Respiratory System 1

• Respiration


  The process of delivering O2 to cells for the purpose of cellular respiration (energy production) and removing CO2
• Respiratory system


  • Requires a system of conduits (pipes)
  • Requires a large diffusion surface area
• Parts of the respiratory system

  • Respiratory tract (passageways)
  • Lungs (diffusion surface area)
• Upper respiratory tract


  • Nasal cavities
  • Pharynx
• Lower respiratory tract


  • Trachea
  • Bronchial tree
• Lungs


  • Apex
  • Base
• Bronchial tree


  • Consists of primary bronchi and 13 generations of their branches
  • 300,000 bronchioles in each lung
• Zones of the bronchial tree

  • Conducting zone
  • Respiratory zone
• Conducting zone


  • Walls of upper regions are composed of cartilage and smooth muscle lined with pseudostratified ciliated columnar epithelium
  • Walls of smaller tubes lined with cuboidal epithelium
  • No gas exchange occurs here
• Anatomical dead space volume


  Volume of gases in the upper respiratory tract and the conducting zone of the lower respiratory tract where gas exchange does not occur
• Respiratory zone


  • Extends from respiratory bronchioles to alveoli (150 million per lung)
  • Walls very thin (simple squamous epithelium)
  • Site of gas exchange
• Respiratory membrane (alveolar wall)


  • Endothelium of pulmonary capillaries
  • Type I alveolar cells (squamous epithelium 1 cell thick)
• Processes involved in gas exchange

  • Ventilation
  • External respiration
  • Gas transport
  • Internal respiration
  • Cellular respiration
• Ventilation


  The movement of gases between the atmosphere and the alveoli
• Intrapulmonary space


  The space within the lungs
• Intrapleural space


  The space between the parietal and visceral pleurae
• Intrapulmonary pressure


  At rest = atmospheric pressure (760 mm Hg at sea level)
• Gases move


  As a result of pressure differences between the atmosphere and the intrapulmonary space
• Boyle's law


  If temperature is held constant, the pressure of a gas varies inversely with its volume
• Inspiration


  1. Thorax expands

  2. Diaphragm descends

  3. Lung tissue is pulled outward

  4. Lungs are compliant

  5. Alveoli expand

  6. Intrapulmonary volume increases

  7. Intrapulmonary pressure decreases

  8. Air is drawn into alveoli
• Expiration


  1. Alveoli recoil

  2. Intrapulmonary volume decreases

  3. Intrapulmonary pressure increases

  4. Thoracic wall and lungs recoil

  5. Diaphragm relaxes

  6. Air is driven out of the lungs
• Hering-Breuer reflex


  • Stretch receptors in the lungs, visceral pleura and bronchioles are stimulated by inspiration
  • Impulses are sent to the respiratory centre (brainstem) terminating inspiration and initiating expiration
  • Prevents over-inflation of the lungs
• The trachea has smooth muscle tissue around it that can contract or relax to control airflow into the lungs
• Bronchial tree refers to all the branches of the bronchi within the lung
• The trachea consists of C-shaped cartilage rings that keep it open during breathing
• The bronchi are two tubes that branch off from the trachea into the lungs
• The trachea is the windpipe, which connects to the larynx (voice box) at its upper end.
• The trachea is the windpipe, which connects to the larynx
• Airway resistance is determined by the diameter of the airways
• Trachealis muscles contract during inspiration to pull apart the rings of cartilage in the trachea allowing more air to enter the lungs
• Larger diameter = less resistance
• Alveoli are tiny sacs where gas exchange occurs between blood vessels and air
• The trachea is made up of C-shaped cartilage rings that hold it open when we breathe.
• Cilia are hairlike projections on epithelial cells lining the trachea and bronchi
• Each bronchiole divides further until they reach alveolar ducts which lead directly into alveoli
• During exhalation, the trachealis muscles relax causing the rings of cartilage to come together narrowing the diameter of the trachea making it harder for air to leave the lungs
• Smaller diameter = more resistance
• Trachealis muscle surrounds the outside of the trachea and contracts to close off the trachea when swallowing
• The trachea divides into right and left main stem bronchi as they enter the lungs.
• Mucus produced by goblet cells in the epithelium lines the trachea and bronchi