1 00:00:00,275 --> 00:00:03,030 - [Voiceover] This chapter's looking at how cells 2 00:00:03,030 --> 00:00:05,877 end up making themselves into organs. 3 00:00:05,877 --> 00:00:09,160 These cells that are grouped together have to have 4 00:00:09,160 --> 00:00:10,769 a common function. 5 00:00:10,769 --> 00:00:14,549 So a tissue is groupings of cells with a common function, 6 00:00:14,549 --> 00:00:15,948 they work together. 7 00:00:15,948 --> 00:00:19,590 You cannot just grab a cell from the brain, 8 00:00:19,590 --> 00:00:22,118 a cell from the kidney, one from the leg, 9 00:00:22,118 --> 00:00:25,582 and one from your spleen, doesn't work that way. 10 00:00:25,582 --> 00:00:30,361 The cells must work together to form a common function. 11 00:00:30,361 --> 00:00:34,278 Now we have four primary categories of tissues. 12 00:00:35,144 --> 00:00:39,311 We have the epithelial tissues, connective tissues, 13 00:00:40,203 --> 00:00:43,036 muscle tissue, and nervous tissue. 14 00:00:43,972 --> 00:00:46,763 The nervous tissue is probably the easiest one, 15 00:00:46,763 --> 00:00:49,885 because there's only one type of nervous tissue. 16 00:00:49,885 --> 00:00:53,585 The nervous tissues are what contains neurons. 17 00:00:53,585 --> 00:00:57,467 Makes up your brain, your spinal cord, your nerves. 18 00:00:57,467 --> 00:01:01,237 Now the muscle tissue, there's actually three types. 19 00:01:01,237 --> 00:01:05,237 One type is your cardiac muscle, cardiac, heart. 20 00:01:07,068 --> 00:01:09,255 It's the muscles that make up your heart. 21 00:01:09,255 --> 00:01:11,663 We have smooth muscle. 22 00:01:11,663 --> 00:01:15,037 Smooth muscle is found around organs. 23 00:01:15,037 --> 00:01:19,581 Think your stomach, your intestines, things like that. 24 00:01:19,581 --> 00:01:22,527 And then there's skeletal muscle. 25 00:01:22,527 --> 00:01:25,330 Skeletal muscle is what you typically think of 26 00:01:25,330 --> 00:01:27,225 when you think of muscle. 27 00:01:27,225 --> 00:01:30,484 These are the muscles attached to your bones. 28 00:01:30,484 --> 00:01:34,014 Things like biceps brachii, triceps brachii, 29 00:01:34,014 --> 00:01:37,495 pectoralis major, it's all the main muscles we think of 30 00:01:37,495 --> 00:01:40,412 when you voluntarily move a muscle. 31 00:01:42,162 --> 00:01:45,502 The other two categories, connective and epithelia, 32 00:01:45,502 --> 00:01:49,425 they have quite a few different tissues in each. 33 00:01:49,425 --> 00:01:53,443 So the connective tissues, you can kinda guess what they do, 34 00:01:53,443 --> 00:01:56,099 they're meant to connect one part to another, no problem. 35 00:01:56,099 --> 00:01:58,655 Epithelial, well they're meant to either cover 36 00:01:58,655 --> 00:02:00,488 or line the inside of. 37 00:02:04,273 --> 00:02:07,259 So here's a little schematic showing nervous tissue. 38 00:02:07,259 --> 00:02:09,706 You've got brain, spinal cord, nerves, sure, no problem. 39 00:02:09,706 --> 00:02:12,840 I already mentioned the three types of muscle tissue. 40 00:02:12,840 --> 00:02:17,045 But let's jump down to the epithelial tissue. 41 00:02:17,045 --> 00:02:19,157 The way the book's putting it is boundaries 42 00:02:19,157 --> 00:02:22,007 between different environments. 43 00:02:22,007 --> 00:02:24,813 Well the function is protection, secretion, 44 00:02:24,813 --> 00:02:27,146 absorption, even filtration. 45 00:02:28,754 --> 00:02:32,921 Your skin is going to be a partly epithelial tissue. 46 00:02:35,121 --> 00:02:38,029 Now it says epidermis in parentheses, 47 00:02:38,029 --> 00:02:41,516 that's because your skin actually has multiple layers. 48 00:02:41,516 --> 00:02:44,475 Only the more superficial, the ones you can touch, 49 00:02:44,475 --> 00:02:48,357 towards the surface, are going to be the epidermis. 50 00:02:48,357 --> 00:02:50,118 That's epithelial. 51 00:02:50,118 --> 00:02:54,420 The deeper part of your skin is actually connective tissue. 52 00:02:54,420 --> 00:02:56,982 Connective tissue itself supports, protects, 53 00:02:56,982 --> 00:02:59,374 binds, helps hold things together 54 00:02:59,374 --> 00:03:02,622 or transports from point A to point B. 55 00:03:02,622 --> 00:03:04,960 Bones are a great example. 56 00:03:04,960 --> 00:03:06,960 Your bones give support. 57 00:03:08,102 --> 00:03:11,117 They also give protection of certain organs. 58 00:03:11,117 --> 00:03:14,295 You have your tendons connecting muscle and bone, 59 00:03:14,295 --> 00:03:17,496 fat is gonna be a connective tissue. 60 00:03:17,496 --> 00:03:20,670 Even blood is a connective tissue. 61 00:03:20,670 --> 00:03:24,327 So it's helping it get from point A to point B. 62 00:03:24,327 --> 00:03:27,327 The four different types of tissues. 63 00:03:29,575 --> 00:03:31,486 Let's look a little more specifically 64 00:03:31,486 --> 00:03:33,694 at each type of tissue. 65 00:03:33,694 --> 00:03:35,935 The epithelial tissue, I already said, 66 00:03:35,935 --> 00:03:39,213 lines the body cavities or covers your surface. 67 00:03:39,213 --> 00:03:41,087 So it's the outside of your skin, 68 00:03:41,087 --> 00:03:42,625 it's the inside of your stomach, 69 00:03:42,625 --> 00:03:45,700 the inside of your oral cavity, your mouth. 70 00:03:45,700 --> 00:03:48,700 But you also have epithelial tissues 71 00:03:49,541 --> 00:03:51,958 that are glandular epithelia. 72 00:03:52,932 --> 00:03:57,099 This glandular epithelia is going to be some structure 73 00:03:59,029 --> 00:04:01,557 that can secrete or produce. 74 00:04:01,557 --> 00:04:04,557 These epithelial cells have adapted. 75 00:04:05,922 --> 00:04:07,707 Instead of covering or lining, 76 00:04:07,707 --> 00:04:10,874 they actually make up an entire gland. 77 00:04:13,428 --> 00:04:16,627 We have exocrine glands, for example. 78 00:04:16,627 --> 00:04:20,000 They're secreting right on to the exterior of the body. 79 00:04:20,000 --> 00:04:21,942 So you start looking at this diagram, 80 00:04:21,942 --> 00:04:23,888 you'll see that's an example of your skin. 81 00:04:23,888 --> 00:04:27,724 The glands are secreting right on the skin's surface. 82 00:04:27,724 --> 00:04:30,557 But we also have endocrine glands. 83 00:04:32,330 --> 00:04:35,497 Well, endo is inside, E-N-D-O, inside. 84 00:04:36,785 --> 00:04:41,628 And endocrine glands, they do not secrete onto the exterior 85 00:04:41,628 --> 00:04:45,795 body or the surface, they secrete right into the blood. 86 00:04:47,765 --> 00:04:51,868 Your endocrine glands secrete directly into the blood. 87 00:04:51,868 --> 00:04:55,839 They're secreting their hormones directly into the blood. 88 00:04:55,839 --> 00:05:00,726 So this epithelial tissue can either cover or line a cavity, 89 00:05:00,726 --> 00:05:03,976 but it also can be glandular epithelia. 90 00:05:07,560 --> 00:05:10,883 We start looking at the different types of epithelia. 91 00:05:10,883 --> 00:05:14,883 They're based on number of layers and the shape. 92 00:05:16,954 --> 00:05:20,037 With three primary shapes to look at. 93 00:05:21,147 --> 00:05:23,647 One is referred to a squamous. 94 00:05:24,859 --> 00:05:28,192 Squamous is a flattened, very thin cell. 95 00:05:29,806 --> 00:05:31,703 If you look at that little drawing to the right, 96 00:05:31,703 --> 00:05:34,430 you'll see how one is giving you kind of a 97 00:05:34,430 --> 00:05:36,524 three dimensional perspective, 98 00:05:36,524 --> 00:05:38,596 showing you how flat it can be. 99 00:05:38,596 --> 00:05:41,030 And the other one that is the furthest to the right, 100 00:05:41,030 --> 00:05:43,736 shows how very thin it can be. 101 00:05:43,736 --> 00:05:47,556 That purple is meant to be the nucleus. 102 00:05:47,556 --> 00:05:49,227 You kind of think of the squamous cell 103 00:05:49,227 --> 00:05:51,301 like an easy over egg. 104 00:05:51,301 --> 00:05:54,418 The nucleus, or in the case of an egg, the yolk, 105 00:05:54,418 --> 00:05:57,167 is in the center, with everything else spreading out 106 00:05:57,167 --> 00:05:59,417 around a very flat surface. 107 00:06:01,297 --> 00:06:03,714 Cuboidal, well what's a cube? 108 00:06:04,720 --> 00:06:06,086 A box. 109 00:06:06,086 --> 00:06:09,503 Cuboidal cells are gonna look like a box. 110 00:06:10,615 --> 00:06:13,170 Now they're not the perfect 90 degree corners, 111 00:06:13,170 --> 00:06:15,403 but they're gonna be close. 112 00:06:15,403 --> 00:06:18,820 They're more box-like than they are flat. 113 00:06:19,868 --> 00:06:23,035 Columnar, well what shape is a column? 114 00:06:24,043 --> 00:06:25,876 It's a tall rectangle. 115 00:06:26,809 --> 00:06:30,426 Again, these corners are not a perfect 90 degrees, 116 00:06:30,426 --> 00:06:34,458 but they're more columnar than they are box-like. 117 00:06:34,458 --> 00:06:37,644 And then they are flat, like squamous. 118 00:06:37,644 --> 00:06:42,316 So squamous, cuboidal, columnar, are the three main shapes 119 00:06:42,316 --> 00:06:45,316 to classify your epithelial tissues. 120 00:06:47,570 --> 00:06:51,516 And so the other type of classification was layering. 121 00:06:51,516 --> 00:06:53,646 Well if you have a single layer, 122 00:06:53,646 --> 00:06:55,896 it's referred to as simple. 123 00:06:56,935 --> 00:06:59,219 Now these simple layers are very thin, 124 00:06:59,219 --> 00:07:01,723 it's really easy for different particles 125 00:07:01,723 --> 00:07:05,056 to fuse across them, simply flow across. 126 00:07:06,448 --> 00:07:10,142 For example, the inside lining of your lungs. 127 00:07:10,142 --> 00:07:12,771 You have to have exchange of gases, 128 00:07:12,771 --> 00:07:14,612 oxygen, carbon dioxide. 129 00:07:14,612 --> 00:07:18,195 Well, you have simple squamous tissue here. 130 00:07:19,377 --> 00:07:22,558 Simple one-layer squamous flat makes it 131 00:07:22,558 --> 00:07:25,740 really efficient to have different gases 132 00:07:25,740 --> 00:07:29,485 moving through the membranes of your lungs. 133 00:07:29,485 --> 00:07:33,970 But sometimes you don't want things to pass through. 134 00:07:33,970 --> 00:07:36,646 That's when you have multiple layers. 135 00:07:36,646 --> 00:07:40,813 So you have two ore more layers referred to as stratified. 136 00:07:42,769 --> 00:07:46,686 This stratified is meant to provide protection. 137 00:07:48,245 --> 00:07:51,739 Your skin is a great example of stratified. 138 00:07:51,739 --> 00:07:54,380 If you happen to brush up against something, 139 00:07:54,380 --> 00:07:56,694 more often than not, it does not cut you, 140 00:07:56,694 --> 00:07:59,242 it does not rip your skin off. 141 00:07:59,242 --> 00:08:01,130 Instead, how does skin work? 142 00:08:01,130 --> 00:08:04,845 Well, a few layers of dead cells get rubbed off, 143 00:08:04,845 --> 00:08:07,845 the rest of the skin remains intact. 144 00:08:08,865 --> 00:08:11,782 So we have one layer called simple, 145 00:08:12,918 --> 00:08:15,751 multiple layers called stratified. 146 00:08:19,045 --> 00:08:21,719 So here are some examples of what we're looking at. 147 00:08:21,719 --> 00:08:25,949 We can take the first term, which is how many layers, 148 00:08:25,949 --> 00:08:28,902 and the second term, the shape. 149 00:08:28,902 --> 00:08:31,569 Simple squamous is the top left. 150 00:08:33,793 --> 00:08:36,430 Look at the example of the lungs. 151 00:08:36,430 --> 00:08:38,763 Great for exchange of gases. 152 00:08:39,722 --> 00:08:43,889 Going down, below simple squamous, you have simple cuboidal. 153 00:08:45,045 --> 00:08:48,468 The simple cuboidal, you see the cells, again, 154 00:08:48,468 --> 00:08:51,885 are one layer, but they're more box-like. 155 00:08:53,242 --> 00:08:57,307 Go below that, you get the simple columnar. 156 00:08:57,307 --> 00:09:01,487 Again, one layer of cells, but if you notice, 157 00:09:01,487 --> 00:09:05,654 they're tall, more column-like than they are box-like. 158 00:09:06,817 --> 00:09:08,468 Now, that has a labeling, 159 00:09:08,468 --> 00:09:10,658 of what they call a goblet cell in there. 160 00:09:10,658 --> 00:09:13,138 You can see that more of a reddish-pink color 161 00:09:13,138 --> 00:09:14,898 is actually a goblet cell. 162 00:09:14,898 --> 00:09:19,065 A goblet cell is going to be a glandular epithelial cell. 163 00:09:21,985 --> 00:09:26,764 It's actually going to produce and secrete a mucous. 164 00:09:26,764 --> 00:09:31,152 So the goblet cell's kind of a specialized structure there. 165 00:09:31,152 --> 00:09:33,603 If we go to the right side, you can see, 166 00:09:33,603 --> 00:09:36,942 we start with the right top is stratified squamous. 167 00:09:36,942 --> 00:09:40,692 Stratified means many layers, squamous, flat. 168 00:09:42,535 --> 00:09:44,744 Now if you're looking at this and saying hold on, hold on, 169 00:09:44,744 --> 00:09:48,112 I see the top looks flat, but as you go to the bottom, 170 00:09:48,112 --> 00:09:49,791 those look cube-like. 171 00:09:49,791 --> 00:09:53,355 The trick here is with all stratified tissue, 172 00:09:53,355 --> 00:09:56,471 the name of the cell shape is based on 173 00:09:56,471 --> 00:09:59,304 the most superficial or top layer. 174 00:10:01,412 --> 00:10:04,343 The top layer here are flat cells, 175 00:10:04,343 --> 00:10:06,593 hence, stratified squamous. 176 00:10:07,595 --> 00:10:10,238 Next one down, stratified cuboidal, no problem, 177 00:10:10,238 --> 00:10:11,999 you can tell that one. 178 00:10:11,999 --> 00:10:16,095 Stratified columnar, again, look at the different shapes. 179 00:10:16,095 --> 00:10:18,727 The naming's based on many layers, 180 00:10:18,727 --> 00:10:21,385 but also what's the most superficial, 181 00:10:21,385 --> 00:10:24,353 what's the exposed surface? 182 00:10:24,353 --> 00:10:26,905 These are going to be columnar cells, 183 00:10:26,905 --> 00:10:29,155 hence, stratified columnar. 184 00:10:33,959 --> 00:10:35,899 But some of these cells need to have a little bit 185 00:10:35,899 --> 00:10:40,066 of extra support, ways of holding themselves together. 186 00:10:41,026 --> 00:10:42,529 So what we're seeing right here 187 00:10:42,529 --> 00:10:45,029 are two simple columnar cells. 188 00:10:46,549 --> 00:10:48,478 You can see it's one layer, and they're tall columns, 189 00:10:48,478 --> 00:10:52,485 but they look like they're almost stitched together, 190 00:10:52,485 --> 00:10:55,323 like someone took a sewing machine and just sewed 'em. 191 00:10:55,323 --> 00:10:59,255 What that is is called a tight junction. 192 00:10:59,255 --> 00:11:01,915 The whole purpose of a tight junction 193 00:11:01,915 --> 00:11:06,082 is to hold two epithelial cells very close and very tight. 194 00:11:08,444 --> 00:11:10,519 It prevents things from passing between the cells, 195 00:11:10,519 --> 00:11:14,190 because instead of a very thin space, 196 00:11:14,190 --> 00:11:17,190 there is no space between the cells. 197 00:11:18,285 --> 00:11:21,025 They're basically stitched together to prevent 198 00:11:21,025 --> 00:11:23,192 passage between the cells. 199 00:11:26,851 --> 00:11:30,018 We then have these adhesion junctions. 200 00:11:31,529 --> 00:11:33,167 Look at these adhesion junctions, 201 00:11:33,167 --> 00:11:35,555 doesn't look like they're mostly stitched together, 202 00:11:35,555 --> 00:11:38,962 but we have these little lines that interlock. 203 00:11:38,962 --> 00:11:43,525 With adhesion junctions, you can kinda think of it 204 00:11:43,525 --> 00:11:48,272 as a zipper, those little purple fibers that interlock? 205 00:11:48,272 --> 00:11:50,838 They're interlocking like a zipper would be. 206 00:11:50,838 --> 00:11:52,859 They're gonna hold together and make sure 207 00:11:52,859 --> 00:11:55,201 the cells do not separate. 208 00:11:55,201 --> 00:11:59,368 But you can see there still is some space between the cells. 209 00:12:00,787 --> 00:12:03,515 So their point here is now allowing some flexibility, 210 00:12:03,515 --> 00:12:07,182 but still anchoring the cells to each other. 211 00:12:08,607 --> 00:12:12,537 And the third one here, called gap junctions. 212 00:12:12,537 --> 00:12:14,442 If you look at the blown-up picture, 213 00:12:14,442 --> 00:12:17,663 you can see they're still holding the cells together, 214 00:12:17,663 --> 00:12:21,699 but there's an open channel in the middle. 215 00:12:21,699 --> 00:12:25,866 Gap junctions are meant to allow transfer of ions. 216 00:12:28,191 --> 00:12:29,691 Transfer of water. 217 00:12:30,734 --> 00:12:34,078 They allow different particles to go from one cell 218 00:12:34,078 --> 00:12:37,436 to the adjacent cell next to it. 219 00:12:37,436 --> 00:12:41,436 So the gap junctions are a little, tiny channel. 220 00:12:42,484 --> 00:12:46,941 So gap junctions, adhesion junctions, tight junctions, 221 00:12:46,941 --> 00:12:49,216 they all have their own purpose, 222 00:12:49,216 --> 00:12:53,311 but they all hold something to something else. 223 00:12:53,311 --> 00:12:55,093 They're anchoring cells together, 224 00:12:55,093 --> 00:12:58,738 but tight junction is no space at all. 225 00:12:58,738 --> 00:13:00,507 It's waterproof. 226 00:13:00,507 --> 00:13:03,117 Adhesion junction, you have some space, 227 00:13:03,117 --> 00:13:05,790 therefore, little bit flexibility. 228 00:13:05,790 --> 00:13:09,957 The gap junctions, allow for particles to pass cell to cell.