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Gas Exchange

Gas Exchange. Chapter 27. Pathway of Inhaled Air. Nasal Cavity. The cavity is lined with mucus and cilia to trap and remove particles from the air The moist surface of the nasal cavity moistens the air Blood in capillaries heat the air to body temperature

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Gas Exchange

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  1. Gas Exchange Chapter 27

  2. Pathway of Inhaled Air

  3. Nasal Cavity • The cavity is lined with mucus and cilia to trap and remove particles from the air • The moist surface of the nasal cavity moistens the air • Blood in capillaries heat the air to body temperature • Olfactory nerves detect odors in the inhaled air

  4. Pharynx • Junction for air and food • Epiglottis blocks the trachea during swallowing • Air is further moistened and warmed as it travels through the pharynx

  5. Larynx • Also known as the voice box • Triangular box made of cartilage with vocal cords stretched across • Tightening or loosening the vocal cords when air vibrates the cords produces sound

  6. Trachea • Also known as the windpipe • C-shaped cartilage rings reinforce and keep the airway open • Cilia and mucus in the trachea further clean inhaled air

  7. Bronchi • Branches from trachea to the right and left lung • Also lined with cilia and mucus, and contains cartilage rings • Branches further into smaller tubes called bronchioles (no cartilage or cilia) inside the lungs

  8. trachea bronchi

  9. Lungs • Contain 300 x 106 small air sacs called alveoli (100 m2) • Alveoli are surrounded by capillaries • Alveolar walls are thin and moist for gas exchange • Surfactants also prevent alveolar walls from collapsing

  10. Respiratory system (3.5 min): http://www.youtube.com/watch?v=hc1YtXc_84A

  11. Breathing • Inhalation brings O2 rich air into the body • Exhalation removes CO2 filled air from the body

  12. Control of breathing rate • Breathing is controlled by the respiratory center in the medulla oblongata • Breathing rate increases when there is increased [CO2] or [H+] in the blood • Chemoreceptors in the carotid arteries and aorta also monitor [CO2] and [O2] • Inhalation is actively controlled by the brain while exhalation is passively controlled.

  13. Inhalation • Stimulation of the intercostal muscles between the rib cage and the diaphragm causes them to contract • The ribs move upwards and outwards while the diaphragm contracts downward • The increased volume creates negative air pressure which sucks air into the lungs

  14. Exhalation • Stretch receptors on the alveolar walls detect the expansion of the alveoli • Intercostal muscles and diaphragm relax • Ribs move downward and inward while the diaphragm moves up • The decreased volume creates positive air pressure which forces air out of the lungs

  15. Breathing (2.5 min): http://www.youtube.com/watch?v=NSEzg6TBheY

  16. Gas exchange • External respiration is gas exchange between the alveoli and blood • Internal respiration is gas exchange between the body cells and blood • Gradients in partial pressure of CO2 (pCO2) and O2 (pO2) cause gas diffusion

  17. External Respiration • There is greater pO2 in the alveoli than in the surrounding blood, so O2 diffuses into the blood • There is greater pCO2 in the surrounding blood than the alveoli, so CO2 diffuses into the alveoli External respiration (2 min.) https://www.youtube.com/watch?v=AJpur6XUiq4

  18. Internal Respiration • There is greater pO2 in the surrounding blood than in the body cells, so O2 diffuses into the body cells • There is greater pCO2 in the body cells than the blood, so CO2 diffuses into the blood

  19. Hemoglobin • Globular pigmented protein containing 4 heme groups with Fe2+ in the center • Transports O2, CO2 or H+ • Its affinity for O2 is affected by pO2, temperature and pH

  20. Alveoli Body cells pO2 104 mm Hg 40 mm Hg pH 7.40 7.38 Temperature 37 ◦C 38 ◦C Result on hemoglobin Picks up O2 HbO2 Releases O2 Hb + O2

  21. Partial Pressure and Hemoglobin (10 min): https://www.youtube.com/watch?v=Cqt4LjHnMEA

  22. Transport of CO2 • Dissolved as CO2 gas in the plasma • Picked up by hemoglobin as Carboaminohemoglobin (HbCO2) • Dissolved as bicarbonate ions (HCO3-) CO2 transport (3 min): https://www.youtube.com/watch?v=x26TWL3VKMg

  23. Internal respiration External respiration

  24. Fetal Respiration • Gas exchange occurs in the placenta where fetal and maternal capillaries lie close together • Fetal hemoglobin has a higher affinity for O2 and pulls O2 from the mother’s blood • Fetal CO2 is picked up by maternal blood and exhaled by the mother • At birth, the rise in CO2 and H+ in fetal circulation causes the baby to take its first breath

  25. Fetal circulation: https://www.youtube.com/watch?v=zvNPw7m74HE

  26. Effects of Smoking • The cilia and mucus of the respiratory tract are not adequate to clean the particulate matter in cigarette smoke • Pollutants and carcinogens enter the lung, damaging the alveoli and reducing gas exchange efficiency • Continual irritation and inflammation of the lungs lead to Chronic Obstructive Pulmonary Diseases (COPD) Impacts of smoking (4 min): https://www.youtube.com/watch?v=oW45KJMuEhI

  27. Chronic bronchitis: bronchioles are inflamed and have increased mucus Emphysema: alveoli are damaged and there is a decrease in surface area for gas exchange

  28. COPD Symptoms • a cough that lasts a long time, or coughing up "stuff" (mucus) • feeling short of breath, especially when you are making an effort (climbing stairs, exercising) • many lung infections that last a long time (the flu, acute bronchitis, pneumonia, etc.) • wheezing (a whistling sound when you breathe) • feeling tired (fatigue) • losing weight without trying COPD (3 min): https://www.youtube.com/watch?v=aktIMBQSXMo

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