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Respiratory System


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Respiratory System

  2. 2. Respiration <ul><li>The term respiration includes 3 separate functions: </li></ul><ul><li>Ventilation: </li></ul><ul><ul><li>Breathing. </li></ul></ul><ul><li>Gas exchange: </li></ul><ul><ul><li>Occurs between air and blood in the lungs. </li></ul></ul><ul><ul><li>Occurs between blood and tissues. </li></ul></ul><ul><li>0 2 utilization: </li></ul><ul><ul><li>Cellular respiration. </li></ul></ul>
  3. 3. Gas Pressures <ul><li>The air in the atmosphere that surrounds the earth is a mixture of gases: </li></ul><ul><li>Nitrogen </li></ul><ul><li>Oxygen </li></ul><ul><li>CO 2 </li></ul><ul><li>Water vapor (H 2 O) </li></ul><ul><li>Inert gases (Ar, Ne, Ze, Kr) </li></ul>
  4. 5. Partial Pressures <ul><li>Partial pressure of each gas = percent of total pressure (760 torr or mm Hg = 1 atm) </li></ul><ul><li>Partial pressure of any gas depends on the fraction of the total that is made up of that gas </li></ul><ul><li>Total pressure may vary depending on conditions eg. altitude, hyperbaric chamber </li></ul><ul><li>PP of a gas not same in lung as in atmosphere due to change in composition as air goes down respiratory passageways to lung (CO 2  , H 2 O vapor  , O 2  ) </li></ul>
  5. 7. Respiratory Anatomy
  6. 8. Nasal passages & Pharynx trachea esophagus nasopharynx (food) (air)
  7. 9. Conducting Zone <ul><li>All the structures through which air passes before reaching the respiratory zone. </li></ul><ul><li>Warms and humidifies inspired air. </li></ul><ul><li>Filters and cleans: Mucus secreted trap particles in the inspired air. </li></ul><ul><li>Mucus moved by cilia to be expectorated. </li></ul>
  8. 10. Trachea Next Slide
  9. 12. Mechanics of Respiration Ventilating the Lung - getting air into and out of the lung Inspiration and Expiration
  10. 13. Pressure - Volume Relation <ul><li>Volume of a container and the pressure of the gases within it are inversely related. </li></ul><ul><li>If the container can be made larger , the pressure of the gas inside it will decrease . </li></ul><ul><li>An example would be pulling on the plunger of a syringe: the pressure inside the syringe decreases and fluid is sucked in due to the lower pressure inside. </li></ul>
  11. 14. This principle governs the movement of air into and out of the lung. Muscles of inspiration shown in the next slide cause the thoracic cavity to expand and the lung is “pulled” open, thus reducing the air pressure in the lung. Since the pressure in the air around us (atmospheric pressure) is higher, air will move from the region of higher pressure to the region of lower pressure, and fill the expanding lung. Expiration at rest is a rather “passive” process and relies on the elastic recoil of the lung and thoracic wall to reduce the size, increase the pressure in the lung (“intrapulmonic”), and force the air out. During exercise, muscles contract more forcefully, and the process is more “active”.
  12. 17. Intrapulmonary and Intrapleural Pressures <ul><li>Visceral and parietal pleurae are flush against each other. The intrapleural space contains only a film of fluid secreted by the membranes. </li></ul><ul><li>Lungs normally remain in contact with the chest wall. Lungs expand and contract along with the thoracic cavity. </li></ul>
  13. 18. Intrapulmonary and Intrapleural Pressures <ul><li>Intrapulmonary pressure: </li></ul><ul><ul><li>Intra-alveolar pressure (pressure in the alveoli). </li></ul></ul><ul><li>Intrapleural pressure: </li></ul><ul><ul><li>Pressure in the intrapleural space is negative. </li></ul></ul><ul><ul><ul><li>Due to lack of air in the intrapleural space. </li></ul></ul></ul>
  14. 20. Physical Aspects of Ventilation <ul><li>Ventilation occurs as a result in pressure differences induced by changes in lung volume. </li></ul><ul><li>Physical properties that affect lung function: </li></ul><ul><ul><li>Compliance. </li></ul></ul><ul><ul><li>Elasticity. </li></ul></ul><ul><ul><li>Surface Tension. </li></ul></ul>
  15. 21. Compliance <ul><li>Distensible (stretchable). </li></ul><ul><li>Ease with which the lungs can expand. </li></ul><ul><li>Change in lung volume per change in transpulmonary pressure. </li></ul><ul><li>  V/  P </li></ul><ul><li>100 x more distensible than a balloon. </li></ul><ul><li>Compliance reduced by factors that produce resistance to distension. </li></ul>
  16. 22. Elasticity <ul><li>Tendency to return to initial size after distension. </li></ul><ul><li>High content of elastin proteins. </li></ul><ul><ul><li>Very elastic and resist distension. </li></ul></ul><ul><ul><li>Recoil ability. </li></ul></ul><ul><li>Elastic tension increases during inspiration and is reduced by recoil during expiration. </li></ul>
  17. 23. Surface Tension <ul><li>Force that resists distension. </li></ul><ul><li>Exerted by fluid in alveoli. </li></ul><ul><li>Surfactants act like detergents to reduce surface tension and make it easy to expand the alveoli. </li></ul><ul><li>If surface tension is high much energy must be used to expand alveoli, (if they can open at all). </li></ul><ul><li>Newborns that lack surfactant - hyaline membrane disease. </li></ul>
  18. 24. Ventilation <ul><li>Mechanical process to move air in and out of the lungs. </li></ul><ul><li>O 2 of air is higher in the lungs than in the blood, O 2 diffuses from air to the blood . </li></ul><ul><li>C0 2 moves from the blood to the air by diffusing down its concentration gradient. </li></ul><ul><li>Gas exchange occurs entirely by diffusion . </li></ul><ul><li>Diffusion is rapid because of the large surface area and the small diffusion distance . </li></ul>
  19. 25. Alveoli <ul><li>Polyhedral in shape and clustered like units of honeycomb. </li></ul><ul><li>~ 300 million air sacs. </li></ul><ul><ul><li>Large surface area (60 – 80 m 2 ). </li></ul></ul><ul><li>Each alveolus is 1 cell layer thick. </li></ul><ul><li>Total air barrier is 2 cells across (2  m). </li></ul><ul><li>2 types of cells: </li></ul><ul><li>Alveolar type I: </li></ul><ul><ul><li>Structural cells. </li></ul></ul><ul><li>Alveolar type II: </li></ul><ul><ul><li>Secrete surfactant. </li></ul></ul>
  20. 30. Regulation of Breathing <ul><li>Neurons in the medulla oblongata forms the rhythmicity center: </li></ul><ul><ul><li>Controls automatic breathing. </li></ul></ul><ul><li>Brain stem respiratory centers: </li></ul><ul><ul><li>Medulla. </li></ul></ul><ul><ul><li>Pons. </li></ul></ul>
  21. 31. <ul><li>Apneustic center: </li></ul><ul><ul><li>Promote inspiration by stimulating the inspiratory neurons in the medulla. </li></ul></ul><ul><ul><li>Provide constant stimulus for inspiration. </li></ul></ul><ul><li>Pneumotaxic center: </li></ul><ul><ul><li>Antagonize the apneustic center. </li></ul></ul><ul><ul><li>Inhibits inspiration. </li></ul></ul>Pons Respiratory Centers
  22. 32. Chemoreceptors <ul><li>2 groups of chemoreceptors that monitor changes in blood P C02 , P 02 , and pH. </li></ul><ul><li>Central: </li></ul><ul><ul><li>Medulla. </li></ul></ul><ul><li>Peripheral: </li></ul><ul><ul><li>Carotid and aortic bodies. </li></ul></ul><ul><ul><li>Control breathing indirectly via sensory nerve fibers to the medulla. </li></ul></ul>
  23. 34. Chemoreceptors <ul><li>2 groups of chemoreceptors that monitor changes in blood P C02 , P 02 , and pH. </li></ul><ul><li>Central: </li></ul><ul><ul><li>Medulla. </li></ul></ul><ul><li>Peripheral: </li></ul><ul><ul><li>Carotid and aortic bodies. </li></ul></ul><ul><ul><li>Control breathing indirectly via sensory nerve fibers to the medulla. </li></ul></ul>
  24. 36. Chemoreceptor Control <ul><li>Chemoreceptor input modifies the rate and depth of breathing. </li></ul><ul><ul><li>Oxygen content of blood decreases more slowly because of the large “reservoir” of oxygen attached to hemoglobin. </li></ul></ul><ul><ul><li>Chemoreceptors are more sensitive to changes in P C02 . </li></ul></ul><ul><li>H 2 0 + C0 2 </li></ul><ul><li>Rate and depth of ventilation adjusted to maintain arterial PC02 of 40 mm Hg. </li></ul>H 2 C0 3 H + + HC0 3 -
  25. 37. Chemoreceptor Control <ul><li>Peripheral chemoreceptors: </li></ul><ul><ul><li>Are not stimulated directly by changes in arterial P C02 . </li></ul></ul><ul><li>C0 2 </li></ul>H 2 C0 3 H +
  26. 40. Ventilation Patterns <ul><li>Eu pnea - Normal, quiet breathing </li></ul><ul><li>Dyspnea - Difficult breathing </li></ul><ul><li>Apnea - absence of breathing </li></ul><ul><li>Tachypnea - Rapid breathing rate </li></ul><ul><li>Bradypnea - Slow breathing </li></ul><ul><li>Hyperpnea - Deep breathing </li></ul><ul><li>Hypopnea - Shallow breathing </li></ul><ul><li>Hyperventilation - Rapid, deep breathing </li></ul><ul><li>Cheyne-Stokes breathing - periods of apnea interspersed with hyperpnea </li></ul>
  27. 41. Hemoglobin and 0 2 Transport <ul><li>280 million hemoglobin/ RBC. </li></ul><ul><li>Each hemoglobin has 4 polypeptide chains and 4 hemes. </li></ul><ul><li>Each heme has 1 atom iron that can combine with 1 molecule 0 2 . </li></ul>
  28. 42. Hemoglobin <ul><li>Hemoglobin production controlled by erythropoietin. </li></ul><ul><li>Production stimulated by P 02 delivery to kidneys. </li></ul><ul><li>Loading/unloading depends: </li></ul><ul><ul><li>P 02 of environment. </li></ul></ul><ul><ul><li>Affinity between hemoglobin and 0 2 . </li></ul></ul>
  29. 44. Oxyhemoglobin Dissociation Curve <ul><li>Loading and unloading of 0 2 . </li></ul><ul><li>Steep portion of the curve, small changes in P 02 produce large differences in % saturation (unload more 0 2 ). </li></ul><ul><li>Decreased pH, increased temp., and increased 2,3 DPG: affinity of Hb for 0 2 decreases. </li></ul><ul><li>Shift to the right greater unloading. </li></ul>
  30. 46. <ul><li>C0 2 transported in the blood: </li></ul><ul><ul><li>HC0 3 - (70%). </li></ul></ul><ul><ul><li>Dissolved C0 2 (10%). </li></ul></ul><ul><ul><li>Carbaminohemoglobin (20%). </li></ul></ul>C0 2 Transport
  31. 50. Respiratory Acidosis <ul><li>Hypoventilation. </li></ul><ul><li>Accumulation of CO 2 in the tissues. </li></ul><ul><li>pH decreases. </li></ul><ul><li>Plasma HCO 3 - increases. </li></ul><ul><li>P c02 increases. </li></ul>
  32. 51. Respiratory Alkalosis <ul><li>Hyperventilation. </li></ul><ul><li>Excessive loss of CO 2 . </li></ul><ul><li>pH increases. </li></ul><ul><li>Plasma HCO 3 - decreases. </li></ul><ul><li>P CO 2 decreases. </li></ul>