As you can imagine, cigarette smoke contains many impurities that are inhaled in great numbers directly into the lung. For this reason, the alveolar spaces of the smoker contain numerous scavenger cells (macrophages) that are filled with engulfed (phagocytized) particles of impurities and debris, as illustrated in Picture of scavenger cells in a smoker's alveolus Under the microscope, with this high magnification, you can actually see the black and brown engulfed particles in the alveolar scavenger cells. Indeed, smoker's lung may have so much of this particulate material that the lung looks gray-black to the naked eye. Most of the time, you don't need a microscope to tell if someone is or was a heavy smoker. A naked eye examination of a smoker's lung will usually reveal an enlarged gray-black lung with enlarged air spaces (the emphysema, as you saw in Figure 4 and will see again in Figure 8).
Students whose parents are not in the Foreign Service are eligible to participate if they are in grades nine through twelve in any of the fifty states, the District of Columbia, the . territories, or if they are . citizens attending high school overseas. Students may be attending a public, private, or parochial school. Entries from home-schooled students are also accepted. Previous first-place winners and immediate relatives of directors or staff of the AFSA and Semester at Sea are not eligible to participate. Previous honorable mention recipients are eligible to enter. $2,500 to the writer of the winning essay, in addition to an all-expense paid trip to the nation’s capital from anywhere in the . for the winner and his or her parents, and an all-expense paid educational voyage courtesy of Semester at Sea.