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The Mechanics of Breathing

The Mechanics of Breathing. Breathing. The mechanism by which mammals ventilate their lungs Air will flow from a region of higher pressure to a region of lower pressure There are two muscular structures that control air pressure inside our lungs. Muscles involved in breathing:.

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The Mechanics of Breathing

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  1. The Mechanics of Breathing

  2. Breathing • The mechanism by which mammals ventilate their lungs • Air will flow from a region of higher pressure to a region of lower pressure • There are two muscular structures that control air pressure inside our lungs

  3. Muscles involved in breathing:

  4. Intercostal Muscles

  5. Intercostal Muscles

  6. Intercostal Muscles

  7. X-Section of Intercostal Muscles

  8. Diaphragm • A muscle layer that separates • the thoracic cavity (region of the lungs) from • the abdominal cavity (region of the stomach and the liver)

  9. Diaphragm

  10. How breathing works Lungs Diaphragm Inhalation vs. Exhalation Diaphragm

  11. HOW BREATHING WORKS- Inhalation • To inhale, the external intercostal muscles contract • Intercostal muscles expand the rib cage, lifting it up and out

  12. HOW BREATHING WORKS- Inhalation • the diaphragm contracts and pulls downward in the thoracic cavity • This increases the volume of the thoracic cavity, causing the lungs to expand. • How?

  13. How Lungs Expand • The thoracic cavity is relatively airtight • An increase in its volume, produces a decrease in air pressure within the cavity • This decrease in pressure draws the flexible walls of the lungs outward into the thoracic cavity • Therefore, the lungs expand

  14. HOW BREATHING WORKS- Inhalation • As a result of this expansion, the air pressure within the lungs is lower than the air pressure in the external environment • Recall: Air will flow from a region of higher pressure to a region of lower pressure • Therefore, air enters thelungs

  15. HOW BREATHING WORKS- Exhalation • The diaphragm relaxes, returning to a dome-shaped curve

  16. HOW BREATHING WORKS- Exhalation • To exhale, the external intercostal muscles relax • But the internal intercostal muscles contract to help pull the ribcage back to its original shape and position

  17. HOW BREATHING WORKS- Exhalation • These changes create a higher pressure in the thoracic cavity • This causes the lungs to shrink, which resultsin a higher pressurein the lungs • Air then moves outthrough the trachea

  18. Inhalation and Exhalation • Intercostal muscles contract, lifting rib cage up and out • Diaphragm contracts and pulls downward • The lungs expand, air is sucked in • Intercostal muscles relax • Diaphragm relaxes • The ribs fall downward and inward • Diaphragm back into dome shape, squeezing lungs and pushing air out

  19. Exchange of Gases • Review Capillary network and gas exchange

  20. Composition of inspired and expired air under normal conditions 16.49% Oxygen 4.49% Carbon Dioxide 79.02% Nitrogen and Trace gases 20.94% Oxygen 0.04% Carbon Dioxide 79.02% Nitrogen and Trace gases

  21. Lung Capacity • The different volumes of air drawn in or pushed out by the lungs are distinguished

  22. The volume of air inhaled and exhaled in a normal breathing movement

  23. The additional volume of air that can be taken in, beyond a regular or tidal inhalation

  24. The additional volume that can be forced out of the lungs, beyond a regular or tidal exhalation

  25. The total volume of gas that can be moved in or out of the lungs • VC=Tidal volume+IRV+ERV

  26. The amount of gas that remains in the lungs and the passageways of the respiratory system even after a full exhalation • The residual volume never leaves the respiratory system • If it did, the lungs and the respiratory passageways would collapse • It has little value for gas exchange, because it is not exchanged with air from the external environment

  27. Respiratory Efficiency • In mammals, the rate at which oxygen can be transferred into the blood stream for transport to the rest of the body • There are factors that affect the respiratory efficiency • Other animals have respiratory systems with special adaptations to help increase respiratory efficiency • One adaptation is facilitated diffusion

  28. The Respiratory System in Fish • The gills of fish utilize counter-current flow • A very effective mechanism for removing the maximum amount of oxygen from the water flowing over them

  29. Oxygenated blood Gills & Gas Exchange: Counter-current Flow Deoxygenated Blood • During counter-current flow, two types of fluids (blood and water) with different concentrations flow in opposite directions past one another

  30. Counter-current Flow • These two fluids (water and blood) are separated by thin membranes

  31. Counter-current Flow Filament • Fish gills consist of a series of filaments supported by bony gill arches • Each filament is covered with thin folds of tissue called lamella • Blood flows across each lamella within a dense network of capillaries Gill arch Gill arch High O2 Filament Lamellae Low O2

  32. Counter-current Flow • Water is deflected over the lamellae in a direction opposite the flow of blood in the capillaries • Thus, the most highly oxygenated blood is brought close to the water that is just entering the gills and that has an even higher oxygen content than blood Vein-Oxygen poor blood Artery-Oxygen rich blood Low Oxygen High Oxygen Water flow Low Oxygen High Oxygen Blood flow

  33. Counter-current Flow • As the water flows over the lamellae, gradually losing its oxygen to the blood, it encounters blood that is also increasingly low in oxygen • In this way, the gradient encouraging oxygen to move from the water into the blood is maintained across all the lamellae. Vein-Oxygen poor blood Artery-Oxygen rich blood Low Oxygen High Oxygen Water flow Low Oxygen High Oxygen Blood flow

  34. Counter-current Flow Vein-Oxygen poor blood Artery-Oxygen rich blood Low Oxygen High Oxygen Water flow Low Oxygen High Oxygen Blood flow

  35. Current vs. Counter-current Flow

  36. Counter-current Flow • Within each lamella, Counter-current flow enhances diffusion by maintaining a concentration gradient of oxygen between the water (relatively high in oxygen) and the blood (lower in oxygen) • Countercurrent flow is so effective that some fish extract 85% of the oxygen from the water that flows over their gills.

  37. Gas Exchange in Mammals • In the mammalian lung, the oxygen gradient between the respiratory medium in the lungs and the blood in the capillaries is steadily reduced as oxygen passes across the alveoli wall • The blood may take up about 50% of the oxygen in the respiratory medium entering the lungs

  38. Gas Exchange in Fish • In a countercurrent exchange system, the oxygen gradient is maintained over the whole of the gill • The blood may take up as much as 80% of the oxygen carried in the respiratory medium entering the gill

  39. The Respiratory System in Birds • Respiration in birds is much different than in mammals. • Birds do not have a diaphragm; instead, air is moved in and out of the respiratory system through pressure changes in the air sacs

  40. Avian Respiratory System Anterior air sacs • Inhalation: • When the bird breathes in, the airsacs expand • Most of the inhaled air passes intothe posterior air sacs • Some flow from there into the lungs • At the same time, the airthat was in the lungsmoves into the anteriorair sacs Posterior air sacs Anterior air sacs Lungs

  41. Avian Respiratory System Anterior air sacs • Exhalation: • When the bird exhales, all the airsacs contract, forcing the air in theposterior air sacs into the capillary-lined tubes of the lungs • Gas exchange takes place in the lungs • Then, the air from the anterior air sacsis forced out throughthe trachea Posterior air sacs Anterior air sacs Lungs

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