0:00 In this video, we will look at what substances and cells are found in the blood 0:13 and what 0:14 they do. 0:15 So if we were to take a sample of our blood, put it inside the tube and spin it 0:19 around 0:20 in a centrifuge, the blood sample will separate into layers based on how dense 0:26 it is. 0:26 So here I drew three main layers that are found in the blood. 0:33 The least dense layer on the very top is the plasma, which makes up 55% of the 0:38 total blood 0:39 volume. 0:40 And this is essentially the water that makes up the blood. 0:43 Then the second layer is the Buffy coat layer, which makes up less than 1%. 0:51 And then we have the very dense layer, which is the very bottom, which is 0:55 essentially our 0:56 erythrocytes, the red blood cells that make up 45% of the total blood volume. 1:01 Within the plasma, the plasma is not only water, it also contains other 1:05 substances such as 1:06 clotting factors. 1:07 And we have 13 clotting factors which help us in forming clot and maintaining 1:16 hemostasis. 1:18 Now in this video we will mainly focus on the buffing coat layer. 1:22 And we won't focus that much on the plasma and red blood cell layer. 1:25 But I do have a specific video on the red blood cells and what they do. 1:31 So you can watch that and I'll provide the link. 1:34 So anyways, let's focus on the buffing coat layer, the middle layer that makes 1:39 up 1% of 1:39 the total blood volume. 1:42 The buffing coat layer contains two main things, platelets and leukocytes or 1:47 white blood cells, 1:49 leuko as in white. 1:52 Now platelets are essentially these small things that help in the clot 1:58 formation, in 1:59 forming clots. 2:01 So where do these platelets come from? 2:04 So how are they made? 2:05 Well, platelets originally come from cells. 2:11 So what happens is that you have this cell in the bone marrow that have gran 2:16 ules and 2:16 it will become or differentiate into these cell known as a megacarriode cell. 2:24 And these cell contains the actual granules still. 2:28 When the megacarriode, when the cell ruptures through some process, it will 2:32 actually release 2:33 part of its cells with the granules containing the granules. 2:38 And so these parts and these bits are what we know as platelets. 2:44 So platelets come from these megacarriode cells when they basically rupture. 2:52 And what platelets do is that, as I've mentioned, they help form clots together 2:56 with the help 2:57 of clotting factors that are found in the plasma. 3:02 But the other component of the buffing coat layer are leukocytes or white blood 3:08 cells. 3:08 Now there are so many types of white blood cells. 3:11 And what they do is that they help our body fight infections and all this other 3:17 stuff. 3:17 So they're essentially the immune response. 3:23 White blood cells can be divided broadly into two main parts. 3:28 White blood cells that do not contain granules called agranulocytes or granul 3:35 ocytes, white 3:36 blood cells that contain pathogen-combatting granules. 3:41 So they do contain granules. 3:43 Now we'll firstly focus on the granulocytes, the white blood cells that do 3:48 contain granules. 3:50 We have three main granulocytes in our system. 3:53 These are the neutrophils, iscinephils and basophils. 3:57 Let's look at each one of them and see what they do in a brief picture. 4:02 The neutrophils main function is phagocytosis of foreign agents such as 4:08 pathogens or debris. 4:10 In the process, they will blow up. 4:14 And so they're quite dangerous and highly inflammatory. 4:20 The iscinephils are basically cells that are part of the allergic response. 4:24 They secrete chemicals that will activate another cell called mast cells and 4:29 this will 4:29 essentially promote the allergic response. 4:34 Iscinephils also have a role in host defense against parasites, bacteria and 4:38 fungi. 4:39 And iscinephils are seen quite, they're a big factor in the pathogenesis of 4:48 asthma. 4:49 Then you have the basophils. 4:51 Now the basophils also secrete chemicals which promote the allergic response. 4:57 In mice, it's been found that basophils are also antigen-presenting cells which 5:03 are cells 5:04 that can activate T cells. 5:07 Okay, so those are the three granular sites. 5:11 Now let's look at the A granular sites, the cells that do not contain granules. 5:15 We have mast cells, dendritic cells, monocytes, T lymphocytes and B lymphocytes 5:22 . 5:23 Dendritic cells are extremely important cells in the innate immune response, 5:27 the first line 5:28 of defense. 5:29 They are phagocytes and are the main antigen-presenting cells and antigen- 5:34 presenting cells means 5:36 that these cells are cells that activate T cells, the T lymphocytes. 5:45 They look like they contain granules and they do but they are not classified as 5:51 granular 5:52 sites. 5:54 Mast cells release histamine and they are very big in the allergic response as 6:02 well 6:03 as inflammatory response. 6:05 And they release histamine when, if there's an allergy or in the presence of a 6:13 pathogen. 6:14 The release of histamine will cause vasodilation and increase in vascular perme 6:22 ability. 6:23 Now we have monocytes. 6:25 Monocytes circulate actually in the blood and they are phagocytes so they eat 6:31 up things. 6:32 But when a monocytes migrates from the blood into a tissue, the monocyte 6:36 becomes what's 6:37 known as a macrophage, big eaters. 6:41 Painters have many functions, phagocytes and they are also antigen-presenting 6:46 cells so 6:47 they activate T lymphocytes just like the dendritic cells. 6:52 So what are the T lymphocytes? 6:55 Where T lymphocytes or known as the T cells can be divided into two main types 7:02 of T cells. 7:03 These are the CD4 T cell and the CD8 T cell. 7:08 CD4 T cells are known as T helper cells and they essentially promote the mac 7:15 rophage activity 7:17 as well as they will activate the B cells or the B lymphocytes. 7:24 Now the CD8 T cells are known as the cytotoxic T cells and their main function 7:30 is to kill 7:30 infected cells, tumor cells or abnormal cells. 7:36 Now just to confuse you even further, both B and T lymphocytes can also form 7:42 memory cells 7:44 for a specific pathogen or antigen and so there's actually T memory cells. 7:54 So you have T helper cells, cytotoxic T cells and T memory cells. 8:00 Then you have the B lymphocytes. 8:02 The B lymphocytes or known as the B cells, they can be divided into plasma 8:09 cells or they 8:09 can be memory B cells once they are activated. 8:17 Plasma cells are socially secret antibodies that help combat allergens or 8:24 pathogens. 8:25 Then you have the memory B cells that are cells that form a specific memory to 8:30 a particular 8:31 antigen or agent. 8:34 I hope that was not too confusing that last bit. 8:37 If that was, you can watch a video on the immune system overview just to 8:43 understand what 8:44 these T and B cells actually do and how they are how they how they function. 8:53 So that concludes the video, I was going to talk a little bit about clotting 8:57 factors 8:58 but I realized I did a big mistake but anyway we have 13 clotting factors in 9:07 our body and 9:08 that concludes the video. 9:09 I hope you enjoyed it and thanks for watching.
