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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. 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

  9. 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

  10. 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

  11. 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

  12. 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

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

  14. 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

  15. 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)

  16. 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

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

  18. 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

  19. 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

  20. 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

  21. 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)

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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

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

  31. A knifing? • Air in the pleural cavity breaks the fluid bond holding the lung to the chest wall • The chest wall expands outward while the elastic lung collapses to an unstretched state • Like a deflated balloon • Pneumothorax • Results in a collapsed lung that is unable to function normally • Correction of a Pneumothorax • Removing as much air from the pleural cavity as possible with a suction pum • Sealing the hole

  32. Emphysema • Loss of elastic fibers for elastic recoil during expiration • Elastin is destroyed by elastase • An enzyme released by immune cells • Have more difficulty exhaling than inhaling

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