هل تعرف وظائف اعضاء جسمك؟ سلسلة تعريفية بدون تعقيدات اكاديمية

Quote: One of my major tasks is cleaning and conditioning the air for Joe's lungs. Each day I must process about 500 cubic feet of air--a small roomful. Joe may be skiing on a frigid, dry day, but his lungs are not interested in dry, zero air. They want about what one would find on a humid summer day--75 to 80 percent saturated, temperature in the 90s. They demand air almost totally free of bacteria, and cleansed of grit, smoke and other irritants. The air conditioner for a medium-sized mom is as large as a small trunk. My air-conditioning system is compressed into a tiny area only a few centimeters long. For the humidifying job I secrete about a liter of moisture a day. Mostly this is sticky mucus, produced by the spongy, red membrane that lines my passages. While the rough cleaning job is done by hairs in Joe's nostrils, it is the mucus that does the major work, acting as a kind of flypaper to trap bacteria and particles that get past the hairs. Naturally, I cannot permit this film of mucus to stagnate. In a few hours there would be total pollution. So every 20 minutes I produce a clean new mucous blanket. To remove the old mucus, I have an army of microscopic brooms--cilia. These minute hairs rapidly whip the film back to the throat for swallowing and then slowly settle back to their original positions. Strong stomach acid destroys most swallowed bacteria. My tireless little cilia make about ten sweeping stroke a second. Joe, of course, is unaware of this activity, which goes on day and night. But on a cold day he becomes aware of it, since cold partially paralyses my cilia and causes overproduction of mucus. Then, instead of being swept back to the throat, the moisture dribbles out the front.

(عدل بواسطة احمد سيد احمد on 09-21-2014, 11:43 AM)
(عدل بواسطة احمد سيد احمد on 09-21-2014, 06:57 PM)