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RESPIRATORY PHYSIOLOGY

RESPIRATORY PHYSIOLOGY. 5 Functions of the Respiratory System. Provides extensive gas exchange surface area between air and circulating blood Moves air to and from exchange surfaces of lungs. 5 Functions of the Respiratory System. 3. Protects respiratory surfaces from outside

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RESPIRATORY PHYSIOLOGY

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  1. RESPIRATORY PHYSIOLOGY

  2. 5 Functions of the Respiratory System • Provides extensive gas exchange surface area between air and circulating blood • Moves air to and from exchange surfaces of lungs

  3. 5 Functions of the Respiratory System 3. Protects respiratory surfaces from outside environment 4. Produces sounds 5. Participates in olfactory sense

  4. Components of the Respiratory System Figure 23–1

  5. Organization of the Respiratory System • The respiratory system is divided into the upper respiratory system, above the larynx, and the lower respiratory system, from the larynx down

  6. The Respiratory Tract • Consists of a conducting portion: • from nasal cavity to terminal bronchioles • Consists of a respiratory portion: • the respiratorybronchioles and alveoli

  7. What is the difference between external respiration and internal respiration?

  8. Respiration • Refers to 2 integrated processes: • external respiration • internal respiration

  9. External Respiration • Includes all processes involved in exchanging O2 and CO2 with the environment

  10. Internal Respiration • Also called cellular respiration • Involves the uptake of O2 and production of CO2 within individual cells

  11. What are the major steps involved in external respiration?

  12. 3 Processes of External Respiration • Pulmonary ventilation (breathing) 2. Gas diffusion: • across membranes between alveolar air spaces and alveoalar capillaries, and across capillary walls between blood and other tissues

  13. 3 Processes of External Respiration • Transport of O2 and CO2: • between alveolar capillaries and capillary beds in other tissues

  14. What physical principles govern the movement of air into the lungs?

  15. Pulmonary Ventilation • Is the physical movement of air in and out of respiratory tract • Provides alveolar ventilation(movement of air into and out of the alveoli) • Alveolar ventilation: prevents the buildup of carbon dioxide in the alveoli and ensures a continuous supply of oxygen

  16. Atmospheric Pressure • The weight of air: • has several important physiological effects

  17. Gas Pressure and Volume • At normal atmospheric pressures, gas molecules are much farther apart than the molecules in a liquid, so the density of the air is relatively low. • The forces acting between gas molecules are minimal so an applied pressure can push them closer together.

  18. Gas Pressure and Volume Figure 23–13

  19. Boyle’s Law • Defines the relationship between gas pressure and volume: P = 1/V • In a contained gas: • external pressure forces molecules closer together • movement of gas molecules exerts pressure on container

  20. Mechanisms of Pulmonary Ventilation

  21. Pressure Difference • Air flows from area of higher pressure to area of lower pressure

  22. A Respiratory Cycle • Consists of: • an inspiration (inhalation) • an expiration (exhalation)

  23. Respiration • Causes volume changes that create changes in pressure • Volume of thoracic cavity changes: • with expansion or contraction of diaphragm or rib cage

  24. Compliance of the Lung • An indicator of expandability • Low compliance requires greater force • High compliance requires less force

  25. Factors That Affect Compliance • Connective-tissue structure of the lungs • Level of surfactant production • Mobility of the thoracic cage

  26. Compliance of the lung • Loss of supporting connective structure of the lung increases compliance (emphysema): easier to expand the lungs, although respiratory exchange surfaces are damaged • Inadequate surfactant decreases compliance (respiratory distress syndrome, skeletal muscle disorders): more pressure of force required to fill the lungs

  27. Gas Pressure • Can be measured inside or outside the lungs • Normal atmospheric pressure: • 1 atm or Patm at sea level: 760 mm Hg

  28. Pressure and Volume Changes with Inhalation and Exhalation Figure 23–15

  29. Intrapulmonary Pressure • Also called intra-alveolar pressure • Pressure inside the respiratory tract at the alveoli • Is relative to Patm • In relaxed breathing, the difference between Patm and intrapulmonary pressure is small: • about —1 mm Hg on inhalation or +1 mm Hg on expiration

  30. Maximum Intrapulmonary Pressure • Maximum straining, a dangerous activity, can increase range: • from —30 mm Hg to +100 mm Hg

  31. Intrapleural Pressure • Pressure in space between parietal and visceral pleura • Averages —4 mm Hg • Maximum of —18 mm Hg • Remains belowPatm throughout respiratory cycle due to the relationship between the lungs and the body wall. The elastic fibers continuously oppose the fluid bond and pull the lungs away from the chest wall and diaphragm, lowering the atmospheric pressure.

  32. The Respiratory Pump • Cyclical changes in intrapleural pressure operate the respiratory pump: • which aids in venous return to heart * On inspiration, diaphragm lowers, raising pressure in abdomen and lowers pressure in thorax, which creates partial vacuum in thorax that favors venous return to right atrium.

  33. Tidal Volume • Amount of air moved in and out of lungs in a single respiratory cycle • Average value: 500 cc

  34. What are the origins and actions of the respiratory muscles responsible for respiratory movements?

  35. The Respiratory Muscles Figure 23–16a, b

  36. The Respiratory Muscles Figure 23–16c, d

  37. The Respiratory Muscles • Most important are: • the diaphragm • external intracostal muscles of the ribs • accessory respiratory muscles : activated when respiration increases significantly

  38. The Mechanics of Breathing • Inhalation: • always active • Exhalation: • active or passive

  39. 3 Muscle Groups of Inhalation • Diaphragm: • contraction draws air into lungs • 75% of normal air movement

  40. 3 Muscle Groups of Inhalation • External intracostal muscles: • assist inhalation • 25% of normal air movement

  41. 3 Muscle Groups of Inhalation • Accessory muscles assist in elevating ribs: • sternocleidomastoid • serratus anterior • pectoralis minor • scalene muscles • internal intercostals • external and internal oblique • rectus abdominis

  42. Muscles of Active Exhalation • Internal intercostal and transversus thoracis muscles: • depress the ribs • Abdominal muscles: • compress the abdomen • force diaphragm upward

  43. Modes of Breathing • Respiratory movements are classified: • by pattern of muscle activity • into quiet breathing and forced breathing

  44. Quiet Breathing (Eupnea) • Involves active inhalation and passive exhalation • Diaphragmatic breathing or deep breathing: is dominated by diaphragm • Costal breathing or shallow breathing: is dominated by ribcage movements

  45. Elastic Rebound • When inhalation muscles relax: • elastic components of muscles and lungs recoil • returning lungs and alveoli to original position

  46. Forced Breathing • Also called hyperpnea • Involves active inhalation and exhalation • Assisted by accessory muscles • Maximum levels occur in exhaustion

  47. Respiratory Rates and Volumes • Respiratory system adapts to changing oxygen demands by varying: • the number of breaths per minute (respiratoryrate); adult: 12-18/min; children: 18-20/min • the volume of air moved per breath (tidal volume)

  48. Respiratory Minute Volume(VE) • Amount of air moved per minute • Is calculated by: respiratory rate (f)  tidal volume (VT) (normal: 6 L/min) • Measures pulmonary ventilation (how much air is moving into and out of the respiratory tract)

  49. Anatomic Dead Space(VD) • Only a part of respiratory minute volume reaches alveolar exchange surfaces • Volume of air remaining in conducting passages is anatomic dead space

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