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Topic 6.4 Gas Exchange

Topic 6.4 Gas Exchange. 6.4.1 distinguish between:. Ventilation – breathing (air in and out of lungs) Gas Exchange – diffusion of gases. Occurs in 2 places: Cellular Respiration – What is it and where does it take place?. Diffusion.

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Topic 6.4 Gas Exchange

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  1. Topic 6.4 Gas Exchange

  2. 6.4.1 distinguish between: • Ventilation – breathing (air in and out of lungs) • Gas Exchange – diffusion of gases. Occurs in 2 places: • Cellular Respiration – What is it and where does it take place?

  3. Diffusion • Protists, sponges, cnidarians, and flatworms all obtain oxygen and get rid of carbon dioxide via diffusion with the aqueous environment in which they live. • In all animals, the respiratory surface must be moist and thin. In many it is highly branched to provide greater surface area.

  4. 6.4.2 Need for ventilation system • We are large so our surface area/volume ratio is not favorable for the diffusion of gases. • Our exterior surface (skin) is not suited for the exchange of gases. Respiratory surfaces should be moist. • A ventilation system ensures that the transfer of gases is encouraged due to concentration gradients.

  5. 6.4.4 AnatomyDraw and label • Nasal cavity – separated from mouth by palate. Warms, filters, moistens air • Pharynx – common passageway for respiration and digestion • Larynx – top of trachea, contains vocal cords. Opening to larynx is glottis, protected by epiglottis • Trachea – C shaped rings of cartilage support. Forks into 2 bronchi.

  6. Bronchi branch to form bronchioles • Tips of bronchioles end in clusters of air sacs called alveoli where gas exchange occurs.

  7. Each lung has about 300 million alveoli • Each alveoli cluster is surrounded by a capillary bed.

  8. 3.4.3 Alveolar structure • The small spherical shape of alveoli provide a large surface area for gas exchange • Single cell thickness makes it easy for gases to diffuse through alveoli wall • Moisture allows for efficient diffusion • Capillary bed ensures gases do not have to diffuse far to reach circulatory system

  9. Question • Pneumonia (excess mucus) and smoking (tar) create an extra lining inside of each of the alveoli. Describe how and why this could become life-threatening.

  10. Ventilation • Mammals – negative pressure breathing. • Recall that there is an inverse relationship between pressure and volume. • Diaphragm and intercostal muscles change the size of thoracic cavity which changes air pressure in lung. Air always flows from high pressure to low.

  11. Inspiration • Diaphragm contracts (moves down) and intercostal muscles raise rib cage. • Volume of thoracic cavity increases which lowers air pressure in lungs (partial vacuum) • Air flows from high pressure (atmosphere) to low pressure (lung) via your mouth/nasal passages trachea bronchi……

  12. Expiration • Diaphragm and intercostal muscles relax. Diaphragm rises and rib cage collapses. • Pressure in thoracic cavity increases. Air flows from high pressure (lung) to low pressure (atmosphere) and exits the way it entered.

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