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PHYSIOLOGY

PHYSIOLOGY. EXTERNAL AND INTERNAL RESPIRATION. EXTERNAL RESPIRATION. Respiration. Movement of gases between the environment and the body ’ s cells The exchange of air between the atmosphere and the lungs Known as ventilation or breathing Inspiration and Expiration

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PHYSIOLOGY

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  1. PHYSIOLOGY EXTERNAL AND INTERNAL RESPIRATION

  2. EXTERNAL RESPIRATION

  3. Respiration • Movement of gases between the environment and the body’s cells • The exchange of air between the atmosphere and the lungs • Known as ventilation or breathing • Inspiration and Expiration • The exchanges of O2 and CO2 between the lungs and the blood • Transport of O2 and CO2 by the blood • The exchange of gases between blood and the cells

  4. RESPIRATION

  5. Anatomy of the Respiratory System • Nasal Concha • Air eddies • Air is cleaned • Warmed • Humidified • Tonsils and Adenoids • Lymph nodes that filter the air • Located in the nose, back of the throat, below the tongue

  6. Larynx • Contains Vocal Cords • Connective tissue bands that tighten to create sound when air moves past them • Thyroid Cartilage • Sensitive to Testosterone levels

  7. Trachea • Conducts Air • Lined with pseudostratified ciliated columnar epithelium • Cilia can be paralyzed by cigarette smoke • Surrounded by C-shaped Cartilagenous rings and the trachealis muscle • Esophagus is dorsal to the trachea • Approximately 4 inches long

  8. The nose serves all the following functions except • As a passageway for air movement • As the initiator of the cough reflex • Warming and humidifying the air • Cleansing the air

  9. Conducting System or Respiratory Tree • Primary Bronchi • Surrounded by O-shaped cartilagenous rings • Bifurcates to Secondary Bronchi in the lungs • Respiratory Bronchioles • Surrounded by smooth muscles • Diameter of the airways becomes progressively smaller from the trachea to the bronchioles • The total cross-sectional area increases with each division of the airways

  10. Pleural Membranes • Visceral Pleura • Attached directly to the lungs • Parietal Pleura • Attaches to the visceral pleura • Also attaches to the thoracic cavity • Serous Fluid • Separates the two pleura and lubricates in order to decrease friction • Consistency of egg whites • Pleurisy occurs when the fluid decreases • The Function of the Pleural Membranes is to hold the lungs open

  11. Alveoli • Clustered at the ends of the terminal bronchioles • Makes up the bulk of lung tissue • Primary function is the exchange of gases between themselves and the blood • Surrounded by elastic fibers • Creates Elastic Recoil

  12. Capillaries • The alveoli are closely associated with an extensive network of capillaries • Blood vessels cover 80-90% of the alveolar surface forming a continuous “sheet” of blood in close contact with the air-filled alveoli

  13. Respiratory Membrane • Consists of • The Wall of the Alveoli • The Respiratory Space • This is a fluid filled space • Pneumonia may cause the space to fill with more fluid than normal • This decreases the ability to exchange gases • The Wall of the Capillary

  14. Surfactant helps to prevent the alveoli from collapsing by • Humidifying the air before it enters • Warming the air before it enters • Interfering with the cohesiveness of water molecules, thereby reducing the surface tension of alveolar fluid • Protecting the surface of alveoli from dehydration and other environment variations

  15. The respiratory membrane is a combination of • Respiratory bronchioles and alveolar ducts • Alveolar walls, alveolar space and capillary walls • Atria and alveolar sacs • None of the above

  16. Gas Laws • At sea level normal atmospheric pressure is 760mmHg • On top of Mt. Everest Patm = 153mmHg

  17. Dalton’s Law • The total pressure exerted by a mixture of gases is the sum of the pressures exerted by the individual gases • 78% N2 • 21% O2 • 1% CO2 • Partial Pressure of gases • The pressure of a single gas in a mixture

  18. Gas Law • The total pressure of a mixture of gases, is the sum of the pressures of the individual gases (Dalton’s Law) • Gases, singly or in a mixture, move from areas of higher pressure to areas of lower pressure • If the volume of a container of gas changes, the pressure of the gas will change in an inverse manner (Boyle’s Law)

  19. Dalton’s Law • To find the partial pressure of any one gas in a sample of air, multiply the atmospheric Pressure (Patm) by the gas’s relative contribution (%) to Patm. • Partial pressure of an atmospheric gas = • Patm X % of gas in atmosphere • Partial pressure of oxygen = 760mmHg X 21% • PO2 = 760 X 0.21 = 160mmHg

  20. Gases Move from High Pressure to Low Pressure • Air flow occurs whenever there is a pressure gradient

  21. Boyle’s Law • The pressure exerted by a gas or mixture of gases in a sealed container is created by the collisions of moving gas molecules with the walls of the container and with each other. • P1V1 = P2V2 • An increase in volume will create a decrease in pressure and a decrease in volume will create an increase in pressure

  22. Boyle’s Law • Changes in the volume of the chest cavity during ventilation cause pressure gradients that create air flow • When the chest volume increases, the alveolar pressure falls, and air flows into the respiratory system • When the chest volume decreases, the alveolar pressure rises, and air flows out into the atmosphere

  23. Alveoli • Composed of a single layer of epithelium called Type I cells • Type II alveolar cells • Secretes surfactant • Surfactant decreases the surface tension of the water within the alveoli • Coats the inside of the alveoli • Cortisol causes the maturation of the type II cells in the fetal stage of development • Dust Cells • Phagocytes

  24. Law of LaPlace • The pressure inside a bubble formed by a fluid film is a function of two factors • Surface tension of the fluid (T) • Radius of the bubble (r) • P = 2T/r • Surfactant decreases the surface tension of water in the alveoli • Newborn Respiratory Distress Syndrome (RDS)

  25. Air Flow • Flow = changes in P / R • P = Pressure • R = Resistance to Flow • Air flow in response to a pressure gradient • The flow decreases as the resistance to flow increases

  26. Pressure in the System • Alveolar Pressure • Pressure in the air spaces of the lungs • Intrapleural Pressure • Pressure in the pleural fluid • Intrapulmonary Pressure • Pressure within the lungs as a whole • Atmospheric Pressure • Pressure in the atmosphere due to a column of air up to the stratosphere

  27. The pleurae are vital to the integrity of the lungs because they • Contain cilia that protect the lungs • control the volume of the lungs • Secrete a lubricating serous fluid, allowing the lungs to glide over the thoracic wall during breathing • Maintain the proper temperature of the lungs during sleep

  28. The factor(s) responsible for holding the lungs to the thoracic wall is/are • The smooth muscles of the lung • The diaphragm and the intercostals muscles • The visceral pleurae and the changing volume of the lungs • Surface tension from pleural fluid, positive pressure, and atmospheric pressure on the thorax

  29. Inspiration • Time 0. • In the brief pause between breathes, alveolar pressure is equal to atmospheric pressure • When pressures are equal, there is no air flow • Time 0-2 sec • Oxygen levels fall and Carbon Dioxide levels rise • Peripheral Chemoreceptors are stimulated • Located in the carotid arteries • Sensitive to oxygen levels • Central Chemoreceptors are stimulated • Located in the Medulla Oblongata of the brain • Sensitive ot carbon dioxide levels

  30. Inspiration • Chemoreceptors stimulate the Medulla Oblongata • The MO stimulates the Phrenic Nerve • The Phrenic Nerve stimulates the respiratory muscles of the thoracic cage and the diaphragm • The muscles contract and the thoracic volume increases

  31. Inspiration • When thoracic volume increases then alveolar pressure fall approximately 4mmHg below atmospheric pressure • Air flows from high pressure to low pressure until the pressures reach equilibrium

  32. Exhalation • Time 2-4 sec: • As lung and thoracic volumes decrease air pressure in the lungs increases until the pressures equal equilibrium • Stretch receptors in the lung tissue are stimulated • Stretch receptors send information to the MO and this stops the phrenic nerve stimulation • Respiratory muscles relax • Time 4 sec: • Elastic Recoil occurs • Alveolar pressure is now higher than atmospheric pressure due to a decrease in lung volume • Air leaves the lungs until pressures reach equilibrium

  33. Intrapleural Pressure Changes During Ventilation • The lungs are “stuck” to the thoracic cage by the cohesive forces exerted by the fluid between the two pleural membranes • If the thoracic cage moves, the lungs move with it

  34. Intrapleural Pressure • The pressure between the pleural membranes is normally subatmospheric • The combination of the outward pull of the thoracic cage and in inward recoil of the elastic lungs creates a subatmospheric intrapleural pressure of about -3mmHg

  35. What happens to subatmospheric intrapleural pressure if an opening is made between the sealed pleural cavity and the atmosphere?

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