I think we should be happy with H&E staining.
That's going to be the bulk of your sections
as they'll say it a number of times.
But it does have limitations.
Have a look at this slide.
On the left-hand side is a partial section
or a partial transverse section through a very small artery.
In the middle, you see a whole heap
of little, tiny dark bright pink,
bright red in fact, stained cells.
They're red blood cells passing through the
lumen of this artery.
The pink-stained area forming the wall of the artery
actually contains a number of different tissue components.
Going into higher magnification as you see
on the smaller right-hand image
doesn't give you detail of what these components are.
In fact, in the wall of that artery there,
there is smooth muscle, there is collagen,
there is connective tissues, there is even
And you can't differentiate those tissues
in a normal H&E staining section,
and that's why I say at the top it has its limitations.
But have a look at this slide.
Using a different stain, you can get differential
Here, a trichrome stain is used, 3 stains
are used together.
And now look at the blood vessel.
It's a similar section of the blood vessel
and again, the red blood cells are a browny
red in the middle, but you start to see bluish
and reddish components in the wall of the
artery and even on the outside of the artery,
you see this rather flimsy bluish tissue.
That trichrome stain is distinguishing between
collagen which is blue
and smooth muscle which is stained that
browny red color.
The smooth muscle in the artery wall is going
to contract or relax and alter the dimensions
of the artery and therefore, the amount of
blood flow through it.
The collagen is supporting the artery, making
it strong so it doesn't burst under excessive
blood pressure hopefully and normally.
If you look clear into that, you'll see a
wiggly little line towards the center
or at least towards the lumen of the artery.
That's the elastic lamina.
So this differential staining introduces me
to tell you that certain other stains that
I'll briefly describe show you various components
of tissues that enable you to describe in
more detail what tissues are composed of rather
than just relying on an H&E description.
Masson's trichrome is a common stain that
we use to distinguishing some components,
particularly to distinguish muscle from collagen
and you can read through that quietly on your own if you like.
It just gives you the basis for what a Masson's
trichrome stain does show you.
Here on the left-hand side is a high magnification
of what I described previously.
Collagen or connective tissue is blue and
the smooth muscle is the pinky reddish color.
On the other side, on the right-hand side,
a different trichrome stain is used,
a different combination of stains.
It doesn't matter what they are, but again,
they show you collagen as blue,
smooth muscle is a greenish yellow color,
but it does distinguish
that the artery wall is made up
mainly of those 2 components.
Here is a similar trichrome stain.
This happens to be a very high magnification
picture or image of the wall of the gut.
The bottom part shows you 2 layers of smooth
muscle, staining a light browny pink color.
The connective tissue that supports the epithelium
which is above the image and out of view
is stained a greeny color, and the red blood
cells can be seen in a blood vessel.
They're staining an orangey reddish color.
Another example of a trichrome stain and a
different combination is used, again,
the details I don't want to go into
to show you this differential staining.
Here is another example of a different stain
In this case, a Silver stain is used and it's
commonly used in looking at nerve tissue.
It demonstrates processes of neurons and it
also shows you the neuron cell bodies.
This is a very dark stain section, but all
those black thready-like structures you see
scattered and stained a dark black color are
nerve cell processes, axons and dendrites.
You'll learn about that when you look at the
Towards the bottom, you see a row forming
an arc of very large stained Purkinje cells,
and they're obvious because of the silver
stain that shows off this dark black type
appearance of their cytoplasm.
And the browny stain shows you the nuclei
of the neurons and other supporting cells
in the background.
Another Silver stain is used, it's not so
common now, but it's used to visualize
nerve fibers, particularly nerve fibers that are
in the cerebellum,
interneurons in the Nervous System,
interneurons of other bulk of cells
in the Nervous System that connect different
neuron-transmitting networks together,
and in this slide, you can see the neuron
cell bodies and supporting cells, or glial cells,
are stained a dark color, but you can make out very fine threads of the nerve fibers
using this particular Silver stain.
On the left-hand side is a section through
the spinal cord.
It's stained to show up myelin,
and myelin is insulating,
fatty material that goes around neurons—not blood vessels, neurons.
It's just similar to the very fine piece of plastic
you have wrapped around your copper wires.
The copper wire transmits the electrical impulse
and the plastic sheath around it is similar
to the myelin sheath you see here.
It insulates the nerve fiber just as the plastic
lining insulates the copper wire thread.
That myelin is stained in this section and
on the left-hand side, you can see a central
butterfly-shaped structure and an outer part
of the spinal cord.
It shows you, it distinguishes you
2 parts of the spinal cord,
the inner gray matter and the outer white matter.
And on the right-hand side, you can see
all that dark stain material
represents the myelin wrapping around cell processes.
You can see a large neuron in the center staining
a pale color and all that dark staining
is the myelin stain, again,
around all the neuron cell processes.
Osmium is sometimes used to stain the lipid
layers, particularly around myelin.
If you look at all those little round
circles in this image,
they're in fact axons or cell processes.
This is a section through a peripheral nerve,
and know cell processes or axons
could be sensory or motor nerve fibers travel long distances.
I've already explained in a previous lecture.
All this surrounded by this myelin which is
secreted by a supporting cell
called a Schwann cell, and as I said earlier, this myelin helps to insulate the cell process, the axon.
It's retained, preserved by osmium whereas normally,
it would be flushed out during processing if you didn't use osmium
as first of all a fixative and later on,
you can use it also as a stain.
On the right-hand side is a large nucleus
belonging to a Schwann cell
and it's wrapping layers of myelin around that
very clear structure, the nerve axon.
And a particular nerve axon passing all the
way down a peripheral nerve
is myelinated by many, many Schwann cells.
On the left-hand side, you can see a whole
host of axons through a peripheral nerve.
The axons appear as a tiny, little black dot
and they have this white halo around them.
That white halo represents where the myelin
would be if it was fixed with a fixative
such as osmium that retains that myelin.
If it did retain that myelin, then you'd see
similar to what you see on the right here.
Inside, you'd see a black layer of myelin
wrapping around those individual axons.
Another stain commonly used in neural tissue
is a Luxol Fast Blue or a Kluver stain,
and it's also commonly counterstained with H&E.
So sometimes, you can use a number of stains together
or in combination to show up various components.
And here basically, all the blue stained material
you see belongs to the fibers, the myelin
around nerve processes or it could be red blood cells
and the violet or pinky, reddy, purply stained components represent the neuron cell bodies.
Again, that's been counterstained.
Here is a marvelous slide.
On the left-hand side is a section through
the prostate gland.
It's a gland in the male reproductive system
and prior to ejaculation, the prostate gland
is going to contract and offer its contents,
prostatic secretions, into the seminal fluid.
Well, to contract, it needs muscle contracting
within the gland itself and if you look carefully
into that section on the left-hand side, you
can see some epithelial cells that are making
the secretory product, but you'll also see
yellow-stained smooth muscle cells supported
by collagen or connective tissue which stains
pinky red, and that stain is brought about
using the Van Gieson staining technique.
Probably better shown on the right-hand image,
this is a section through perhaps part of a limb.
What you see on the bulk of this section on
the right-hand side is yellow-stained skeletal
muscle enclosed by little fine strips or coverings
of red stained collagen or connective tissue,
particularly on the right-hand side, and those
thin pink stained connective tissue elements
divide these skeletal muscle into
muscle bundles or fascicles.
You'll learn about this when you do muscle
in more detain.
But in this central area, you can see 4 or
5 transverse sections through blood vessels,
arteries, and the wall of the artery
again is stained yellow
because the wall of these arteries,
these are muscular arteries.
The wall is predominominantly smooth muscle,
so muscle, whether it's smooth
or skeletal muscles, stain similarly in this particular
But what's important is that you can tell
the difference between the muscle around the
wall of these blood vessels and collagen which
supports the blood vessel, and that collagen
is showing up in that red-stained component
you see in this particular slide.
So it's another example like we saw earlier
with the trichrome, distinguishing muscle
from collagen, and they are 2 tissues that
are often very hard to distinguish
in normal H&E sections.
And that makes histology sometimes difficult to learn
if you don't have the use of sometimes using these differential stains.
Lymphoid organs such as the spleen, lymph nodes,
consist of a very delicate network of
fibers that are houses
or platforms for a lot of immune cells
to sit or attach to and do their job.
You can see those fibers running through this
tissue using what we call a Reticulin stain.
It stains the reticulin fibers running
throughout this particular organ,
you know, the aorta shown on the left-hand side, the round circular structure using H&E.
The aorta is a very important part of the
It's the blood vessel that accepts blood
from the left ventricle
and then it carries that blood to the rest
of the body, the systemic circulation.
When the heart pumps blood
into the aorta, the aorta expands
under the pressure of that contraction of the heart.
And then when the heart is going through a
resting phase and not exerting a high pressure,
then the aorta recoils like an elastic band,
like a stretched elastic band.
It recoils and maintains pressure inside the
aorta and therefore maintains flow of blood
through the aorta when the heart is going
through a resting or filling phase.
You don't see that.
The histological basis for that when you see
the H&E section of the aorta,
you see in the middle of this image.
But you do if you stain it on the right-hand
side with an Elastic stain.
It shows you that the bulk of the middle layer
of the aorta is stained with elastic tissue
which takes up that black stain you can see.
We earlier saw that the muscular arteries
were mostly smooth muscle
to change the dimensions of the lumen
and therefore, the flow.
Here, a lot of that smooth muscle is replaced
by elastic tissue to do that recoil function
I just mentioned, and the red staining
material you see there
is going to be collagen as well as some smooth muscle.
The Elastic stains are very important stain
in some tissues to expose all the elastic
tissue within that particular tissue.
PAS Reaction staining, as you can see on the
left-hand side, is used in a number of situations.
We saw it in an earlier slide to
show you, in another lecture,
to show you glycogen accumulating in cells in the liver.
Here, the PAS staining reaction shows you
the very fine basement membranes running and
supporting these epithelial cells.
Not so much that red structure in the middle.
That's the glomerulus in a kidney and all
the red staining and pink, there is basically
basement membrane, but in the more peripheral
part of this image, the light brown colored
areas is the cytoplasm of the tubules within
the kidney and these tubules
made up of epithelial cell, are supported by that pink stained basement membrane you see.
And sometimes if you look closely at the luminal
side of these tubules, you'll also see the
pink staining because the PAS reaction also stains
parts of the glycocalyx that lines these epithelial cells.
Finally, the last couple of stains I just
want to show you is a blood stain.
The Giemsa stain is used for staining blood
cells and here, you can see red blood cells
are stained and you know they don't have a
nucleus, but the other 2 cells you see,
you can see various stains show up various components.
So nucleus is that bright blue, dark bluey
color to violet color,
whereas the cytoplasm is really a paler color and the erythrocytes stain is pink color,
but the Giemsa stain is used to show up really the nuclei
because you can see that the nuclei are quite
different in some blood cells and that enables
them to be distinguished, the nuclei.
The Giemsa stain aloso shows often the
different granules within blood cells
and that again is used to differentiate
some of the blood cells.
It's a common stain for blood cells.