Gas Exchange

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

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

6. 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

7. 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

8. 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

9. trachea bronchi

10. 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

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

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

13. 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.

15. 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

16. 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

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

18. 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

20. 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

21. 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

23. 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

24. 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

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

27. 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

28. Internal respiration External respiration

29. 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

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

31. 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

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

33. 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