
• Epiglottis


  "Guardian of the airways" - bends over glottis to prevent food from entering windpipe
• Laryngeal prominence (Adam's apple)


  Angle of thyroid cartilage, enlarges during puberty as a secondary sex characteristic
• Functions of the larynx

  • Provides an unobstructed airway
  • Routes air and food into proper channels
  • Produces voice through vibration of vocal cords

  
• Sound production by vocal cords

  1. Air passing through glottis vibrates vocal folds producing sound waves

  2. Pitch changed by changing tension of vocal cords

  3. Loudness increased by increasing force of air flow
• Trachea


  • Tough, flexible tube that branches into right and left main bronchi
  • Mucosa is ciliated columnar epithelium with mucus-producing glands
  • C-shaped cartilage rings keep trachea open and allow distortion when swallowing
• Bronchial tree


  • Right and left main bronchi divide into lobar bronchi, then segmental bronchi, then smaller bronchioles
• Respiratory bronchioles


  Connected to alveoli along alveolar ducts, end at alveolar sacs

  
• Alveoli structure


  • Lined by type I and type II pneumocytes
  • Surfactant produced by type II pneumocytes reduces surface tension to keep alveoli open
• Respiratory distress syndrome is caused by inadequate surfactant leading to alveolar collapse
• Key concepts to test

  • Functions of the respiratory system
  • Anatomical and functional divisions of the respiratory system
  • Components of the respiratory system and their functions
  • Differences in cell types lining the respiratory tract and their functions
  • Path of oxygen from atmosphere to alveolar sac