Respiration Chapter 53 Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Fick’s Law of Diffusion Gas exchange is accomplished by diffusion Rate of diffusion between two regions is governed by Fick’s Law. R = D x A ( p/d) R = Rate of diffusion D = Diffusion Constant A = Area over which diffusion takes place. p = Differences in concentrations d = Distance across which diffusion takes place. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

How Animals Maximize the Rate of Diffusion Beating cilia producing water current. Respiratory organs that increase surface area available for diffusion. Bring external environment close to internal fluid. Atmospheric Pressure and Partial Pressures One atmosphere is 760 mm Hg. Partial Pressure is fraction contributed by a gas. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Gill as a Respiratory Structure External gills provide a greatly increased surface area for gas exchange. Disadvantages are that they must be moved constantly and are easily damaged. Gills of Bony Fish Located between buccal cavity and opercular cavity. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Gill as a Respiratory Structure Buccal cavity can be opened and closed by opening and closing the mouth. Opercular cavity can be opened and closed by movements of the operculum. Ram ventilation Blood flows in an opposite direction to the flow of water, thus maximizing oxygenation of blood. Countercurrent Flow. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Respiration in Air-Breathing Animals Gills replaced in terrestrial animals because: Air is less buoyant than water. Water vapor diffuses into the air through evaporation. Two Main terrestrial respiratory organs: Tracheae Lung Lungs use a uniform pool of air in constant contact with gas exchange surface. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Respiration in Amphibians and Reptiles Lungs of amphibians are formed as saclike outpouching of the gut. Amphibians force air into their lungs creating positive pressure. Fill buccal cavity with air, and then close mouth and nostrils and elevate floor of oral cavity. Reptiles expand their rib cages by muscular contraction and take air into lungs via negative pressure breathing. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Respiration in Mammals Lungs of mammals packed with Alveoli. Air brought to alveoli through system of air passages. Inhaled air taken to the larynx, passes through glottis into the trachea. Bifurcates into right and left bronchi which enter each lung and further subdivide into bronchioles that deliver air into alveoli. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

When air sacs are expanded during inspiration, they take in air. Respiration in Birds Bird lung channels air through tiny air vessels called parabronchi, where gas exchange occurs. Uni-directional flow. When air sacs are expanded during inspiration, they take in air. When they are compressed during expiration, they push air into and through the lungs. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Respiration in Birds Avian respiration occurs in two cycles. Each cycle has an inspiration and an expiration phase. Cross-current flow has the capacity to extract more oxygen from the air than a mammalian lung. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Structures and Mechanisms of Breathing The outside of each lung is covered by a visceral pleural membrane. Second parietal pleural membrane lines inner wall of thoracic cavity. Pleural cavity between the two membranes. Mechanics of Breathing Boyle’s Law - When the volume of a given quantity of gas increases, its pressure decreases. When the pressure within the lungs is lower than the atmospheric pressure, air enters the lungs. Thoracic volume increased by contraction of external intercostals and the diaphragm. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Structures and Mechanisms of Breathing Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Structures and Mechanisms of Breathing Breathing Measurements Tidal Volume - Volume of air moving into and out of the lungs. Vital Capacity - Maximum amount of air that can be expired after a forceful inspiration. Hypoventilating - Slow breathing - Too much carbon dioxide. Hyperventilating - Rapid Breathing - Not enough carbon dioxide. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Mechanisms That Regulate Breathing Rise in carbon dioxide causes blood pH to lower, stimulating neurons in the aortic and carotid bodies to send impulses to the control center in the medulla oblongata. Sends impulses to diaphragm and external intercostal muscles, stimulating them to contract, expanding chest cavity. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Hemoglobin and Oxygen Transport Hemoglobin is a protein composed of four polypeptide chains and four organic heme groups. Iron atom at center of each heme group. Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin. As blood passes through the capillaries, some of the oxyhemoglobin releases oxygen and become deoxyhemoglobin. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Hemoglobin and Oxygen Transport Oxygen transport in the blood is affected by many conditions. pH - Bohr’s Effect. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Carbon Dioxide and Nitric Oxide Transport About 8% of CO2 in blood is dissolved in plasma and another 20% is bound to hemoglobin. Remaining 72% of CO2 diffuses into red blood cells where carbonic anhydrase catalyzes the combination of CO2 with water to form carbonic acid. Blood flow and blood pressure are also regulated by the amount of NO released into the bloodstream. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies