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6.4 Gas Exchange

Learn about the importance of breathing and the processes of ventilation, gas exchange, and cell respiration. Understand the components of the human respiratory system and how air is drawn into and pushed out of the lungs. Explore the adaptations of alveoli for efficient gas exchange.

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6.4 Gas Exchange

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  1. 6.4 Gas Exchange Respiratory System

  2. Why do we need to breathe? • To intake oxygen • To exhale carbon dioxide What is oxygen used for? • Aerobic respiration And what is aerobic respiration used for? • Energy production (ATP!)

  3. Definitions: Ventilation, Gas Exchange, and Cell Respiration • Ventilation • The process of inhaling and exhaling, with oxygen entering the alveoli (large surface area) • Gas Exchange • The process of exchanging one gas for the other between alveoli and capillaries (carbon dioxide for oxygen) • Cell Respiration • The chemical process occurring in mitochondria where energy is released as ATP

  4. What composes the human respiratory system? • Mouth • Nose • Trachea • Bronchi • Bronchioles • Lungs • Alveoli

  5. Identify the respiratory components. 6 1 7 3 2 3 4 5

  6. Be able to draw something like this.

  7. Why are alveoli shaped like they are? • Small alveoli increase surface area of tissue exposed to open air • Gases only have to go throughone layer of cells (thin capillary wall) to get into blood vessel • There are so many capillariesblood easily diffuses

  8. How is air drawn into the lungs? • Diaphragm muscle contracts • Intercostal muscles between ribs contract • Lungs can open up more • More volume with same amount of gas = decreasedair pressure • Air rushes into lungs to balance pressure

  9. How is air pushed out of the lungs? • Diaphragm muscle relaxes • Pushes on lungs to “deflate” • Intercostal muscles relax • Chest cavity gets smaller • Pushes air out of lungs • Air is exhaled

  10. IB Exam Question 1. State the difference between ventilation, gas exchange, and cell respiration. (3 marks) • Ventilation • The process of inhaling and exhaling, with oxygen entering the alveoli (large surface area) • Gas Exchange • The process of exchanging one gas for the other between alveoli and capillaries (carbon dioxide for oxygen) • Cell Respiration • The chemical process occurring in mitochondria where energy is released as ATP

  11. IB Exam Question 2. Draw a diagram of the human gas exchange system. (5 marks) Award [1] for each of the following structures clearly drawn and labelled. • mouth / nose; • trachea; • bronchi; • bronchioles; • lungs; • alveoli; • diaphragm; • ribs / rib eye / intercostal muscles;

  12. IB Exam Question 3. List the features of the alveoli that adapt them to gas exchange. (3 marks) • Alveoli increase surface area between blood and respiratory gases • Single layer of cells allows for short diffusion distance of gas into blood • Dense network of capillaries near the surface increases absorption

  13. IB Exam Question 4. Explain the need for, and the mechanism of, ventilation of the lungs in humans.(8 marks) • draws fresh air / oxygen into the lungs; • removal / excretion of CO2; • maintains concentration gradient of O2 / CO2 / respiratory gases; • diaphragm contracts; • intercostal muscles contract; • increased volume (of thorax / thoracic cavity); • decreasing air pressure in lungs; • air rushes in down air pressure gradient; • opposite of the above causes exhalation; • abdominal muscles contract during active exhalation; • elastic recoil of lungs helps exhalation;

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