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2. Immagini e concetti della biologia Sylvia S. Mader
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

3. C7 - Respiratory system
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

4. Gas exchange Respiration involves various processes:
Ventilation - breathing
External respiration - gas exchange between the air and the blood in the lungs
Internal respiration - gas exchange between the blood and the tissue fluid
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

5. Gas exchange Gas exchange needs moist respiratory surfaces to occur.
Aquatic organisms spend up to 25% of the energies to extract air from water.
Terrestrial organisms need to moisten constantly the respiratory surfaces.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

6. Direct respiration through surfaces
Small aquatic animals as cnidarians and plathelminthes exchange gases directly with the external environment.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

7. Branchial respiration
Aquatic invertebrates (mollusks and crustacean) and vertebrates (fish) have specialized organs for gas exchange called gills.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

8. Direct respiration through canals
Insects use tracheae to deliver oxygen directly to muscles.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

9. Direct respiration through canals
Terrestrial vertebrates and marine mammals usually moist air before it enters the lungs.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

10. Countercurrent exchange
Gills
Water moves across the gills near the mouth. Fish use countercurrent exchange to transfer oxygen efficiently to blood.
Countercurrent exchange
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

11. Lungs
The respiratory system includes all structures that bring air to the lungs.
The air is warmed and humidified in the nasal cavity and mouth.
The glottis opens and the trachea connects the larynx to the two bronchi.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

12. Bronchioles and alveoli
Bronchi branch into bronchioles that end in alveoli. Alveoli compose the lung and are the site for gas exchange with blood.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

13. Smoking is dangerous
Short-term effects: nagging cough, diminished sense of smell, premature aging of the skin.
Long-term effects: cancer, heart diseases, aneurysm, pulmonary diseases, stroke.
Other effects: chance of premature birth, low birth weight and stillbirth.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

14. Inspiration and expiration
Inspiration consists of muscle contractions that lower the diaphragm and raise the ribs. The negative pressure causes the air to flow in.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

15. Inspiration and expiration
During expiration the diaphragm muscles relax and air flows out as the inner pressure increases.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

16. Respiratory centers
Breathing rhythms are automatically controlled by the respiratory center located in the medulla oblongata, in the lowermost part of the brain stem.
Changing in blood pH can cause variation in the respiration speed rate.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

17. Respiration and physical exercise
During exercise the respiratory system makes adjustments in response to the duration and intensity of the effort.
During exercises the amount of O2 needed and CO2 produced increase. Consequently the blood flow in both muscles and lungs must also increase.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

18. External and internal respiration
External and internal respiration take advantage from the spontaneous gas diffusion between air and blood.
In the lungs the oxygen partial pressure (PO2) is higher while PCO2 is lower than in the blood.
Hence CO2 diffuses out of the blood into the lungs and O2 diffuses out of the lungs into the blood.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

19. Hemoglobin
Hemoglobin (Hb) is a red blood cells protein involved in the transport of gases.
External respiration
Hb combines with O2 to form HbO2.
HCO3- forms H2CO3 which breaks down into H2O and CO2.
Internal respiration
HbO2 releases O2 into cells.
Hb combines with CO2.
CO2 combines with water to form H2CO3 which then becomes HCO3-.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

20. External and internal respiration
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018