one you see in this main image here. Well let's
move on now and have a look at the macrophage.
Macrophage is a very important cell in connective
tissue and also in other parts of the body,
that we will see and learn about as we move
through this histology course. They are phagocytes,
meaning they wander through tissues and they
mop up cell debris. They can mop up rubbish
that is produced by the cell and exocytosed
by the cell. They are street sweepers in
the body, just like the street sweeper that
wanders around and mops up the debris in our
streets, macrophages wander through connective
tissue and mop up all the rubbish and debris.
And you can see them here in this spread of
connective tissue. They have, at the electron
microscope level, very fine little pseudopodia
or extensions and that enables them to wander
through the tissue and grab hold or endocytose
all the components of the cell debris. And
then, they ingest that debris and they have
lysosomes within them and they break all the
debris down. Well normally, macrophage is very hard
to identify. So histologists used a very very
clever technique to find them and to show
them in histological sections. In this image,
this section has been taken from an animal
that is being injected with a vital dye such
as trypan blue or even carbon particles. So
now you can see the macrophages because you
can see the ingested carbon particles or blue
dyes that has been used or injected into the
animal, prior the animal being sacrificed and the
tissue processed. On the small top image,
you can see macrophages and they have a very
firm appearance. And this represents the
digested debris inside their cytoplasm. Sometimes
macrophages are called phone cells. They get
called many names and I will introduce you
to those names as we move through this histology
course. One very important job of the macrophage
is that it has on its surface special proteins.
The major histocompatibility complex too is
on the cell membranes of these macrophages.
So when these macrophages meet a foreign cell
and ingested and break it down, the macrophages
then expose antigen on the surface of these
major histocompatibility complex proteins.
And that alerts these antigens to the T-cell.
The T-cell can then identify these antigens
and then start or initiate an immune response
against these foreign cells, foreign antigens.
So macrophages, we are going to come across
a lot when we look at histology of tissues
and all the organ systems. They are
very very important cell.