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• Respiration


  Utilization of oxygen in the metabolism of organic molecules by cells, termed internal or cellular respiration

  
• Respiration


  Exchange of oxygen and carbon dioxide between an organism and the external environment
• Alveoli


  • Air-containing sacs, sites of gas exchange with the blood

  
• Respiratory Cycle


  Inspiration & expiration
• Right ventricle


  • Pumps blood through the pulmonary arteries and arterioles and into the capillaries surrounding each alveolus

  
• Upper Airways


  • Bronchioles - first airway branches that no longer contain cartilage
• Conducting Zone


  • Contains no alveoli, does not exchange gases with the blood

  
• Respiratory Zone


  • Contains alveoli, is the region of gas exchange with the blood

  
• Type I Alveolar Cells

  • Continuous layer, one cell thick, of flat epithelial cells
• Type II Alveolar Cells


  • Interspersed between Type I cells, thicker, specialized cells that produce surfactant to prevent alveolar collapse
• Intercostal Muscles


  • Groups of muscles that run between the ribs
• Ventilation


  Occurs when Patm is greater than Palu, Palu is greater than Patm, and Palu is less than Path
• Transpulmonary pressure


  The difference in pressure between alveolar and intrapleural spaces

  
• Inspiration


  Intrapleural pressure becomes more subatmospheric, air moves from atmosphere into respiratory tract

  
• Expiration


  Inspiratory muscles stop contracting 2. Chest wall recoils inward, intrapleural pressure increases 3. Transpulmonary pressure decreases 4. Lungs recoil, alveolar pressure increases above atmospheric pressure, air flows out

  
• Lung Mechanics


  • Ability to add/remove air from lungs (compliance) 2. Overcoming surface tension in alveoli 3. Different lung volumes used to assess function

  
• Lung Compliance


  Magnitude of change in lung volume produced by a given change in transpulmonary pressure

  
• Determinants of Compliance


  • Stretchability of lung tissues, surface tension at air-water interfaces in alveoli

  
• Surfactant


  Detergent-like substance that reduces cohesive forces between molecules on the alveolar surface
• Law of Laplace


  Describes relationship between pressure, surface tension, and radius of an alveolus
• Factors determining Airway Resistance

  • Tube length, tube radius, interactions between moving molecules. Most important is radius of airways.

  
• Tidal Volume


  Volume of air inspired or expired during normal breathing
• Minute Ventilation


  Tidal Volume x Respiratory Rate

  
• Alveolar Ventilation


  Tidal Volume - Dead Space

  
• Dead Space


  Volume of inspired air that does not take part in gas exchange, composed of anatomical and alveolar dead space
• Pressure of a gas

  Proportional to temperature and concentration of the gas
• Increasing the rate of total body oxygen consumption does not increase the PO2 in alveoli

  
• Factors determining Alveolar PO2

  • PO2 of atmospheric air, rate of alveolar ventilation, rate of total-body oxygen consumption

  
• Diffusion of oxygen occurs from blood to cells, net diffusion of carbon dioxide occurs from cells to blood
• Increasing the temperature of gas molecules increases their rate of movement and pressure
• Systemic Arterial Blood


  Contains 200mL oxygen, more than 98% bound to hemoglobin, remainder dissolved
• Hemoglobin


  • Four subunits: Heme (contains iron that binds oxygen), Globin (polypeptide)

  
• Hemoglobin Saturation


  Percent of hemoglobin that has oxygen or other gas bound to its iron moiety

  
• 98.5% of total oxygen in blood is bound to hemoglobin

  
• Transport of Oxygen in Blood

  Dissolved in plasma, reversibly combined with hemoglobin in erythrocytes

  
• Medullary Respiratory Center


  • Dorsal respiratory group (inspiratory neurons), Ventral Respiratory group (respiratory rhythm generator), receives input from peripheral and central chemoreceptors

  
• Pontine Respiratory Centers


  • Apneustic Center (fine-tunes inspiratory neuron activity), Pneumotaxic Center (modulates Apneustic Center)

  
• Excreted substances are filtered at the glomerulus and secreted by tubular cells

  
• Renal Processes


  Amount excreted = Amount filtered + Amount secreted - Amount reabsorbed

  
• 20% of plasma entering glomerular capillaries is filtered into Bowman's space, remaining 80% leaves via efferent arteriole