Respiratory Physiology I

• Primary functions of the respiratory system:

  • Provide extensive surface area for gas exchange between air and circulating blood
  • Move air to and from exchange surfaces of lungs
• Non-respiratory functions of the respiratory system:

  • Immune functions: protect respiratory surfaces from dehydration, temperature changes, and pathogens
  • Olfactory sense: detection of odors
  • Regulation of pH: dependent on the rate of CO2 release
• Functions of the upper respiratory system:

  • Warm incoming air to body temperature
  • Humidify incoming air to 100% humidity
  • Filter incoming air through the mucociliary escalator
• Functions of the lower respiratory system:

  • Exchange of gases
  • Protection with free alveolar macrophages and surfactant produced by type II alveolar cells
• Anatomical organization of the respiratory system:

  • Upper respiratory system: structures above the larynx
  • Lower respiratory system: includes the larynx and structures inferior to the larynx
• Components of the respiratory system:

  • Nasal cavity, pharynx, trachea, bronchioles, bronchus, lungs, diaphragm, ribs, etc.
• Functional (Physiological) Organization of the respiratory system:

  • Conducting portion: passageways that carry air to and from exchange surfaces
  • Respiratory portion: respiratory bronchioles and alveoli where gas exchange takes place
• Respiratory defense system:

  • Consists of filtration mechanisms to remove foreign particles and pathogens
  • Includes mucous cells, mucous glands, cilia, and alveolar macrophages
• In gas exchange, distances involved are short and total surface area is large
• Blood flow and airflow are coordinated in gas exchange processes
• Dalton's Law states that each gas in a mixture of gases exerts a pressure independent of other gases present
• Fick's Law of Diffusion states that factors affecting diffusion include surface area, partial pressure gradient, membrane permeability and thickness, diffusion distance, capillary transit time, and ventilation perfusion ratio
• Factors affecting gas diffusion include gradient, membrane thickness, fluid in interstitial space, membrane surface area, solubility of gases, capillary transit time, and ventilation to perfusion ratio
• Boyle's Law defines the relationship between gas pressure and volume, stating that they are inversely related in a contained gas at constant temperature
• Pulmonary ventilation involves the physical movement of air into and out of the respiratory tract, creating volume changes that lead to pressure changes
• Respiratory patterns include quiet breathing (eupnea) involving active inhalation and passive exhalation, and forced breathing (hyperpnea) involving active inhalation and exhalation assisted by accessory muscles