Gaseous Exchange Questions for Your Exam

2672 WordsJan 20, 201311 Pages
us |3.4 Breathing System and |Objectives | |Excretion |At the end of this sub section students should be able to: | |3.4.4 Lungs & Breathing |Draw and identify the breathing tract in humans | | |Give the function of the parts: Nasal and buccal cavities, pharynx, epiglottis, glottis, larynx, trachea, bronchi, bronchioles, alveoli | | |Explain the essential features of the alveoli…show more content…
Finally it is removed from the lungs during expiration. CO2 is produced by respiration. Some dissolves in blood plasma, but most of it diffuses into the red blood cells. In the red cells an enzyme causes CO2 to combine rapidly with water to form carbonic acid. This then splits in two forming hydrogen ions and hydrogen carbonate ions. The hydrogen carbonate ions diffuse out into the plasma. Adaptations of alveoli for gas exchange: 1. Large surface area of contact between alveoli and blood capillaries - faster rate of gas exchange. 2. Alveoli and capillaries are only one-celled thick. The short distance between air and blood establishes a steep conc. gradient for rapid diffusion. 3. Slow blood flow gives max. time for oxygenation and excretion of carbon dioxide. 4. Alveoli are elastic for efficient inspiration and expiration. 5. Alveoli lining is moist - dissolved gases diffuse faster. Capillaries: 1. Capillaries are tightly packed (covering almost 90% of alveolar surface) - faster rate of exchange. 2. The capillaries are narrower in diameter than red blood corpuscles. Hence (1) a greater area of each R.B.C. is pressed against the capillary wall through which oxygen is diffusing and (2) R.B.C. are slowed down as they squeeze through the capillary thus increasing the time available for oxygen absorption. They have a tiny internal diameter Protection of

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