Histology is the science of studying tissues, and cytology is the science of studying cells. The word 'histo' means tissue, 'cyto' means cell, and 'ology' means science.

To study cells and tissues, we need microscopes to magnify the small parts that cannot be seen with the naked eye.

Most tissues and organs are very thick so the light of the microscope cannot penetrate them, so we need to cut them into very thin and transparent sections to be able to see them under the microscope.

God willing, today is the first lecture

Study of tissues and embryology

With you Dr. Mohamed Khaled

We continue together God willing throughout the journey. Ah, the histology journey

Histology is a very light and easy subject if understood. And remembered

Correctly in the right way. So we continue like this together God willing and focus

Together like this in the lecture. Let's start in the name of God, the Most Gracious, the Most Merciful from ah

Histology and cytology. What does histology mean and what does cytology mean?

Histo comes from an old Greek word meaning tissue

And cyto comes originally from an old Greek word also meaning cell

Sali

Ology means science

So we study the science of studying cells and the science of studying tissues

Okay, how do we study cells and how do we study tissues?

And what exactly is the science of studying cells and the science of studying tissues?

Because we have different required procedures. We have a matter, we have cell study

And we need a microscope to magnify many times what we see with our eyes

We need microscopes and we need the structure of cells

How with a microscope, how do we work with the microscope? Okay, ah

It says that most tissues and organs are very thick so the light

Of the microscope cannot penetrate them, so we need to make the tissue and organ

Very soft material, very thin material so that the light can penetrate it

And we can see under the microscope

It should be transparent

It should be thin enough to be transparent

You can see through it

It should be clear but you can see through it

It should be through it

Then thin

Transparent

Thin transparent sections

And we cut them from it and put them on glass

And put them on glass

So that we can make

The internal structures.

The most famous method to prepare tissues for the light microscope is the paraffin technique, where the tissue is placed inside paraffin which is solid at room temperature.

Paraffin is melted to embed the tissue inside it, then cooled to become solid, because the tissue is soft and cannot be cut easily without the solid paraffin.

For light microscope preparation, the paraffin technique is the most commonly used technique. Of course, we

Need this, the matter is not random. It's not that I take the sample from the body or from anywhere and put it on a piece of glass and cut it until

And that's it, the matter is finished and I will see the world. No, I need techniques.

I need techniques, methods. Ah, skills. To know how to do all these steps.

And the most famous method used is paraffin. So what is paraffin?

Paraffin is a solid material. Ah, at normal room temperature it is

Very solid material. What do we want from this paraffin? We want

Initially, we put the tissue inside the paraffin. But how? How

And paraffin is solid. So we need to melt it, liquefy it so that

We can put the tissue inside the paraffin, plant it

Inside it, then we put the paraffin at room temperature and cool it

So that it becomes solid and we can cut the tissue. So why don't we cut

The tissue without paraffin? Why do we need paraffin? Because the tissue is soft

We want it. So we need a solid material so we can cut it well.

Let's take it with some detail. And take it step by step. And the father of the step with us

What is fixation for the tissue we get?

The first step in tissue preparation is fixation to preserve the tissue from autolysis and bacterial decay after it leaves the body.

Fixation is done using formalin which preserves the tissue and makes it firmer to facilitate cutting.

We need to fix it and preserve it

We preserve the tissue

From what do we preserve it?

We preserve it from the

Because as soon as the cell or tissue leaves the body it will start to break itself down

Auto means something automatic

Lysis means automatic breaking down

It breaks itself down

So we protect it from this

We protect it from putrefaction

From decay and decay from bacteria

Of course, there are bacteria in the air

There are bacteria in the tissue itself

So as soon as it leaves, it loses all protection

So it can get infected by bacteria

And we lose the normal tissue and lose everything

We make it harder by fixation

We need it by fixation

By fixation it will be harder

So we can cut it more easily

Okay? Okay

So in order to be able to cut

Will we take it out of the body

And it will remain in its natural state like that, okay?

And I will see my cells and my structure and my arrangement and everything

No, of course, as soon as it leaves the body it was in a certain environment and you took it to another environment

So all of that goes, all of that breaks, all of that disappears

So we need to fix it first

Preservation

We do preservation

After we do preservation

What do we do preservation with first?

Formalin, which is the material we preserve the tissue with

The same material we preserve tissue with in anatomy

We preserve the tissue here in histology

With formalin

Okay

After we put the formalin material and preserve it

We wash with water

With water, look, look

We wash with water because

There is some excess formalin

That needs to be removed

This is the second step

Third step

Dehydration

The next step is gradually removing water from the tissue using alcohol, because paraffin does not mix with water and the tissue needs to be free of water to be immersed in paraffin.

The tissue is cleaned with alcohol gradually in increasing concentrations (70%, then 80%, then 90%, then 100%) to avoid cell damage.

What does dehydration mean?

It means water or moisture, dehydration means removal or elimination. So removal of water

Removal of water. What water? What water do we remove? And why do we remove the water? What

Is the harm in water? The tissue already has water. Okay? The tissue already

Has water. So why do we want to remove water? It says that paraffin

Is hydrophobic, meaning it fears water, it fears water because we

Need to do what? We need to put the tissue in paraffin. But paraffin

Fears the tissue that is in water. So I remove water from the tissue to put

It inside paraffin. Okay? So I need to remove water from the tissue.

So gradually. So that it has the ability to mix. Mix or

Be mixed with the tissue. Okay? Simply. Okay, fourth step. We add or wipe.

What exactly do we wipe before we know? We wipe what? We were cleaning

The water with what? We use what? We use mild alcohol that fits our conditions

This is what we use, regular alcohol, we wash it, we clean it

With alcohol. It says also there is exposure. So also alcohol is exposed

With paraffin. It does not know that paraffin cannot enter

Into it, alcohol. So how do I clean the water? I have nothing but alcohol. So

I have, ah, what do I do? I clean alcohol with another material, with a third material

Completely. Ah, for example, we clean it with 70% alcohol. Then

80%, then 90%, then 100% alcohol. Gradually, gradually so the cells do not shrink. They shrink from

They are scared of alcohol. We do it one by one, one by one, one by one. We don't put

In 100% water at once. No, we put 70, 80, 90, and so on

Gradually. We go to the fourth step.

It's called xylene, it cleans alcohol. So what does xylene do exactly?

What is the function of xylene? Xylene liquefies paraffin. Meaning

Xylene is used to remove alcohol from the tissue and dissolve paraffin to make the tissue more transparent and allow paraffin to enter the tissue.

It melts, dissolves paraffin. So that the tissue is ready to enter

The paraffin. We said we need to melt it, no, it won't work

It won't work, it must remain solid. It won't work to melt it so that

The tissue can enter inside. So we melted it with what? With xylene. We cleaned

The alcohol. So xylene has three functions: it removes alcohol,

And melts the material we need to put in, and makes the tissue

More transparent. So it knows what? Its dye can penetrate it more because

It is called clearing

It wipes

Alcohol

It wipes or melts

Paraffin, making the tissue

More transparent

More

Transparency

And then

Who will I load? Paraffin with what? With tissue. What do I do? I plant what? I plant

The tissue. Where? In paraffin. I give the fifth step that I plant.

After dissolving paraffin with xylene, the tissue is implanted inside liquid paraffin then cooled to become a solid block containing the tissue.

The paraffin block containing the tissue is cut into very thin slices using a device called rotatory microtome, then placed on a glass slide.

How is it done? Or exactly how is it done? We put the tissue in what

We melted it with? With xylene. Okay? We melted it with, ah,

We made it ready for something to enter inside the tissue

And we put it and finished this is the fifth step with me

They became what?

Solid block

After we melted the paraffin we return it again

To room temperature so it becomes solid

We made it solid, finished, the matter is done

We reach the sixth step, cutting

What do we cut it with? With a machine called

Rotatory microtome

Ah, rotatory microtome, I will show you rotatory microtome, the same unit

Rotatory

Ah rotatory microtome, I'll show you rotatory microtome, the same unit.

Rotatory.

This is the rotatory microtome. You see it's called rotatory because it rotates.

Here like this. Here in this place it keeps rotating. It keeps cutting. Here it is.

Do you see the sample? What is the sample? You heard rotatory microtome, we put the sample in it.

And it starts cutting very thin sections. After cutting the very thin sections.

These are from paraffin and from the tissue, I start putting them on slides.

The slices are similar in color and shape so we need to stain them using special dyes called stains to facilitate distinguishing between tissue components.

How is the cell? And all the cells look alike. Like I got a white piece in the blacks here, I don't know how to differentiate this or that, or know what this is.

Or what this is, or if this is separate or if this is tear or that is tear. I need to.

The stain. The stain is what? The stain is the stain. Okay.

Ah, this stain. What is the stain? Like a stain.

I will talk about the stain now but let's talk about the nature of the stain.

What is this stain? What exactly is the stain? The stain is water. The stain is water.

Okay? So who doesn't like water? The outside. So we don't know.

We melted. Okay, we cut the slide and the matter ended and we put it on.

Glass. So we finished all the previous steps. We will go back in reverse.

We will start from when? From when we did, let's say, from what we did until washing.

Until the water. What did we do first? We removed with washing. After.

That we did with alcohol. We removed the water with alcohol, so water. We removed it with alcohol.

We did with xylene. That is, we froze with the thing. We will do the opposite now.

We will remove the xylene. What remains? What remains is the alcohol. The alcohol. The alcohol. We will remove it.

Also gradually so that it doesn't happen as we agreed. What remains? What remains.

Water. We will keep this water for what? So that we can get the stain inside.

The paraffin. Inside, not paraffin, at the time we cut the paraffin completely. Inside.

The tissue. Okay? We put the stain, we will review the process again.

We will go back, remove the water so we can keep the paraffin. We remove the water.

With alcohol and remove with xylene and freeze.

Again. Put the paraffin at room temperature. And it will be what? With tissue again.

Okay? Ah, it tells you that this is aqueous stain, meaning its nature.

Is aqueous. So we need to return the water in it again. Then remove.

The water again. After we finished staining, after we returned the water.

We stained, removed the water again. Okay, the last step completely is covering with something called.

After staining, water is removed from the slices again using alcohol and xylene, then covered with another glass slide (cover slip) to protect and prevent contamination.

Cover slip. Cover slip means after we put a piece of glass we put another piece.

Of glass on it to prevent what the subscriber from it to scratch what the subscriber from it to avoid contamination by bacteria, yes, its percentage.

In its place so it doesn't slip and also provide a good environment for the microscope.

Types to enter through it, a clean environment, a suitable environment for the microscope.

To enter. It gives us a suitable clean surface for the microscope. This was.

This was the first part of the lecture with us. God willing, we will continue explaining the first part in the second.

Part. We will continue with the stains and types of microscopes.

A very delicious topic and very interesting. I, like the autopsy, really enjoy.

Again while I explain this stuff. Ah, I enjoy that it mentions all this.

With you. And I enjoy explaining it to you. I try to convey it to you and God willing it will be.

Conveyed in the best way. And you understand it before you are motivated because.

Motivation will come by inference. I understood, I will infer, yes. That was like this, ah. So.

After that I must do this. After that I must do that. And inferential steps like this.

Light and gentle. God willing, see you in the next lecture.

See you well. Peace, mercy, and blessings of God be upon you.

A brief and light conclusion. God willing, I'll see you in the next lecture.

See you well. Peace, mercy, and blessings of God be upon you.