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Course: Health and medicine > Unit 6
Lesson 1: Blood and blood cellsHematopoiesis
Hematopoiesis is the process of creating new blood cells in the body. All blood cells start off as hematopoietic stem cells, and then specialize (differentiate) into myeloid cells (erythrocytes, megakaryocytes, monocytes, neutrophils, basophils, or eosinophils) or lymphoid cells (T-lymphocytes and B-lymphocytes). Created by Nauroz Syed.
Want to join the conversation?
- NK cells are also lymphocytes. Do they originate from lymphoblasts as well?(7 votes)
- Yes they do, they are a third descendant.
She forgot to draw them in.(5 votes)
- What is the purpose of most of these cells? Could you have too much of them?(4 votes)
- Red blood cells bring oxygen to your cells, among other tasks.
Megakaryocytes make platelets, which are needed to help form clots and prevent bleeding.
Most other cells (white blood cells) produced by the bone marrow are involved in the immune system, helping to fight off infections, cancer, foreign particles, etc.
You can definitely have too much of any of these. Too many platelets, for example, could cause too much clotting, leading to risks of stroke or heart attack. If the bone marrow is filled up by too many of one kind of cell (as in various leukemias), there may not be enough space to make the other types.(4 votes)
- are there more cell groups than lyphoid and myeloid cell groups(5 votes)
- yes there are in fact there are things like toe cells!(2 votes)
- Are the basophil and eosinophil red and blues actually present naturally or do they just stain that way?(2 votes)
- They're named after the stains! Eosin is a red acidic stain that stains basic particles like proteins. Basophilic dyes are basic (like hematoxylin) and stain blue/purple and stain acidic particles like nucleic acids.(6 votes)
- Isnt a enthosite a red blood cell?(2 votes)
- Don't forget about discocyte... mainly because of the shape... :)(1 vote)
- what happens when hematopoiesis goes wrong or something like that?(2 votes)
- what is a red blood cell? from Riley Murillo(2 votes)
- The red blood cell is a very special cell in your body. It contains hemoglobin which gives blood its red colour and as well will let the RBC transport oxygen and carbon dioxide to and from various tissues within you body! Very important little guys!(3 votes)
- For what level of study is this video intended? For Medical school or premed, or high school biology?(4 votes)
- I am in college and I don't have to learn this. I am taking Biology.(1 vote)
- Are the basophil and eosinophil really that color or is that how they are stained to see them under the microscope?(2 votes)
- The cells are stained. Basophiles have granules that absorb the blue stain. Eosinophils' granules stain red and neutrophils' granules are gray or neutral staining. The original stain is Wright's Stain, with Methylene blue and Eosin but Diff quick also stains the cells
In a similar way so we can distinguish one from another under the microscope.(2 votes)
- is their more cells that you did not talk about?(2 votes)
- Yes. There are plenty of cells in our body, like brain cells, fat cells, and many others too!!(2 votes)
Video transcript
Voiceover: I'm gonna start
by drawing a blood vessel. Inside the blood vessel I'm gonna draw in some of the cells that you'd
expect to see in normal blood. I'm gonna put in a few red blood cells. I'm gonna draw in a couple of platelets which are just fragments of cells and then I'm gonna put in
a few white blood cells. Even though all of these
cells are found in the blood they're actually not made there. The cells in the blood
are made inside the bone. If you were to take a
cross section of bone, if you were to take a slice like this and you looked at it, you'd see that on the inside of bone there's a central cavity. This is the outside part of the bone. The hard part and this
is the central cavity. Inside that cavity there's
this red spongy tissue. That stuff is called bone marrow. Bone marrow. Bone marrow is where all of
these blood cells are made. It's the site of hematopoiesis. Hemato means blood and poiesis means to form or to make. Hematopoiesis is just a scary Greek word that means to make blood. Let's take a look at what goes
on inside the bone marrow. What's interesting is that as different as all of the blood cells are they all actually originate
from the same cell and that cell is called a
hematopoietic stem cell. This stem cells gives rise to all of the different cells
that you see in the blood. It gives rise first to two
different cell lineages or two different cell groups. First there is the myeloid group. Myeloid group. which is different from
the lymphoid group. The lymphoid group. All of the cells that you see in the blood belong to either the myeloid group or the lymphoid group. The lymphoid group includes two different types of blood cells. First there is the T cell or actually that's too big because this is a very little cell. That seems about right. There's a T cell and
the majority of the cell is taken up by the cell's nucleus, and that's what I'm shading in over here. So much so that this cell has a nickname. It's often referred to as a naked nucleus because it looks like the nucleus isn't surrounded by very much cytoplasm. This is a T cell or a T-lymphocyte. T-lymphocyte. It's very similar in appearance to the other type of lymphoid cell. This cell also has a nucleus that takes up the majority of the cell and this cell is a B
cell or a B-lymphocyte. B-lymphocyte, lymphocyte. Those are the two different
types of lymphoid cells. What about the different
types of myeloid cells. For starters we have a red blood cell. I guess we should draw that in red. This is also very small cell. I'm gonna shade in this cell so that I can show you that
the center of this cell is much lighter than the edges or the periphery of the cell. This is not the cell's nucleus, guys because we know that red blood cells don't have nuclei. What I'm trying to show is
that the center of the cell is much lighter than the
periphery of the cell. I guess I could do a better job of that if I showed you what this
cell looks like on its side. This is what a red blood cell looks like when it's laid on its side. It kind of looks like a dumbbell where the edges are much thicker or much wider than the center. The edges would since they're thicker they would be much more
densely packed with hemoglobin. Since we know that hemoglobin is what gives red blood
cells their red color, the edges would then be
darker than the center. Since the center is much thinner it would have a lot less hemoglobin. It would be a lot paler in comparison. We said that this is a red blood cell but since in science we never use a plain and
ordinary name of things we call this an erythrocyte. Erythrocyte which is just a fancy name for a plain old red blood cell. What are some of the other
types of myeloid cells? We have this one cell that
I'm drawing in over here. You might say well, that
looks nothing like a cell and you'd be totally right. This is a very odd-looking,
very large cell and it's called a megakaryocyte. Even if you never heard
of a megakaryocyte before you may have heard of
what it gives rise to because a megakaryocyte gives off little blebs of its cytoplasm to form this small cell fragments and these fragments
are known as platelets. You may have heard of
the platelets before. The rest of the myeloid cells are actually different
types of white blood cells. For example you have this
one type of white blood cell and the rest of these white blood cells are about twice the
size of a red blood cell so that looks like it's twice the size of a red blood cell to me. This cell is called a monocyte. It's known for having this nucleus that's in the shape of a kidney bean. That kind of looks like
a kidney bean to me. This is a really cool white blood cell because it protects us from bacteria and viruses and other invading organisms just like any other white blood cell does but it does so in a very interesting way. Let's say that this was a bacterium or actually, no I like the color pink so let's use a color I don't like. Let's say that this was a bacterium. The monocyte would defend us against it. It would attack this bacterium by engulfing itself around the bacterium. When it does that it kind of looks like it's eating the bacteria. It looks like its eating the bacterium. That's a very interesting way of dealing with these invading organisms. Let's clear out that. Mono actually refers to the fact that this cell has a nucleus
that's in one piece and I guess a lot of
these cells have nuclei that are in one piece. It makes us wonder what types of cells have nuclei that are not in one piece and that would bring us to a neutrophil. This is a neutrophil. A neutrophil. It has a nucleus like I'm drawing in that is broken up into several
different pieces or segment. The segments are still held together by little pieces of string. This is called a multi segmented nucleus. Even if you've never heard
of a neutrophil before I'm sure you've seen them before and how do I know that? It's because neutrophils are actually the main component of pus. If you like anybody else
has ever popped a pimple you've looked at a bunch of neutrophils. What are the other types of myeloid cells? Well, we have this one cell
that's called a basophil. Basophil. It looks something like this. You might say, well, that looks an awful lot like a monocyte and you'd be completely correct except this cell has a very unique feature that the monocyte doesn't have, and that is that it has
these bright blue granules in its cell's cytoplasm. That make it stick out. The way I like to think
of a basophil is like a basophil is like a blueberry muffin and that reminds that it has these bright blue granules in
its cell's cytoplasm. For the last type of myeloid
cell we talked about. Whoops. For the last type of myeloid
cell that we talked about is an eosinophil. It's an eosin-O-P-H,
P-H-I-L, eosinophil, okay? It has a nucleus that
can sometimes be found in two pieces. This is the first piece and
this is the second piece but that's not what makes it so unique. What it's really well known for is the fact that it has these bright, beautiful red granules
in its cell cytoplasm. Those are all of the different blood cells with all the lymphoid cells on this side and all the myeloid cells on this side. It turns out that all of these cells don't directly develop from
hematopoietic stem cell. Instead they undergo multiple
stages of development to mature into their adult form, but don't worry guys
we're not gonna hash out each of those different
forms and their names and physical characteristics. Instead we're gonna make
a very general statement. I guess we could put that up here. We're gonna say that the immature forms. the immature forms of all these cells are called blasts. When the blast mature, they mature they are called cytes. Let me show you what I mean. To spare you guys the agony of having to watch me draw out all of those different forms I just pasted them in here. We can see here that what we said about the immature forms being called blasts and the more mature form
being called cytes is true. The T-lymphocyte develops
from a T lymphoblast just like an erythrocyte develops from an erythroblast and a megakaryocyte develops
from a megakaryoblast. You guys get the pattern. The only wrench I'm gonna
throw into this pattern is with the neutrophil,
basophil and eosinophil which all actually
develop from the same cell and that cell is called a myeloblast. I think that that's a reasonable place to end our discussion on hematopoiesis.