Well let us first of all
look at erythropoiesis,
the lineage that gives rise to our red
blood cells. Those very important cells
that transport oxygen and carbon dioxide throughout
the body within blood vessels. Well, it is important
to understand that there are a number of stages
in erythropoiesis and again let me stress
they arise from the megakaryocyte or erythrocyte
progenitor cell. Have a look at the slide
on the right-hand side, in one of the most
fascinating things when you study histology,
You see some very very pretty slides.
Very pretty stains, very pretty demonstrations
of tissue. I think bone marrow is one of the
prettiest tissues to look at using standard
stains under the light microscope. Well, when you
look at the slide, you can see some red blood
cells that have maintained their mature red
blood cells. All those small pink reddish
or orange stain structures are erythrocytes.
They are matured, they are circulating in
the bone marrow and they are leaving the bone
marrow to enter into the general circulation.
They arise from the proerythroblast. This
is the very first stage of the progenitor
cell then starting to form what would be the
final erythrocyte. These proerythroblasts
are large cells. They occupy a diameter of up
to 20 microns. So they are big cells and
one thing to bear in mind is particularly
when you look at lineages of this cell and
the neutrophil later on is have a think about
what the end product is going to be.
The end product is going to be the red blood cells
that you see also in this image.
They are much smaller cells, they are only about 6
to 8 microns in diameter. So when the progenitor
cell gives rise to a proerythroblast, it is
a large cell that is eventually going to go
through the differentiation process and finally
end up being just a little package of hemoglobin.
And that is essentially what a red blood cell
is. So when you see these large cells, they
represent the very busy activities of these
cells and I will refer to that as we go through
this lineage. The proerythroblast has a mild
amount of basophilia. Suddenly the progenitor
cell has given rise to the proerythroblast.
It is going to now start, going through the
process of making hemoglobin. But initially
they just has a mild amount of basophilia.
Well the next stage in the process of forming a
red blood cell is differentiating into what
we call the basophilic erythroblast and that
is shown on this particular cell here. And
basically if you look very carefully in the
cytoplasm, there is stronger basophilia that
you saw previously in the proerythroblast.
And then again as I said earlier think back
as to what the destination of the cell is
going to be. It is going to be a red blood
cell. It is going to be containing a whole
lot of hemoglobin, the protein carrying oxygen.
So initially, back in the early cell stages,
you would expect to have a cell that develops an
enormous amount of rough or granular endoplasmic
reticulum to make that protein hemoglobin.
So at some stage and that's stage you see here,
the cell has accumulated all this endoplasmic
reticulum, which takes up the basophilic stain.
So here is an indication now that this cell
has been activated to start making hemoglobin.
It has a factory now to make that hemoglobin.