1 00:00:00,000 --> 00:00:04,760 Hi, Dr. D. Hi, kids. 2 00:00:04,760 --> 00:00:07,080 We need to learn more about cells and how they operate. 3 00:00:07,080 --> 00:00:08,080 Can you help us? 4 00:00:08,080 --> 00:00:09,080 Sure. 5 00:00:09,080 --> 00:00:14,000 A cell is a basic building block of the body, and your body has about 10 trillion cells. 6 00:00:14,000 --> 00:00:15,000 10 trillion? 7 00:00:15,000 --> 00:00:18,080 That's a one followed by 13 zeros. 8 00:00:18,080 --> 00:00:19,080 That's a lot. 9 00:00:19,080 --> 00:00:21,840 Here are some examples of cells you might find in your body. 10 00:00:21,840 --> 00:00:25,880 This nerve cell is long and has a lot of branches. 11 00:00:25,880 --> 00:00:28,280 It's very different from this white blood cell. 12 00:00:28,280 --> 00:00:29,280 What do they both have in common? 13 00:00:29,560 --> 00:00:31,880 Well, it looks like they all have that thing in the middle. 14 00:00:31,880 --> 00:00:33,600 That thing in the middle is called the nucleus. 15 00:00:33,600 --> 00:00:37,040 They also have a membrane which holds the cells together. 16 00:00:37,040 --> 00:00:41,720 And this semi-fluid region inside of each cell is called the cytoplasm. 17 00:00:41,720 --> 00:00:42,720 That's cool. 18 00:00:42,720 --> 00:00:46,280 Over there you have what looks like a lot of cells together. 19 00:00:46,280 --> 00:00:47,280 What's that called? 20 00:00:47,280 --> 00:00:51,080 Cells of the same structure and function that are grouped together are called tissue, like 21 00:00:51,080 --> 00:00:55,160 this muscle tissue or like this tissue, which is the outer layer of the skin. 22 00:00:55,160 --> 00:00:57,720 This skin model looks like shingles on a roof. 23 00:00:57,720 --> 00:00:58,720 Very good. 24 00:00:59,160 --> 00:01:01,800 It's designed to keep moisture in and microbes out. 25 00:01:01,800 --> 00:01:04,840 Now when you combine various tissues together, you get an organ. 26 00:01:04,840 --> 00:01:07,000 You mean like a heart or the lung? 27 00:01:07,000 --> 00:01:08,000 Exactly. 28 00:01:08,000 --> 00:01:10,320 Now here's a model of the largest organ in the body. 29 00:01:10,320 --> 00:01:11,320 It looks like skin. 30 00:01:11,320 --> 00:01:12,320 It is. 31 00:01:12,320 --> 00:01:16,920 Now, when you combine two or more organs that have a common task, they're called an organ 32 00:01:16,920 --> 00:01:17,920 system. 33 00:01:17,920 --> 00:01:20,800 Dr. Texboat mentioned something about body systems. 34 00:01:20,800 --> 00:01:23,920 Let's look at this human torso as an example. 35 00:01:23,920 --> 00:01:25,320 This is the digestive system. 36 00:01:25,520 --> 00:01:32,160 It starts with the teeth, the tongue and salivary glands, then the esophagus, then the stomach 37 00:01:32,160 --> 00:01:33,480 and the intestines. 38 00:01:33,480 --> 00:01:35,840 They all work together to digest food. 39 00:01:35,840 --> 00:01:37,240 The body is very complex. 40 00:01:37,240 --> 00:01:38,400 Yes, it is. 41 00:01:38,400 --> 00:01:41,400 It's amazing how the systems work together for the good of the body. 42 00:01:41,400 --> 00:01:43,800 The body works really hard to keep itself in homeostasis. 43 00:01:43,800 --> 00:01:47,320 Wait a minute, Dr. D. That's a big word. 44 00:01:47,320 --> 00:01:48,320 Okay. 45 00:01:48,320 --> 00:01:52,800 Homeostasis means keeping the body's internal environment, like its temperature, fairly 46 00:01:52,800 --> 00:01:53,800 constant. 47 00:01:53,800 --> 00:01:57,840 The body has what are called feedback controls that act to reverse any changes. 48 00:01:57,840 --> 00:01:58,840 It's like a thermostat. 49 00:01:58,840 --> 00:02:01,640 Let me show you how a thermostat works. 50 00:02:01,640 --> 00:02:04,920 When I heat up this bimetal strip, it bends upward. 51 00:02:04,920 --> 00:02:10,160 When it touches this rod, it makes an electrical connection, which turns on this fan and cools 52 00:02:10,160 --> 00:02:11,160 things down. 53 00:02:11,160 --> 00:02:15,880 Then when the metal becomes cooler, it straightens out and breaks the electrical connection and 54 00:02:15,880 --> 00:02:18,600 turns off the fan. 55 00:02:18,600 --> 00:02:21,640 That's pretty cool, but what does it have to do with the body? 56 00:02:21,640 --> 00:02:25,680 When the body heats up, the feedback controls cause the body to perspire, and the blood 57 00:02:25,680 --> 00:02:28,600 vessels near the skin dilate or get larger in diameter. 58 00:02:28,600 --> 00:02:33,440 When the perspiration evaporates, it cools the body, and the increased blood flow to 59 00:02:33,440 --> 00:02:36,080 the larger vessels also releases more heat. 60 00:02:36,080 --> 00:02:40,960 So when these things cool the body down, the perspiration stops and the blood vessels return 61 00:02:40,960 --> 00:02:41,960 to normal? 62 00:02:41,960 --> 00:02:42,960 That's right. 63 00:02:42,960 --> 00:02:45,280 So are different body systems affected differently? 64 00:02:45,280 --> 00:02:46,280 Yes. 65 00:02:46,280 --> 00:02:50,280 Some systems, like the digestive and the respiratory systems, are more susceptible to infection. 66 00:02:50,280 --> 00:02:51,280 Do you know why? 67 00:02:51,420 --> 00:02:55,280 I guess we all have to eat and breathe, and viruses and bacteria can get into the food 68 00:02:55,280 --> 00:02:57,280 that we eat and the air that we breathe. 69 00:02:57,280 --> 00:02:58,280 That's right. 70 00:02:58,280 --> 00:03:01,960 Thanks, Dr. D, but we still need to learn more about how cells are infected. 71 00:03:01,960 --> 00:03:02,960 I thought you might. 72 00:03:02,960 --> 00:03:07,480 When you take your petri dishes to Mr. Frank at TCC this afternoon, you can also ask him 73 00:03:07,480 --> 00:03:08,480 about infection. 74 00:03:08,480 --> 00:03:09,480 Great. 75 00:03:09,480 --> 00:03:10,480 Thanks, Dr. D. 76 00:03:10,480 --> 00:03:11,480 You're welcome. 77 00:03:11,480 --> 00:03:12,200 Let me know what you find out.