Anatomy & Physiology

Anatomy & Physiology Study Guide The vital capacity is the maximum amount of air that you can move into or out of your lungs in a single respiratory cycle. The maximum amount of air a person can move in and out of their lungs during a single respiratory cycle is known as the vital capacity. To calculate the vital capacity add together the tidal volume, inspiratory reserve volume, and the expiratory reserve volume. The result is typically 4800 mL in males and 3400 mL in females. • The total volume of your lungs is equal to your lung capacity , calculated by adding the vital capacity and the residual volume. The total lung capacity averages around 6000 mL in males and 4200 mL in females. 22.6 The Gas Laws The principles, known as gas laws that govern the movement and diffusion of gas molecules, such as those in the atmosphere are relatively straightforward. Through diffusion, gases are exchanged between the alveolar air and the blood which occurs in response to concentration gradients. Boyle’s Law Boyle’s Law states: The pressure of a gas decreases if the volume of the container increases, and vice versa. Air flows into the lungs from a region of higher pressure (the atmosphere) into an area of lower pressure (the intrapulmonary region). When the volume of the thoracic cavity increases even slightly during inhalation, the intrapulmonary pressure decreases slightly, and air flows into the lungs through the conducting airways. Dalton's Law and Partial P essures The air we breathe is not a single gas but a mixture of gases. Nitrogen molecules (N 2 ) are the most abundant, accounting for about 78.6 percent of atmospheric gas molecules. Oxygen molecules (O 2 ), the second most abundant, make up roughly 20.9 percent of air. The remaining 0.5 percent consists mostly of water molecules, with carbon dioxide (CO 2 ) contributing a mere 0.04 percent. Atmospheric pressure, 760 mm Hg, represents the combined effects of collisions involving each type of molecule in the air. At any moment, 78.6 percent of those collisions will involve nitrogen molecules, 20.9 percent oxygen molecules, and so on. Thus, each of the gases contributes to the total pressure in proportion to its relative abundance. This relationship is known as Dalton's law. The partial pressure of a gas (abbreviated P or p) is the pressure contributed by a single gas in a mixture of gases. All the partial pressures added together equal the total pressure exerted by the gas mixture. Diffusion Betw en Liquids and Gases (Henry's Law) The movement of gas molecules from one location to another (including in and out of solutions) is caused by the differences in pressure. At a given temperature, the amount of a particular gas in solution is directly proportional to the partial pressure of that gas. This principle is known as Henry's law. When gas under pressure contacts a liquid, the pressure tends to force gas molecules into solution. At a given pressure, the number of dissolved gas molecules will rise until an equilibrium is established. At equilibrium, the total number of gas molecules in solution remains constant due to Achieve Page 306 of 368 • ©2018