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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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