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2 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sylvia S. Mader Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 C8 - Respiratory system

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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.

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Direct respiration through surfaces Small aquatic animals as cnidarians and plathelminthes exchange gases directly with the external environment.

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Branchial respiration Aquatic invertebrates (mollusks and crustacean) and vertebrates (fish) have specialized organs for gas exchange called gills.

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Direct respiration through canals Insects use tracheae to deliver oxygen directly to muscles.

9 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Direct respiration through canals Terrestrial vertebrates and marine mammals usually moist air before it enters the lungs.

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Gills Water moves across the gills near the mouth. Fish use countercurrent exchange to transfer oxygen efficiently to blood. Countercurrent exchange

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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.

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Bronchioles and alveoli Bronchi branch into bronchioles that end in alveoli. Alveoli compose the lung and are the site for gas exchange with blood.

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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.

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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.

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Inspiration and expiration During expiration the diaphragm muscles relax and air flows out as the inner pressure increases.

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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.

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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 O 2 needed and CO 2 produced increase. Consequently the blood flow in both muscles and lungs must also increase.

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 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 (P O 2 ) is higher while P CO 2 is lower than in the blood. Hence CO 2 diffuses out of the blood into the lungs and O 2 diffuses out of the lungs into the blood.

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Hemoglobin External respiration Hb combines with O 2 to form HbO 2. HCO 3 - forms H 2 CO 3 which breaks down into H 2 O and CO 2. Hemoglobin (Hb) is a red blood cells protein involved in the transport of gases. Internal respiration HbO 2 releases O 2 into cells. Hb combine with CO 2. CO 2 combine with water to form H 2 CO 3 which then becomes HCO 3 -.

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 External and internal respiration

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Respiratory disorders In restrictive pulmonary disorders, lung capacity is reduces as the lugs have lost their elasticity. In obstructive pulmonary disorders, air does not flow easily in the airways. Common types are bronchitis, emphysema and asthma. Lung cancers are characterized by thickening and callusing of cells lining the bronchi, loss of cilia, formation of a tumor that eventually metastasizes.