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Download day 3 gas exchange
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Gas Exchange Gills Alveoli Why do we need a respiratory system? Need O2 (IN) for cellular respiration to make ATP food CO2 O2 Need CO2 (OUT) waste product from cellular respiration ATP What’s needed for gas exchange? need high surface area maximize gas exchange gases move across by diffusion need moist membrane maintains cell membrane structure gases only diffuse in water Gas exchange has many forms one-celled insects amphibians fish echinoderms mammals Gills: Countercurrent Water carrying gas flows in one direction, blood flows in opposite direction maintains diffusion gradient over whole length of gill capillary maximizing O2 transfer from water to blood Tracheal System air tubes branching throughout body gas exchanged by diffusion across moist cells lining terminal ends, not through open circulatory system Gas Exchange in Humans Concentration gradient & pressure drives movement of gases into & out of blood at both lungs & body tissue both oxygen and carbon dioxide diffuse from an area of high concentration to an area of lower concentration (see fig 11.9 page 452) capillaries in lungs capillaries in muscle O2 O2 O2 O2 CO2 CO2 CO2 CO2 blood lungs blood body How Blood Transports Gases - Both O2 and CO2 are transport by blood. - About 99% of O2 is carried by hemoglobin (protein in red blood cells) - About 23% of CO2 is carried by hemoglobin 77% is carried by blood fluid - When CO2 reaches the lungs, it diffuses into the air in the alveoli see figure 11.10 (page 453)
