1 / 67

Gas Exchange Part I

Gas Exchange Part I. Respiration – taking up O 2 giving up CO 2 Photosynthesis – taking up CO 2 , giving up O 2. Respiratory medium (air or water). Respiratory surface. O 2. CO 2. Organismal level. Circulatory system. Cellular level. Energy-rich fuel molecules from food. ATP.

fai
Télécharger la présentation

Gas Exchange Part I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Gas Exchange Part I

  2. Respiration – taking up O2 giving up CO2 Photosynthesis – taking up CO2, giving up O2.

  3. Respiratory medium (air or water) Respiratory surface O2 CO2 Organismal level Circulatory system Cellular level Energy-rich fuel molecules from food ATP Cellular respiration

  4. What is diffusion? epswww.unm.edu/.../eps462/graphics/diffusion.gif

  5. Depends on • partial pressure, • surface area • A gas always diffuses from an area of high partial pressure to low partial pressure. • What is equilibrium?

  6. Partial pressure of gases: pressure exerted by a particular gas in a mixture of gases. We need to know: • Pressure that is exerted by mixture • Fraction of mixture represented by the particular gas • Atmosphere is 21% by volume O2. At sea level atmospheric pressure is 760mm Hg. • PO2 is 760mm Hg X 0.21 = 160mm Hg

  7. What happens in water? • Amount of gas dissolved in water is proportional to • partial pressure in air • solubility in water.

  8. At equilibrium partial pressure of a gas in air (PO2 of 160mm Hg) = partial pressure of that gas in solution (PO2 of 160mm Hg) • Concentration of a gas depends on the solubility of the gas. • Solubility decreases with increase of temperature and dissolved solids. • Concentration of O2 [O2] is about 40 times more in air than water.

  9. Comparison of the two respiratory media:

  10. Aquatic animals have had to evolve very effective and efficient gas exchange strategies.

  11. Respiratory surfaces are plasma membranes which must be moist. Gas exchange takes place by diffusion. • Rate of diffusion is • directly proportional to the surface area across which it occurs • inversely proportional to the square of the distance the molecules have to travel. • To speed up the rate of diffusion, respiratory surfaces have to be LARGE and THIN.

  12. In unicellular and simple animals diffusion occurs between all cells and environment.

  13. LE 42-3 • If body surface is enough then skin can be a respiratory organ. • Earthworm – surface is moist, supplied richly by capillaries Dorsal vessel (main heart) Auxiliary hearts Ventral vessels A closed circulatory system.

  14. If body surface area is insufficient – need for specialized respiratory organs • Larger animals have respiratory organs consisting of respiratory surfaces and other structures. • Size of respiratory surface depends on • Size of organism • Metabolic demands

  15. To accommodate large respiratory surfaces inside the body – • Folded • Branced • Examples: gills, trachea, lungs

  16. Gills: outfoldings of the body that are suspended in water; surface area much larger than the rest of the body. • There are a large variety of gills

  17. Parapodia Gill Marine Worm Marine worm

  18. LE 42-20d Gills Crayfish Crayfish

  19. LE 42-20a Gills Coelom Tube foot Sea Star Sea star

  20. Oxygen-poor blood Lamella Oxygen-rich blood Gill arch Blood vessel Gill arch 15% 40% 70% Water flow 5% 30% Operculum 60% 100% 90% Water flow over lamellae showing % O2 O2 Blood flow through capillaries in lamellae showing % O2 Gill filaments Countercurrent exchange

  21. Ventilation: movement of respiratory medium over respiratory surface. • Promoted by • moving the gills • moving water over the gills • swimming

  22. Countercurrent exchange: exchange of substance between two fluids (blood and water) flowing in opposite directions and thereby maximizing gas exchange efficiency (about 80%)

  23. Gills are unsuitable for land: • water supports the filaments and keep them separate • gills would dry up

  24. Tracheal systems: Most common respiratory structure. Consists of: • Large tubes (trachea – supported by chitin rings) branch into… • Smaller tubes, tracheoles (fluid at terminal end); bring enough O2 to the tissues and removes enough CO2 from the tissues. • Air sacs: supply air to organs with higher O2 needs. Tracheae Air sacs Spiracle

  25. Body cell Air sac Tracheole Trachea Air Body wall Mitochondria Tracheoles Myofibrils 2.5 µm

  26. O2 demand can go up during flight by up to 200X. • The demand is met by: • Contraction and relaxation of the flight muscles pumps air through the tracheal system • Flight muscles rich in mitochondria. • Withdrawal of fluid from tracheole into body increases surface area.

  27. Lungs: • localized respiratory organs; • inflodings of the body surface separated consisting of numerous small pockets. • Circulatory system transports O2 to the body from the lungs and CO2 from the body to the lungs

  28. Most reptiles, all birds and mammals use lungs for gas exchange • Amphibians and some reptiles (turtles) supplement lungs with parts of their skin. • Some aquatic animals (lungfishes) use lungs for gas exchange

  29. For animals with gills or lungs – endotherms have greater surface area than ectotherms.

  30. Gas Exchange Part II

  31. Pathway of air to the gas exchange surface in mammals: Nasal cavity Pharynx Larynx Glottis (covered by epiglottis during swallowing) Trachea Bronchi Bronchioles Alveoli Nasal cavity Pharynx Larynx Esophagus Left lung Trachea Right lung Bronchus Bronchiole Diaphragm Heart

  32. Mucus traps dust, beating cilia move the mucus to esophagus • Millions of alveoli in lungs, total area about 100 m2.

  33. Branch from pulmonary artery (oxygen-poor blood) Branch from pulmonary vein (oxygen-rich blood) • Alveoli are surrounded by capillaries. • Surface is coated by moist fluid that helps in gas exchange. • Surfactants keep alveoli from collapsing. Terminal bronchiole Alveoli 50 µm 50 µm Colorized SEM SEM

  34. Breathing: process to ventilate lungs. • Amphibian breathing: positive airflow. • Mammalian breathing: negative pressure breathing.

  35. Mammalian breathing • During inhalation - expand thoracic cavity, causes lower air pressure in thoracic chamber, air rushes in; opposite process for exhalation. • Rib muscles, diaphragm, double layered membrane between lungs and thoracic cavity participate. • During exercise muscles of neck, back and chest are also involved.

  36. LE 42-24 Rib cage gets smaller as rib muscles relax Rib cage expands as rib muscles contract Air inhaled Air exhaled Lung Diaphragm EXHALATION Diaphragm relaxes (moves up) INHALATION Diaphragm contracts (moves down)

  37. Tidal volume: volume of air inhaled and exhaled at each breath (~ 500ml) • Vital capacity: • maximum volume of air that a person can exhale after maximum inhalation, OR • maximum volume of air that a person can inhale after maximum exhalation. 3.4L in college age women, 4.8L in college age men. • decreases with age. • Residual volume: Air that remains after forced exhalation.

  38. Avian breathing: • Ventilation is more efficient and more complex. • Maximum PO2 is higher than that of mammals. • Birds are better adapted to higher altitudes than humans.

  39. Airflow over gas exchange surface is in one direction only • No mixing of fresh and used air. • 8 – 9 pairs of air sacs that act as bellows. • Parabronchi in the lungs, no alveoli • 2 sets of inhalation and exhalation are needed to completely pass air through the system.

  40. LE 42-25 Air Air Anterior air sacs Trachea Posterior air sacs Lungs Lungs Air tubes (parabronchi) in lung 1 mm INHALATION Air sacs fill EXHALATION Air sacs empty; lungs fill

  41. Breathing is controlled (involuntarily) to ensure • Gas exchange coordinates with circulation • Metabolic needs are met

  42. Cerebrospinal fluid • Breathing is controlled by two regions at the base of the brain – pons and medulla oblongata Pons Breathing control centers Medulla oblongata

  43. During respiration cells produce CO2. • CO2 concentration in blood goes up. • CO2 diffuses from blood to cerebrospinal fluid (CSF).

  44. In CSF CO2 + H2O H2CO3 HCO3- + H+

  45. Increased metabolic activity (exercise) – [CO2] increases • Results in increase in [H+] • Results in decrease in pH.

  46. pH in CSF is an indicator of blood [CO2]. • Decrease in pH is an indicator of increased [CO2] • Decreased pH in cerebropspinal fluid results in control centers of the brain increasing the rate and depth of breathing. • When CO2 is exhaled, pH increases and breathing is returned to normal.

  47. Cerebrospinal fluid Pons Breathing control centers Medulla oblongata Carotid arteries Aorta Diaphragm Rib muscles

  48. CO2 concentration is primarily used to control breathing • O2 concentration influences breathing only when it is very low. • Aorta and carotid arteries have O2 sensors which signal the brain ti increases breathing • Increased breathing is always coupled with increased cardiac output.

  49. Coordination of circulation and gas exchange.

More Related