2. External respiration Process of obtaining OXYGEN from the environment and eliminating CARBON DIOXIDE Internal respiration Exchange of OXYGEN CARBON DIOXIDE and between capillary blood and tissue fluids
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5. Diffusion The respiratory and circulatory systems are an integrated system. is influenced by a number of properties of the gas exchange surface. surface area x diffusion gradient thickness x material properties surface area – enhanced through gill lamellae, alveoli, sacculations diffusion gradient – increased by external (ventilation) and internal (heart) pumps thickness – reduced with membranes with a simple epithelium adjacent to endothelial lining of a capillary materials – must be easily diffusible
6. AGNATHANS Hagfishes in the genus Myxine have 5 or 6 pairs of gill pouches associated with the pharynx, while some species of Eptatretus have 5 to 15 pairs . afferent branchial ducts conduct respiratory water from the pharynx to the pouches. efferent branchial ducts lead from the pouches to the exterior.
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8. LAMPREYS The buccal cavity of lampreys is pressed tightly into the flesh of a host and the nasohypophyseal duct from the unpaired naris ends in a nasohypophyseal sac (not into the pharynx). = The nasal and buccal route are NOT AVAILABLE for the passage of respiratory water.
9. Respiratory water enters and exits the pharyngeal pouches via external gill slits . PHARYNX LAMPREYS subdivided longitudinally into an esophagus that continues to the stomach and a ventral respiratory tube that ends blindly 7 pairs of gill pouches > lined with gill lamellae > communicate directly with respiratory tube and exterior > with no intervening afferent or efferent branchial ducts
