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Gas Exchange: Respiration

Gas Exchange: Respiration. Respiratory medium (air of water). O 2. CO 2. Respiratory surface. Organismal level. Circulatory system. Cellular level. Energy-rich molecules from food. ATP. Cellular respiration. Figure 42.19. Gas exchange occurs across specialized respiratory surfaces

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Gas Exchange: Respiration

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  1. Gas Exchange: Respiration

  2. Respiratorymedium(air of water) O2 CO2 Respiratorysurface Organismal level Circulatory system Cellular level Energy-richmoleculesfrom food ATP Cellular respiration Figure 42.19 • Gas exchange occurs across specialized respiratory surfaces • Gas exchange • Supplies oxygen for cellular respiration and disposes of carbon dioxide

  3. Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases • Between their cells and the respiratory medium, either air or water

  4. In mammals, air inhaled through the nostrils • Passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs

  5. Gas exchange: occurs in alveoli of lungs, diffusion of oxygen and carbon dioxide through capillaries • Ventilation: bringing in fresh air into the alveoli (breathing) • Cellular respiration: produces ATP for the cell, uses oxygen and produces carbon dioxide.

  6. Branch from thepulmonaryartery(oxygen-poor blood) Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasalcavity Alveoli Pharynx Left lung Esophagus Larynx 50 µm Trachea 50 µm Right lung Bronchus Bronchiole Colorized SEM SEM Diaphragm Heart Figure 42.23 Mammalian Respiratory Systems: A Closer Look • A system of branching ducts • Conveys air to the lungs

  7. Alveoli • Very small but huge in numbers (large surface area for gas exchange) • Made up of a single layer of thin cells • Covered by a dense network of blood capillaries

  8. Rib cage expands asrib muscles contract Rib cage gets smaller asrib muscles relax Air inhaled Air exhaled Lung Diaphragm INHALATIONDiaphragm contracts(moves down) EXHALATIONDiaphragm relaxes(moves up) Figure 42.24 How a Mammal Breathes • Mammals ventilate their lungs by breathing • By negative pressure breathing, which pulls air into the lungs

  9. Inhalation: • External intercostal muscles contract (moves rib cage up and out) • Diaphragm contracts • Increase in volume, drop in pressure (below atmospheric pressure) • Air flows into lungs until pressure inside lungs rises to atmospheric pressure.

  10. Exhalation • Internal intercostal muscles contract (moves rib cage down and in) • Abdominal muscles contract, pushing up diaphragm • Decrease in volume, pressure rises above atmospheric pressure • Air flows out of lungs until the pressure in lungs falls back to atmospheric pressure.

  11. Why do we need a ventilation system??? • Maintain the concentration gradients of gases (oxygen/carbon dioxide) in the alveoli. • Carbon dioxide needs to be low in alveoli so it moves into the alveoli from capillaries. • Oxygen needs to be high in alveoli so it can move into capillaries. • Ventilation makes this possible by getting rid of carbon dioxide and bringing in oxygen

  12. The Role of Partial Pressure Gradients • Gases diffuse down pressure gradients • In the lungs and other organs • Diffusion of a gas • Depends on differences in a quantity called partial pressure • A gas always diffuses from a region of higher partial pressure • To a region of lower partial pressure

  13. In the lungs and in the tissues • O2 and CO2 diffuse from where their partial pressures are higher to where they are lower • RESPIRATION

  14. Inhaled air Exhaled air 120 27 160 0.2 Alveolar spaces O2 CO2 O2 CO2 Alveolarepithelialcells 104 40 O2 CO2 O2 CO2 Blood leaving alveolar capillaries Blood enteringalveolarcapillaries O2 CO2 3 1 2 4 Alveolar capillariesof lung 40 45 104 40 O2 O2 CO2 CO2 Pulmonaryveins Pulmonaryarteries Systemic arteries Systemicveins Heart Tissue capillaries O2 CO2 Blood enteringtissuecapillaries Blood leavingtissuecapillaries O2 CO2 100 40 40 45 O2 O2 CO2 CO2 Tissue cells <40 >45 O2 CO2 Figure 42.27

  15. Respiratory Pigments • Respiratory pigments • Are proteins that transport oxygen • Greatly increase the amount of oxygen that blood can carry • The respiratory pigment of almost all vertebrates • Is the protein hemoglobin, contained in the erythrocytes

  16. Heme group Iron atom O2 loaded in lungs O2 O2 unloaded In tissues O2 Polypeptide chain • Like all respiratory pigments • Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body Figure 42.28

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